(via Gem & Jewellery News, Vol.13, No.1 March 2004) Harry Levy writes:
It is amazing how little those who use grading certificates understand exactly what they are using. Laboratories, amongst the other work they do, produce two types of certificates. The first is an identification report, telling one whether it is a natural stone or a synthetic one, some identify whether the stone has been modified by treatments other than cutting and polishing, and some may give an origin of the stone, where the stone has been mined.
The other type is a grading report, usually for diamonds, which gives a grade for the color, clarity and other relevant factors to identify the stone, such as its dimensions and shape, as well as comments on cut and proportion, and an indication of fluorescence should this exist. Sometimes these reports are called grading certificates, which is an incorrect description. The grading reports may now include comments on treatments, a topic on which there is yet no universal agreement. Some identification reports are now trying to give comments on the amount of treatment a stone has undergone, for example the amount of oiling or resin-filling an emerald has been subjected to.
Why use reports?
The question to ask is why do we need grading reports and the simple answer is that they are used to put a value on a stone. It makes it simpler to compare stones, both for matching and for pricing. I recall when I first started trading in diamonds I would get a phone call with the question: “How much is a 1 carat diamond?” No matter what answer I gave I was told that they could get it cheaper and it was only after a second discussion could I tell them the price was dependent on the quality and thus give myself a chance of selling a stone.
Today I still get similar calls, although the enquiries seem to be more specific. I am now asked to quote for, say, a one carat diamond of color G and clarity VS1, again when I give a price I am told they can get it cheaper. The potential buyer thinks that by giving the parameters of color and clarity he has totally identified the stone. If I can get back to the caller I ask him he has such a stone and can he measure the diameter of the stone. If he can, I tell him his stone is of diameter of about 6.1mm. I am often asked how did I know and the simple answer is that a well-proportioned carat stone is of diameter 6.5mm and if he is being offered a stone below market value then there is a reason for this in that the stone is too deep or too flat, he has not considered the cut. Price is affected by the amount of fluorescence and the proportion of various facets. Price is also affected by the quality of the rough from which the stone is cut. Grading reports capture as many parameters as they can, but ultimately the final factor determining value is how the stone appears to the eye. One needs much experience to make these subtle judgments.
I have written much in the past about how we have come to have the terminology we use in diamond grading. The most popular system is that used by the GIA of letters for colors and terms such as VVS1 and SI2 for clarity. Other systems are used, using more descriptive terms but some such reports may have a chart showing how their system relates to the GIA one.
All this looks well to most traders, but unfortunately the comparison is not so simple. The main problem is that the sets of master stones used to determine color in different laboratories are not identical. Color is determined by using a trained eye to compare the stone with two adjacent master stones.
In some laboratories a stone that falls between the G and H master stones (i.e. worse than G but better than H) is considered to be G, whereas in others it is the stone between the F and G master stones (i.e worse than F but better than G) that is graded as G. Superficially these two systems seem to contradict each other, but if the G master stone in the one system is the same as the H in the other system then they are both seemingly coming up with the same answer. Thus when determining a master stone set the laboratory can claim that their master stone G, say, is a bottom G or a top G. But how these master stones sets compare to each other is something that is somewhat unknown. A similar problem exists for grading clarity.
The international diamond community tried to reconcile these problems by setting an ISO standard for diamond grading. An analogous problem could be for giving the weight of a stone. It is like some taking two stones of almost the same weight and saying that anything that falls between these two weights is identified as the weight of one of them. Thus if this was the method of determining weight, one could buy a stone in one place and be told that it weighs one carat, and when taken home and weighed again it was found to weight only 0.95 carat. Such ambiguity would be intolerable and, by convention, we have internationally recognized standards for weight. The ISO standard tried to achieve a similar convention for grading diamonds, bringing together the main systems used in the world. After 15 years of hard work the proposed system was not accepted.
Many in the diamond community would like to see such a standard adopted. This would help remove ambiguity and make the comparison of diamonds much easier. Unfortunately trade laboratories do not want to have their system replicated for outside use. Different centers use their own systems for grading and in order to buy and sell in these places one has to use the local grading report, and if one the goes to another center the stone may have to be regarded locally for the traders there. Imagine if one had to do this for weight! This was indeed done for many years from the early 1900s until the metric carat became standard. In many diamond centers one had to obtain an ‘official weight’, either through a local laboratory or a local trade organization. This problem no longer exists for weight, as most dealers now have accurate weighing balances, although the weight in a grading report still has a degree of being more official and thus acceptable than the weight given by the trader.
Thus the most pertinent question, whenever one is given a grading on a diamond, is to ask “Who says so?” Internationally some reports are more acceptable than others, although this can vary locally. If you have followed the arguments so far, you will probably see the need for one acceptable world standard. But I will try to show that even adopting a world standard we will still have ambiguity within the system.
Let me talk about the SI3 debate. The clarity grading for diamonds is accepted to be:
IF: Internally flawless
LC: 10x Loupe clean
VVS1 and VVS2: Very very small inclusions
VS1 and VS2: Very small inclusions
SI1 and SI2: Small or slight inclusions
P1, P2 and P3 or I1, I2 and 13: Visible inclusions
Many traders think that the band classified as P1 is too wide. That is, too many stones of different clarity appearance fall within this grade. One must remember that the grades determine the price and some stones within the P1 band look much better than others within that grade. Thus stones within the same grade could sell for significantly different amounts and traders wish the grading report to somehow show this differential. Some traders began to call the better P1 stones SI3. This new classification has been accepted by bodies such as the World Federation of Diamond Bourses (WFDB), many laboratories use it and it is shown on the Rapaport price listing grid. Other trade organizations and some of the major laboratories refuse to recognize this new grade.
The laboratories who refuse to use it claim that an SI stone has inclusions which are not visible to the naked eye, whereas P stones (pique stones) have inclusions which are visible to the naked eye. Bringing stones which have visible inclusions into a classification for stones with inclusions that are not visible will introduce a contradiction into the term SI. Further they argue it will be difficult to define the term SI3 for international use. Then there are those within the trade organizations who feel any changes in the rules will only confuse the trade and the public. They fear retrospective complaints. Thus a stone given a grade at one time could obtain a different grade if it is graded again. Although giving a stone a SI3 grade may be better than calling it a P1 stone, then some stones graded as SI2 may now be graded as SI3.
The reason that the terminology SI3 is being used is that for most traders it is easier to sell a stone with an SI grade than a P grade. This is because we have degraded the stones that have visible inclusions and there is a reluctance to buy a stone with a P grading. In fact very few stones with visible inclusions are graded as the report in most cases will hinder rather than assist a sale. Many dealers will not pass on a report which has a P grading. Thus they are opting for an SI, thinking that this will make it easier to sell the stone. What in fact is the case is not that it is called an SI stone but that it is no longer P1. Not being a P1 is the important criterion. We can call these stones anything we want, for example we could call them VI stones—visible inclusions.
I said above even if we come to agreements to have an ISO standard for diamond grading there are inherent problems within the system. Our grading system has all the trappings of being a scientific system; it has well defined terms, it is subject to measurements and we make use of scientific instruments, and work is done in laboratories by people with scientific qualifications. But at best it is a pseudo science. It is this because it does not really have well defined terms. Linguistically terms used in diamond grading are vague terms. The colors D, E, etc, have all ill-defined scientific basis. They indicate color but are based on only a vague concept of absorption of light. The whitest stone, i.e. the one with the least color, was taken to be D, a stone with a perceptible difference in color was taken as the next stone and called E, and so on for F, G, etc. There is no scientific relationship between the colors D, E and F. We can do this with weight. A 3 carat stone is three times as heavy a 1 carat stone. Also the color scale is no linear. The colors D, E, and F are closer together than the colors J, K and L.
A similar problem exists for clarity grading. The term ‘clean’ seems unambiguous, but in reality it is only clean because we can see no inclusion with a 10x loupe. Put this stone under a microscope and with sufficient magnification one will eventually find inclusions. So grading a diamond is more of an art than a science. Similarly, the terms VVS, VS and so son are again randomly chosen terms. The International Diamond Council (IDC) tried to put some science into the system by measuring the sizes of inclusions in microns. But for grading stones it was not only the size of the inclusion that determined the clarity grade but where it was positioned in the stone. This again brings the art into grading and not just a science of measurement.
Vague terms have no absolute values. Thus a very small elephant is much bigger than a very very large rat, and a spoonful of sugar varies from one time to the next. We understand these terms, we can use them correctly, but not in absolute terms such as grammes, meters or minutes. Those who argue that we cannot define an SI3 term fail to realize that they have defined, in an arbitrary way, all the terms that are used for diamond grading, other than measurements of size and weight and proportion, and introducing one more vague term into a system of vague terms is not beyond our means or imagination.
Those who argue that introducing such a term would make it easier to sell a pique stone have failed to realize that laboratories and grading reports are there to help the trade and not hinder it. Recent developments in the distribution of rough diamonds by organizations such as the Diamond Trading Company (DTC) and the shortage of better quality stones is going to result in more stones of lower grades being offered in the markets to satisfy demand for diamonds. It seems strange to degrade the quality description of such stones.
Another argument espoused by those who do not wish to change the terminology is that the change would confuse the trade and the public. I have used the term VI; this is an arbitrary term I have chosen, it is not a term I am necessarily advocating. It is somewhat provocative on my part in that some will say it is too similar to VVS and VS. The trade is remarkably adept in accepting innovation and anyone who cannot understand the terms we use should not be in the trade. As for the public, it is totally fallacious to say they will be confused. The average member of the public has absolutely no idea what a G/VS1 diamond is. It is not a terminology we are taught at school, but if a graded diamond is sold with a certificate it will have a glossary that explains exactly to him what these terms mean and how they relate to each other. Our trade is far more transparent than almost all other trades. When we look at the ingredients of a foodstuff we think we know exactly what we are eating but how many of us know what E145 is an additive?
Problems such as this and all the new treatments now being done to diamonds to improve their appearance, such as high pressure high temperature (HPHT) and the appearance of synthetic stones is causing consternation within the trade. The subject was discussed at the CIBJO Congress held in Bangkok at the end of February, and will no doubt come up at the World Diamond Council (WDC) meeting in Dubai at the end of March, and meetings being called by smaller groups in other localities. If history is anything to go by, little will be resolved, the conservatives will prevail, they will fear change and find themselves being retroactive instead of proactive. We do not want to resolve problems until they are imposed on us through forces beyond our control.
A final story will illustrate our unwillingness and inability to act. CIBJO allowed only the term ‘treated’ to be used for stones that had been processed by means other than cutting and polishing. White topaz was being irradiated to change its color into various hue of blue. CIBJO was asked to introduce the term ‘irradiated’ to describe such stones, but the term was not accepted and was banned; they had to be designated as treated. The US government brought in legislation that anything that had been irradiated had to be so declared when being imported into
the United States. This was to ensure that such stones would be tested for safety before being distributed. Declaring such stones as treated was inadequate. So CIBJO was forced to allow the term ‘irradiated’ into its lexicon, as otherwise there would not have been trade between the USA and the rest of the world in white topaz artificially colored.
I hope to report back in the next issue of Gem & Jewellery News on any changes, if any, that will be advocated by the trade in these Congresses.
Friday, May 04, 2007
Thursday, May 03, 2007
Taxi Driver
Memorable quote (s) from the movie:
Betsy (Cybill Sheperd): You know what you remind me of?
Travis Bickle (Robert De Niro): What?
Betsy (Cybill Sheperd): That song by Kris Kristofferson.
Travis Bickle (Robert De Niro): Who's that?
Betsy (Cybill Sheperd): A songwriter. 'He's a prophet... he's a prophet and a pusher, partly truth, partly fiction. A walking contradiction.'
Travis Bickle (Robert De Niro): You sayin' that about me?
Betsy (Cybill Sheperd): Who else would I be talkin' about?
Travis Bickle (Robert De Niro): I'm no pusher. I never have pushed.
Betsy (Cybill Sheperd): No, no. Just the part about the contradictions. You are that.
Betsy (Cybill Sheperd): You know what you remind me of?
Travis Bickle (Robert De Niro): What?
Betsy (Cybill Sheperd): That song by Kris Kristofferson.
Travis Bickle (Robert De Niro): Who's that?
Betsy (Cybill Sheperd): A songwriter. 'He's a prophet... he's a prophet and a pusher, partly truth, partly fiction. A walking contradiction.'
Travis Bickle (Robert De Niro): You sayin' that about me?
Betsy (Cybill Sheperd): Who else would I be talkin' about?
Travis Bickle (Robert De Niro): I'm no pusher. I never have pushed.
Betsy (Cybill Sheperd): No, no. Just the part about the contradictions. You are that.
New Technique Produces 10-carat Diamond
Science daily writes:
Researchers at the Carnegie Institution of Washington, D.C. have produced 10-carat, half-inch thick single-crystal diamonds at rapid growth rates (100 micrometers per hour) using a chemical vapor deposition (CVD) process. The size is approximately five times that of commercially available diamonds produced by the standard high-pressure/high-temperature (HPHT) method and other CVD techniques.
In addition, the team has made colorless single-crystal diamonds, transparent from the ultraviolet to infrared wavelengths with their CVD process. Most HPHT synthetic diamond is yellow and most CVD diamond is brown, limiting their optical applications. Colorless diamonds are costly to produce and so far those reported are small. This limits general applications of these diamonds as gems, in optics, and in scientific research. Last year, the Carnegie researchers found that HPHT annealing enhances not only the optical properties of some CVD diamond, but also the hardness. Using new techniques, the Carnegie scientists have now produced transparent diamond using a CVD method without HPHT annealing.
"High-quality crystals more than three carats are very difficult to produce using the conventional approach," said scientist Russell Hemley, who leads the diamond effort at Carnegie. "Several groups have begun to grow diamond single crystals by CVD, but large, colorless, and flawless ones remain a challenge. Our fabrication of 10-carat, half-inch, CVD diamonds is a major breakthrough."
The results were reported at the 10th International Conference on New Diamond Science and Technology, Tsukuba, Japan, on May 12, 2005, and will be reported at the Applied Diamond Congress in Argonne, Ill., May 18, 2005.
"The rapid synthesis of large, single-crystal diamond is a remarkable scientific achievement, and has implications for a wide range of scientific and commercial applications," said David Lambert, program director in the National Science Foundation (NSF)'s earth sciences division, which funded the research.
To further increase the size of the crystals, the Carnegie researchers grew gem-quality diamonds sequentially on the six faces of a substrate diamond plate with the CVD process. By this method, three-dimensional growth of colorless single-crystal diamond in the inch-range is achievable.
Finally, new shapes have been fabricated with the blocks of the CVD single crystals. The standard growth rate is 100 micrometers per hour for the Carnegie process, but growth rates in excess of 300 micrometers per hour have been reached, and 1 millimeter per hour may be possible. With the colorless diamond produced at ever higher growth rate and low cost, large blocks of diamond should be available for a variety of applications.
"The diamond age is upon us," said Hemley.
Note: This story has been adapted from a news release issued by National Science Foundation.
Source: http://www.sciencedaily.com/releases/2005/05/050527105139.htm
Researchers at the Carnegie Institution of Washington, D.C. have produced 10-carat, half-inch thick single-crystal diamonds at rapid growth rates (100 micrometers per hour) using a chemical vapor deposition (CVD) process. The size is approximately five times that of commercially available diamonds produced by the standard high-pressure/high-temperature (HPHT) method and other CVD techniques.
In addition, the team has made colorless single-crystal diamonds, transparent from the ultraviolet to infrared wavelengths with their CVD process. Most HPHT synthetic diamond is yellow and most CVD diamond is brown, limiting their optical applications. Colorless diamonds are costly to produce and so far those reported are small. This limits general applications of these diamonds as gems, in optics, and in scientific research. Last year, the Carnegie researchers found that HPHT annealing enhances not only the optical properties of some CVD diamond, but also the hardness. Using new techniques, the Carnegie scientists have now produced transparent diamond using a CVD method without HPHT annealing.
"High-quality crystals more than three carats are very difficult to produce using the conventional approach," said scientist Russell Hemley, who leads the diamond effort at Carnegie. "Several groups have begun to grow diamond single crystals by CVD, but large, colorless, and flawless ones remain a challenge. Our fabrication of 10-carat, half-inch, CVD diamonds is a major breakthrough."
The results were reported at the 10th International Conference on New Diamond Science and Technology, Tsukuba, Japan, on May 12, 2005, and will be reported at the Applied Diamond Congress in Argonne, Ill., May 18, 2005.
"The rapid synthesis of large, single-crystal diamond is a remarkable scientific achievement, and has implications for a wide range of scientific and commercial applications," said David Lambert, program director in the National Science Foundation (NSF)'s earth sciences division, which funded the research.
To further increase the size of the crystals, the Carnegie researchers grew gem-quality diamonds sequentially on the six faces of a substrate diamond plate with the CVD process. By this method, three-dimensional growth of colorless single-crystal diamond in the inch-range is achievable.
Finally, new shapes have been fabricated with the blocks of the CVD single crystals. The standard growth rate is 100 micrometers per hour for the Carnegie process, but growth rates in excess of 300 micrometers per hour have been reached, and 1 millimeter per hour may be possible. With the colorless diamond produced at ever higher growth rate and low cost, large blocks of diamond should be available for a variety of applications.
"The diamond age is upon us," said Hemley.
Note: This story has been adapted from a news release issued by National Science Foundation.
Source: http://www.sciencedaily.com/releases/2005/05/050527105139.htm
A Bright Idea For Diamond Miners
(via Gemmology Queensland, Vol.8, Issue 3, March 2007)
A Queensland company is putting more sparkle into the world’s diamond industry with a new device which helps miners recover more the precious stones. Miners normally sift through many tones of ore in order to find small number of diamonds.
Brisbane’s Partition Enterprises is developing a new generation of density and fluorescent tracers which makes finding the stones in the ore much easier. Dr Chris Wood, founder and chief executive of Partition Enterprises, explains than an enormous amount of waste ore has to be processes in the search for diamonds. The processing plants are adjusted to do this by controlling the density and precision of the separation, and that’s what density tracers are used for.
Density tracers, usually small cubes, have carefully controlled densities to mimic the composition of the valuable material the miner wants to recover, as well as waste. Diamonds, for instance, are of much higher density than the waste in which they are found. Density tracers are added to the ore that’s fed into the separator and, after checking which densities reported to diamond concentrate and which to waste, the separation characteristics can be calculated.
If need be, the machinery can then be adjusted to achieve optimal performance. “The alternative is to assess performance by taking large samples from the plant and subjecting them to exhaustive laboratory analyses using toxic liquids,” Dr Wood says.
“Typically these procedures take weeks to generate data. And those data are less reliable than a density tracer test, which can be completed in an hour.” But even after subjecting diamond-bearing material to density separation, the concentration of diamonds is still very low. So fluorescent tracers, which make use of the fact that diamonds glow blue when irradiated with X-rays, are used.
Partition Enterprises’ new tracers glow in the same way and they help calibrate X-ray diamond sorters to minimize any loss of the precious stones. Dr Wood believe his company, which he and colleagues at the Julius Kruttschnitt Mineral Research Center in Brisbane began to supply density tracers for the coal industry in 1980, is the world’s major supplier of these devices.
Source: http://www.smartstate.qld.gov.au/
A Queensland company is putting more sparkle into the world’s diamond industry with a new device which helps miners recover more the precious stones. Miners normally sift through many tones of ore in order to find small number of diamonds.
Brisbane’s Partition Enterprises is developing a new generation of density and fluorescent tracers which makes finding the stones in the ore much easier. Dr Chris Wood, founder and chief executive of Partition Enterprises, explains than an enormous amount of waste ore has to be processes in the search for diamonds. The processing plants are adjusted to do this by controlling the density and precision of the separation, and that’s what density tracers are used for.
Density tracers, usually small cubes, have carefully controlled densities to mimic the composition of the valuable material the miner wants to recover, as well as waste. Diamonds, for instance, are of much higher density than the waste in which they are found. Density tracers are added to the ore that’s fed into the separator and, after checking which densities reported to diamond concentrate and which to waste, the separation characteristics can be calculated.
If need be, the machinery can then be adjusted to achieve optimal performance. “The alternative is to assess performance by taking large samples from the plant and subjecting them to exhaustive laboratory analyses using toxic liquids,” Dr Wood says.
“Typically these procedures take weeks to generate data. And those data are less reliable than a density tracer test, which can be completed in an hour.” But even after subjecting diamond-bearing material to density separation, the concentration of diamonds is still very low. So fluorescent tracers, which make use of the fact that diamonds glow blue when irradiated with X-rays, are used.
Partition Enterprises’ new tracers glow in the same way and they help calibrate X-ray diamond sorters to minimize any loss of the precious stones. Dr Wood believe his company, which he and colleagues at the Julius Kruttschnitt Mineral Research Center in Brisbane began to supply density tracers for the coal industry in 1980, is the world’s major supplier of these devices.
Source: http://www.smartstate.qld.gov.au/
Diamond Grading Harmonization—New Standards
(via Gem & Jewellery News, Vol. 11, No.4 September 2002) Harry Levy writes:
The International Standards Organization (ISO) papers on diamond grading harmonization have at last been published and been sent to the participating countries to be voted on.
If the vote is passed it means that the world will have an ISO standard for grading diamonds. If it is not passed, then the working group will have to reconvene and it is doubtful if another paper will be published in the near future. It has taken over fifteen years to have reached this stage. Some of those who were involved in the writing of these papers have indicated they will vote against it. How has this state of affairs arisen and how will it affect diamond grading and the diamond trade and all those involved in selling grading certificates with their stones?
Terms for color
Diamonds have been graded for many years for color and clarity. Initially descriptive terms for color, sometimes based on geographical locations, were used. For example, we had ‘white’, ‘tinted’, ‘cape’, ‘wesselton’, ‘river’, ‘light brown’ stones and so on. There was usually local understanding of these terms and how they would be used, but there were no universal agreements. So partners in a firm, local dealers belonging to a diamond bourse or those traveling to, say, South Africa, would understand what a ‘cape series’ was, but this was very much an esoteric language. ‘White’ meant different things to different dealers, and one could rarely buy on the seller’s description only, one had to see the stone. The prominent systems to be used were the ones used in South Africa as a producing country, and consisted of terms ‘wesselton, ‘crystal’, and ‘cape’, with words such as ‘top’ added as a prefix. End users adopted and modified such systems and the above terminology was incorporated into the Scan D N grading system.
A further system was introduced top make the language less esoteric and terms such as ‘white’, ‘tinted’, and ‘brown’ were used with prefixes such as ‘exceptional’, ‘rare’, ‘slightly’ and ‘top’ being used. As an aside, stones sold as ‘blue white’ and ‘premier’ are now referred to as those that have fluorescence.
GIA system
In all its confusion an attempt was made by the GIA to introduce a grading system which was more objective than the subjective methods used. They picked on a certain number of stones of different shades, graded these by comparing them to each other ranging from the purest white (or, more accurately, colorlessness) to shades of pale yellow, gave letters to these stones and referred to them as ‘Master Stones’. They called the highest grade a D color, and graded the rest down using E, F, G and so on. There was a perceivable shade of color between adjacent stones in this series. Thus, a stone which looked more colorless than a G but less colorless than an F, was referred to as an F color.
The letter D was taken to be the best color and this was done, according to the late Richard Liddicoat (for many years Chairman of the GIA), to void confusion with letters already in use such as A, B and C. The systems using these letters had been further modified by using A+, A++, AA, AAA, and so on. D was the failure grade in American schools and as an ‘in joke’ and, on the assumption that D had never been used to denote a color grade, they made this the top color. The trade and public found this to a far less confusing system—they knew the lower the letter the lower was the color.
Clarity terms
On the clarity grading terms such as ‘loupe clean’, ‘very very small inclusions’ (VVS), ‘very small inclusions’ (VS), ‘small inclusions’ (SI), were used and these too were easy to understand. With such a system in place investors discovered diamond as something worth putting their money into and so started the investment market and soon prices began to rise in leaps and bounds. Everyone wanted graded stones and certified diamonds and diamond reports appeared all over the place, with the result that the grading in some of the labs became less and less consistent.
Dangers for the trade
Bodies such as CIBJO saw the danger in this for the trade and tried to introduce some sort of control. They did this recognizing only a certain number of laboratories, the general rule being one per country and preferably recognized by national associations. They too introduced a system of grading diamonds using terms such as ‘white’ and ‘tinted’ as explained above. They had their own set of Master Stones for color grading. It was known that they had been co-operating with the GIA but it was unclear as to how the Master Stones had been obtained. The system they adopted was to give a chart linking their stones to the GIA system, thus ‘exceptional white +’ was D, ‘rare white’ a G and so on.
The main laboratory in Antwerp was the HRD and they too had evolved their own system again using descriptive terms such as ‘white’ with their own sets of master stones. They became the main laboratory in Antwerp serving the diamond industry there through the International Diamond Council (IDC).
Thus in the mid-eighties we had several acceptable systems in operation and the diamond trade, through the encouragement of groups such as the Diamond Trading Company, thought that all those systems should be harmonized. In this way the now international diamond trade would become truly international with all countries speaking the same language in grading diamonds.
ISO Standard drafted
The main groups got together and decided to draw up an ISO Standard. These groups were the GIA, IDC, CIBJO and Scan DN. The standard was to be drafted in two parts, Part 1 to deal with Terminology and Classification. This defined how terms such as those referring to the type of inclusions within a diamond should be used and the color grades, as well as defining different shapes of diamonds. This was ISO/FDIS 11211-1. Part 2 would deal with Test Methods, explaining under what conditions color should be determined, how various measurements would be made and how these would be shown on a report. The points here are of course more numerous than I am stating in this article, but the combined papers should enable a laboratory to grade and produce a report on a diamond and all those using the Standard would produce more or less identical reports.
It was around the time of completion of Part 1 that one of the main participants decided to drop out. This was the GIA. As one who was not involved with the actual working group it is difficult to know exactly why this occurred. Maybe the GIA, considering themselves leaders in the field of diamond grading could see no point in giving their system away to be used by everyone as it was possible that many laboratories using GIA terminology would not necessarily grade to their standards.
Importance of cut
This left Scan DN, CIBJO and IDC in the working group. As I have often said in these articles there is far more in determining the price of a diamond than merely color and clarity. In considering the 4 Cs—carat, clarity, color and cut—most people forget about the cut and it is this that gives the stone its beauty. All grading reports indicate the size of the table and the depth of a stone as a percentage of its width or diameter, but it takes an expert to interpret this.
The IDC indicates the depths of the crown and the pavilion separately and then gives a comment on the proportions of the stones using terms such as ‘good’, ‘very good’ and ‘unusual’. The GIA does not give these comments on proportion but makes general judgments on the symmetry of a stone. This difference led to a compromise being reached two years ago that a proportion comment would be optional.
When the papers were finally published and circulated the IDC claimed that they had understood that proportion comment would be mandatory on all grading reports.
If the IDC wishes are accepted then there are those who feel that the GIA system would fall short of the Standard in that they do not comment on proportion. There are also those countries who have used the GIA system over the years and would not like to see s Standard that somewhat denigrates the system they have used for years and could confuse their public. At the time of writing the vote has not been completed so the result is awaited with interest.
The International Standards Organization (ISO) papers on diamond grading harmonization have at last been published and been sent to the participating countries to be voted on.
If the vote is passed it means that the world will have an ISO standard for grading diamonds. If it is not passed, then the working group will have to reconvene and it is doubtful if another paper will be published in the near future. It has taken over fifteen years to have reached this stage. Some of those who were involved in the writing of these papers have indicated they will vote against it. How has this state of affairs arisen and how will it affect diamond grading and the diamond trade and all those involved in selling grading certificates with their stones?
Terms for color
Diamonds have been graded for many years for color and clarity. Initially descriptive terms for color, sometimes based on geographical locations, were used. For example, we had ‘white’, ‘tinted’, ‘cape’, ‘wesselton’, ‘river’, ‘light brown’ stones and so on. There was usually local understanding of these terms and how they would be used, but there were no universal agreements. So partners in a firm, local dealers belonging to a diamond bourse or those traveling to, say, South Africa, would understand what a ‘cape series’ was, but this was very much an esoteric language. ‘White’ meant different things to different dealers, and one could rarely buy on the seller’s description only, one had to see the stone. The prominent systems to be used were the ones used in South Africa as a producing country, and consisted of terms ‘wesselton, ‘crystal’, and ‘cape’, with words such as ‘top’ added as a prefix. End users adopted and modified such systems and the above terminology was incorporated into the Scan D N grading system.
A further system was introduced top make the language less esoteric and terms such as ‘white’, ‘tinted’, and ‘brown’ were used with prefixes such as ‘exceptional’, ‘rare’, ‘slightly’ and ‘top’ being used. As an aside, stones sold as ‘blue white’ and ‘premier’ are now referred to as those that have fluorescence.
GIA system
In all its confusion an attempt was made by the GIA to introduce a grading system which was more objective than the subjective methods used. They picked on a certain number of stones of different shades, graded these by comparing them to each other ranging from the purest white (or, more accurately, colorlessness) to shades of pale yellow, gave letters to these stones and referred to them as ‘Master Stones’. They called the highest grade a D color, and graded the rest down using E, F, G and so on. There was a perceivable shade of color between adjacent stones in this series. Thus, a stone which looked more colorless than a G but less colorless than an F, was referred to as an F color.
The letter D was taken to be the best color and this was done, according to the late Richard Liddicoat (for many years Chairman of the GIA), to void confusion with letters already in use such as A, B and C. The systems using these letters had been further modified by using A+, A++, AA, AAA, and so on. D was the failure grade in American schools and as an ‘in joke’ and, on the assumption that D had never been used to denote a color grade, they made this the top color. The trade and public found this to a far less confusing system—they knew the lower the letter the lower was the color.
Clarity terms
On the clarity grading terms such as ‘loupe clean’, ‘very very small inclusions’ (VVS), ‘very small inclusions’ (VS), ‘small inclusions’ (SI), were used and these too were easy to understand. With such a system in place investors discovered diamond as something worth putting their money into and so started the investment market and soon prices began to rise in leaps and bounds. Everyone wanted graded stones and certified diamonds and diamond reports appeared all over the place, with the result that the grading in some of the labs became less and less consistent.
Dangers for the trade
Bodies such as CIBJO saw the danger in this for the trade and tried to introduce some sort of control. They did this recognizing only a certain number of laboratories, the general rule being one per country and preferably recognized by national associations. They too introduced a system of grading diamonds using terms such as ‘white’ and ‘tinted’ as explained above. They had their own set of Master Stones for color grading. It was known that they had been co-operating with the GIA but it was unclear as to how the Master Stones had been obtained. The system they adopted was to give a chart linking their stones to the GIA system, thus ‘exceptional white +’ was D, ‘rare white’ a G and so on.
The main laboratory in Antwerp was the HRD and they too had evolved their own system again using descriptive terms such as ‘white’ with their own sets of master stones. They became the main laboratory in Antwerp serving the diamond industry there through the International Diamond Council (IDC).
Thus in the mid-eighties we had several acceptable systems in operation and the diamond trade, through the encouragement of groups such as the Diamond Trading Company, thought that all those systems should be harmonized. In this way the now international diamond trade would become truly international with all countries speaking the same language in grading diamonds.
ISO Standard drafted
The main groups got together and decided to draw up an ISO Standard. These groups were the GIA, IDC, CIBJO and Scan DN. The standard was to be drafted in two parts, Part 1 to deal with Terminology and Classification. This defined how terms such as those referring to the type of inclusions within a diamond should be used and the color grades, as well as defining different shapes of diamonds. This was ISO/FDIS 11211-1. Part 2 would deal with Test Methods, explaining under what conditions color should be determined, how various measurements would be made and how these would be shown on a report. The points here are of course more numerous than I am stating in this article, but the combined papers should enable a laboratory to grade and produce a report on a diamond and all those using the Standard would produce more or less identical reports.
It was around the time of completion of Part 1 that one of the main participants decided to drop out. This was the GIA. As one who was not involved with the actual working group it is difficult to know exactly why this occurred. Maybe the GIA, considering themselves leaders in the field of diamond grading could see no point in giving their system away to be used by everyone as it was possible that many laboratories using GIA terminology would not necessarily grade to their standards.
Importance of cut
This left Scan DN, CIBJO and IDC in the working group. As I have often said in these articles there is far more in determining the price of a diamond than merely color and clarity. In considering the 4 Cs—carat, clarity, color and cut—most people forget about the cut and it is this that gives the stone its beauty. All grading reports indicate the size of the table and the depth of a stone as a percentage of its width or diameter, but it takes an expert to interpret this.
The IDC indicates the depths of the crown and the pavilion separately and then gives a comment on the proportions of the stones using terms such as ‘good’, ‘very good’ and ‘unusual’. The GIA does not give these comments on proportion but makes general judgments on the symmetry of a stone. This difference led to a compromise being reached two years ago that a proportion comment would be optional.
When the papers were finally published and circulated the IDC claimed that they had understood that proportion comment would be mandatory on all grading reports.
If the IDC wishes are accepted then there are those who feel that the GIA system would fall short of the Standard in that they do not comment on proportion. There are also those countries who have used the GIA system over the years and would not like to see s Standard that somewhat denigrates the system they have used for years and could confuse their public. At the time of writing the vote has not been completed so the result is awaited with interest.
Wednesday, May 02, 2007
Red And Green Labradorite Feldspar From Congo
The red and green colors in labradorites from Congo are due to copper and the differences in color are due to the presence of tiny copper colloids of different size. On the market, the red and green stones from Congo have been offered as red andesine.
A Treatment Study Of Brazilian Garnets
(via The Journal of Gemmology, Vol 29, No.4, October 2004) Sigrid G Eeckhout, Antonio C S Sabioni and Ana Claudia M Ferreira writes:
Over the past decade, there has been noticeable growth in interest in colored stones worldwide, which has led to an increase in gem exploration, production and marketing. Since garnet displays a very large variety of colors, it deserves further attention. Although reports on enhanced gemstones are widespread in the gemological literature, very few studies have been performed on the enhancements of garnets. We report the first systematic, scientific treatment study on Brazilian garnets from known geological localities, including thermal and diffusion treatment. Iron-containing species become opaque and producer ‘silvery skin’. Light yellow grossular turns to orange similar to that of imperial topaz. Other garnet varieties have stable colors, confirming the absence of color centers. A preliminary diffusion treatment of some rough grossular has produced attractive green and orange stones. Since orange gemstones are becoming increasingly popular and since the diffusion treated green grossulars resemble some emeralds in color, they may be of economic importance in the future if quantities are confirmed to justify commercial mining.
Over the past decade, there has been noticeable growth in interest in colored stones worldwide, which has led to an increase in gem exploration, production and marketing. Since garnet displays a very large variety of colors, it deserves further attention. Although reports on enhanced gemstones are widespread in the gemological literature, very few studies have been performed on the enhancements of garnets. We report the first systematic, scientific treatment study on Brazilian garnets from known geological localities, including thermal and diffusion treatment. Iron-containing species become opaque and producer ‘silvery skin’. Light yellow grossular turns to orange similar to that of imperial topaz. Other garnet varieties have stable colors, confirming the absence of color centers. A preliminary diffusion treatment of some rough grossular has produced attractive green and orange stones. Since orange gemstones are becoming increasingly popular and since the diffusion treated green grossulars resemble some emeralds in color, they may be of economic importance in the future if quantities are confirmed to justify commercial mining.
Treated Stones—Retailers In The Front Line
(via Gem & Jewellery News, Vol.7, No.1, December 1997) Harry Levy writes:
The ulcer that has been plaguing our trade has flared yet again. You will recall the recent story about the jeweler in the United States who sold filled diamonds without declaring the process to his customers. That story ended tragedy with the jeweler in question taking his own life. One must emphasize that the filling of diamonds is one of the few treatments that is recognized by all sections of the trade to be declarable.
Another case has now occurred in the USA, this time over the fissure filling of an emerald and again the retail purchaser was reportedly not told of the treatment. It is difficult to work out exactly what has happened in this case as the reports one reads in the trade press do not tell the same story. Briefly, as I understand it, an emerald was sold for $14000 and has ended up costing the seller nearly $400000 in compensation and fines.
The case occurred in Washington DC. An emerald ring was sold, and after several months was taken to a jeweler for some alterations and the emerald was damaged in the process. The jeweler informed the owner that the emerald had been filled with Opticon resin and heating had caused the damage. The original sellers claimed that the emerald they sold had not been so treated and if Opticon was now present it had not been put there by them and must have been introduced into the stone after they had sold it.
The owner sued the seller and others including the appraiser (the valuer) and the insurance company. The case was heard in front of a jury and in spite of trade testimony as to the present ambiguity about disclosure of resin filling of emeralds in the trade, the jury found in favor of the owner. The jeweler was found guilty on a number of counts including Breach of Warranties, Unlawful Trade Practice and Outrageous Trade Practice. The consumer was awarded treble damages in the amount of $78000 and, with legal costs, the total amounted to $400000. At the time of writing an appeal against judgments has been lodged.
Total disclosure?
Those who have advocated ‘total disclosure’ over the years can now say ‘We told you so’. Disclose everything and sleep at nights.
Unfortunately it is not that simple, as I have tried to point out in previous articles, because it is often difficult to detect some treatments. Stones have been treated from the time that they were first used as ornaments and objects of value. Oiling, waxing, bleaching, heating and burning are all treatments, and even cutting and polishing can be considered a treatment. And when one cuts and polishes for example an emerald, oil is used and if the stone has open fissures some of this oil will penetrate the stone.
When the trade began to organize itself through bodies such as CIBJO and the Diamond Bourses, they tried to lay down guidelines as to what treatments should be disclosed. Some treatments had long been applied to certain stones and those early legislators introduced the concept of ‘accepted trade practice.’ As new processes come about the trade initially tries to slot them in to the existing rules and if it cannot do this then new rules were made.
They try to use commonsense and look at other trades. They too have their ‘accepted trade practices.’ When you buy an article made of real leather you are not told that it has been treated, oiled, stained, stretched and has had other things done to it. Or when you buy a woolen article again the various treatments it has undergone are not enumerated.
Perhaps we should regard our trade as being sui generic, i.e. it is unique of its kind and cannot be compared to other trades. In this modern age, when consumer rights have become paramount, the trade should no longer hide behind ‘accepted trade practices’ and should tell the consumer everything they know. But this is where the problems start. The only person who knows for certain if a treatment has been applied to a stone is the person who actually carries out that treatment. If he does not disclose, or someone in the chain does not disclose, then to detect the disclosure becomes detective work and not everyone is capable of carrying out such detection.
Repeated oiling
Let us look at the specific case of the fissure filling of emeralds—this after all is one of the problems still not solved within the trade. Emeralds, from the time they are taken out of the ground, are constantly oiled. They are oiled after the rough has been cleaned, they are oiled while the rough remains unsold, they are oiled after cutting, they are oiled after polishing. In the way everyone knows that leather is oiled, dealers and jewelers have assumed that everyone knows emeralds are oiled. Like leather the oil dries out, but in contrast to leather the consumer expects the emerald to retain its beauty. Emeralds are oiled because they have open fissures (only rarely are emeralds free from open fissures) and any oil that goes in will eventually come again, as is the case with leather.
Over the past few years attempts have been made to keep the oil thus introduced in the emerald for as long as possible. This has been tried using different oils, and also pressure is used in some cases to ensure that the oil penetrates further into the stone and will thus evaporate more slowly. Attempts have also been made to seal the oil in the emerald. In recent years resins are being used, especially ones with refractive indices similar to natural emerald to make them less visible. The most popular resin that was eventually used was a synthetic one marketed under the name Opticon. This was already being used in the building trade to cover the cracks and fissures in marble and other decorative stones. But since this was still a volatile substance, albeit with low volatility they tried to seal it into the stone. It was found that it reacted with a hardening substance and solidified. At first this was done with all Opticon when it was introduced into the emerald. When it dried it solidified, but in some stones it contracted and gaps appeared inside the stone which gave rise to a rainbow effect and made the appearance worse than the untreated stones. Some fillings also discolored in time, again spoiling the appearance of the stone. Some techniques involved introduction of the resin under pressure causing the stone to be in tension and liable to shatter if any pressure was applied.
Hardening substance
To overcome these problems the Opticon was introduced into the stone and the hardening substance was applied to the surface only. Thus the theory was that this would seal in the filler without incurring the problems encountered above. But again it was found that tension could remain in the stone rendering it more fragile than untreated stones. So in many cases now the Opticon is introduced into the stone in the way that oil was used in the old days without the use of any hardening material. The trade does not like to use the word Opticon, as this is a trade name and other similar resins may be used. So the term now used is resin filled and the resin may be natural or artificial, i.e. man-made.
The traditionalists wanted to differentiate between oils that they had used and the new resins now being used. It is difficult to find a rationale for such thoughts. Perhaps they wished to protect their old stocks, perhaps they were scared of change, but there was a clamor within the trade, but not by the public, to differentiate between oils and resins. Many more gem quality stones can have their appearance improved with resins than with traditional oils, which was perhaps the reason for a sudden increase in the number of such stones on the market.
Raman spectroscopy
The situation at present is that many people in the trade regard the fissure filling of an emerald with a resin to be inferior to that of an oil and refuse to buy resin-filled stones. The demand was made on the laboratories to make this differentiation, and most labs claimed they could do so. But then came the claim by some laboratories that with the use of Raman spectroscope they could now positively identify the filling materials. Such a claim implies that without the use of such a instrument, the detection of the filler to be a resin as opposed to an oil was, in many cases, more guesswork than knowledge.
How does the Raman spectroscope work? In Rapaport Diamond Report (20 (38)) it is made clear that even the use of this latest technology is not foolproof. Briefly a laser beam of light is pointed at the filler and the resulting spectra are compared with those of known substances. A stone may undergo several treatments with different substances and the Raman analysis will only give a result for the one spot on which the beam has been focused, which is minute. So, many spots would have to be examined to give a more complete answer. Such an instrument costs about $200000 so many laboratories cannot afford such an expense.
What is the answer?
Where does the answer lie to such a problem? The trade is beginning to realize the answer should come through education and not merely legislation. The education must be effective in the High Street shops, for it is the retailer who is in the front line. And it is the sales person who is obliged in law to sell correctly described goods—which means to a certain extent educating the customer.
Many dealers now feel that filling a stone with a resin is no different to filling a stone with an oil. If a hardener is used the situation is of course different. Information is transmitted down the line by the use of general disclosure that stones have fissures filled to improve their clarity and others, such as corundum, are heated to improve their color and sometimes clarity. This is the best that the trade has come up with at present.
How will all this stand up in a court here? I am no lawyer but I suspect that the judge will listen to the trade practice if the dispute is within the trade, but may apply other standards if a member of the general public claims that they have been cheated.
The ulcer that has been plaguing our trade has flared yet again. You will recall the recent story about the jeweler in the United States who sold filled diamonds without declaring the process to his customers. That story ended tragedy with the jeweler in question taking his own life. One must emphasize that the filling of diamonds is one of the few treatments that is recognized by all sections of the trade to be declarable.
Another case has now occurred in the USA, this time over the fissure filling of an emerald and again the retail purchaser was reportedly not told of the treatment. It is difficult to work out exactly what has happened in this case as the reports one reads in the trade press do not tell the same story. Briefly, as I understand it, an emerald was sold for $14000 and has ended up costing the seller nearly $400000 in compensation and fines.
The case occurred in Washington DC. An emerald ring was sold, and after several months was taken to a jeweler for some alterations and the emerald was damaged in the process. The jeweler informed the owner that the emerald had been filled with Opticon resin and heating had caused the damage. The original sellers claimed that the emerald they sold had not been so treated and if Opticon was now present it had not been put there by them and must have been introduced into the stone after they had sold it.
The owner sued the seller and others including the appraiser (the valuer) and the insurance company. The case was heard in front of a jury and in spite of trade testimony as to the present ambiguity about disclosure of resin filling of emeralds in the trade, the jury found in favor of the owner. The jeweler was found guilty on a number of counts including Breach of Warranties, Unlawful Trade Practice and Outrageous Trade Practice. The consumer was awarded treble damages in the amount of $78000 and, with legal costs, the total amounted to $400000. At the time of writing an appeal against judgments has been lodged.
Total disclosure?
Those who have advocated ‘total disclosure’ over the years can now say ‘We told you so’. Disclose everything and sleep at nights.
Unfortunately it is not that simple, as I have tried to point out in previous articles, because it is often difficult to detect some treatments. Stones have been treated from the time that they were first used as ornaments and objects of value. Oiling, waxing, bleaching, heating and burning are all treatments, and even cutting and polishing can be considered a treatment. And when one cuts and polishes for example an emerald, oil is used and if the stone has open fissures some of this oil will penetrate the stone.
When the trade began to organize itself through bodies such as CIBJO and the Diamond Bourses, they tried to lay down guidelines as to what treatments should be disclosed. Some treatments had long been applied to certain stones and those early legislators introduced the concept of ‘accepted trade practice.’ As new processes come about the trade initially tries to slot them in to the existing rules and if it cannot do this then new rules were made.
They try to use commonsense and look at other trades. They too have their ‘accepted trade practices.’ When you buy an article made of real leather you are not told that it has been treated, oiled, stained, stretched and has had other things done to it. Or when you buy a woolen article again the various treatments it has undergone are not enumerated.
Perhaps we should regard our trade as being sui generic, i.e. it is unique of its kind and cannot be compared to other trades. In this modern age, when consumer rights have become paramount, the trade should no longer hide behind ‘accepted trade practices’ and should tell the consumer everything they know. But this is where the problems start. The only person who knows for certain if a treatment has been applied to a stone is the person who actually carries out that treatment. If he does not disclose, or someone in the chain does not disclose, then to detect the disclosure becomes detective work and not everyone is capable of carrying out such detection.
Repeated oiling
Let us look at the specific case of the fissure filling of emeralds—this after all is one of the problems still not solved within the trade. Emeralds, from the time they are taken out of the ground, are constantly oiled. They are oiled after the rough has been cleaned, they are oiled while the rough remains unsold, they are oiled after cutting, they are oiled after polishing. In the way everyone knows that leather is oiled, dealers and jewelers have assumed that everyone knows emeralds are oiled. Like leather the oil dries out, but in contrast to leather the consumer expects the emerald to retain its beauty. Emeralds are oiled because they have open fissures (only rarely are emeralds free from open fissures) and any oil that goes in will eventually come again, as is the case with leather.
Over the past few years attempts have been made to keep the oil thus introduced in the emerald for as long as possible. This has been tried using different oils, and also pressure is used in some cases to ensure that the oil penetrates further into the stone and will thus evaporate more slowly. Attempts have also been made to seal the oil in the emerald. In recent years resins are being used, especially ones with refractive indices similar to natural emerald to make them less visible. The most popular resin that was eventually used was a synthetic one marketed under the name Opticon. This was already being used in the building trade to cover the cracks and fissures in marble and other decorative stones. But since this was still a volatile substance, albeit with low volatility they tried to seal it into the stone. It was found that it reacted with a hardening substance and solidified. At first this was done with all Opticon when it was introduced into the emerald. When it dried it solidified, but in some stones it contracted and gaps appeared inside the stone which gave rise to a rainbow effect and made the appearance worse than the untreated stones. Some fillings also discolored in time, again spoiling the appearance of the stone. Some techniques involved introduction of the resin under pressure causing the stone to be in tension and liable to shatter if any pressure was applied.
Hardening substance
To overcome these problems the Opticon was introduced into the stone and the hardening substance was applied to the surface only. Thus the theory was that this would seal in the filler without incurring the problems encountered above. But again it was found that tension could remain in the stone rendering it more fragile than untreated stones. So in many cases now the Opticon is introduced into the stone in the way that oil was used in the old days without the use of any hardening material. The trade does not like to use the word Opticon, as this is a trade name and other similar resins may be used. So the term now used is resin filled and the resin may be natural or artificial, i.e. man-made.
The traditionalists wanted to differentiate between oils that they had used and the new resins now being used. It is difficult to find a rationale for such thoughts. Perhaps they wished to protect their old stocks, perhaps they were scared of change, but there was a clamor within the trade, but not by the public, to differentiate between oils and resins. Many more gem quality stones can have their appearance improved with resins than with traditional oils, which was perhaps the reason for a sudden increase in the number of such stones on the market.
Raman spectroscopy
The situation at present is that many people in the trade regard the fissure filling of an emerald with a resin to be inferior to that of an oil and refuse to buy resin-filled stones. The demand was made on the laboratories to make this differentiation, and most labs claimed they could do so. But then came the claim by some laboratories that with the use of Raman spectroscope they could now positively identify the filling materials. Such a claim implies that without the use of such a instrument, the detection of the filler to be a resin as opposed to an oil was, in many cases, more guesswork than knowledge.
How does the Raman spectroscope work? In Rapaport Diamond Report (20 (38)) it is made clear that even the use of this latest technology is not foolproof. Briefly a laser beam of light is pointed at the filler and the resulting spectra are compared with those of known substances. A stone may undergo several treatments with different substances and the Raman analysis will only give a result for the one spot on which the beam has been focused, which is minute. So, many spots would have to be examined to give a more complete answer. Such an instrument costs about $200000 so many laboratories cannot afford such an expense.
What is the answer?
Where does the answer lie to such a problem? The trade is beginning to realize the answer should come through education and not merely legislation. The education must be effective in the High Street shops, for it is the retailer who is in the front line. And it is the sales person who is obliged in law to sell correctly described goods—which means to a certain extent educating the customer.
Many dealers now feel that filling a stone with a resin is no different to filling a stone with an oil. If a hardener is used the situation is of course different. Information is transmitted down the line by the use of general disclosure that stones have fissures filled to improve their clarity and others, such as corundum, are heated to improve their color and sometimes clarity. This is the best that the trade has come up with at present.
How will all this stand up in a court here? I am no lawyer but I suspect that the judge will listen to the trade practice if the dispute is within the trade, but may apply other standards if a member of the general public claims that they have been cheated.
Hot Gems And Fake Diamonds
(via Gem & Jewellery News, Vol. 7, Number 2, March 1998) Harry Levy writes:
1998 started with an international alarm for the gem trade and jewelry markets. The scare began in Bangkok with news that quantities of radioactive chrysoberyl cat’s eyes were being sold there and exported all over the world.
A few gem species have been irradiated for a number of years now to improve or change their color. The stone most subjected to this treatment has been white topaz. The most common types of irradiation have been electron and neutron bombardment of the stones to produce various shades of blue.
Electron irradiation produces paler shades of blue, known in the trade as ‘sky blue’. In this instance rough or cut pieces of white topaz are exposed to electron irradiation and the longer the exposure the stronger is the color, but a saturation point is reached beyond which the color will not intensify. When the stones are annealed (heated and maintained at certain temperatures) they turn blue. On cooling the stones maintain their color and the color change is permanent as far as we know.
The dealer or cutter who has the stones irradiated determines the amount of radiation the stones should be exposed to; this is an economic decision, as the longer the stones are irradiated the higher is the cost charged by the laboratory. Different stones from different localities need different quantities of irradiation to obtain the optimum color, but the dealer cannot experiment with small quantities as the fee for irradiation is based on the time and strength of exposure for material in a chamber of fixed capacity, however full it is. The other popular method is to expose the stones to neutron irradiation and in this instance the blue color produced is known in the trade as ‘London blue’. The color known as ‘Swiss blue’ is obtained by applying both types of irradiation to the topazes.
Since the color changes produced in topaz have been so dramatic, other stones have been exposed to such treatments in the hope of producing similar changes and this has resulted in such stones as ‘hot pink’ tourmalines (the hotness referring to the color not the radioactivity), and various colors in diamonds.
Subjecting a stone to irradiation is not something that can be done in the back of a kitchen or in a shed at the bottom of the garden. Stones are irradiated in a nuclear accelerator at known nuclear plants, research institutions or universities. Normally they are subject to the most rigorous government controls and workers would never release material which was dangerously radioactive to anyone involved in the gem trade. The stones are only released from such establishments when they display acceptable levels of radioactivity.
Scares about radioactive gemstones have been circulating ever since it became known that they could be treated in this manner. We are all exposed to various levels of irradiation in our everyday lives. During one of the early discussions it was alleged that a single flight in Concorde exposed one to more radiation, due to the height of the flight path, than being covered in irradiated topaz for a lifetime.
Other scare stories have concerned irradiated topaz being stolen from various vaults in Brazil, where they had been put to cool, and sold on the international markets while they were still dangerously radioactive. A similar story emerged at one of the Hong Kong shows about such stones from China. The basis for such stories seems to be economic, where dealers from one center are more than keen to believe that stones coming cheaper from another source must be dangerous.
Dealers and others who handle such stones would never expose themselves, their families, their staff or their customers to such danger, although with rumors constantly circulating in the trade an increasing number of dealers are beginning to include an instrument for detecting radioactivity as part of their equipment. A simple Geiger counter registers most but not all the known rays that could be present, other instruments are needed to register the troublesome ones.
Coming back to our radioactive chysoberyls, the media picked up the story and television pictures were flashed round the world showing worried-looking dealers and jewelry shop owners in Bangkok being shown such stones next to ticking Geiger counters. This is a marvelous story for an investigative reporter and whole television programmes on this topic have been shown in such countries as Germany.
Unless the trade is very careful, a lay person watch such a programme will be told about radioactive chrysoberyl cat’s eyes, but will only remember radioactivity in association with gemstones in general, and continued media coverage will soon convince him and his ilk that every stone and every diamond is radioactive and hence all jewelry is dangerous to wear.
Of course, the public has rarely proved itself to be so fickle. They are aware that many things they come into contact with have been subjected to irradiation, but they trust the authorities and the traders to be responsible and not subject them to any danger. It again comes down to education and all those involved in the jewelry trade must make themselves aware of exactly what they are handling. It is not enough to have the ability to buy and sell something at a profit, because the trade should be the ones most able to educate the public, who are their customers, answer their questions and allay any fears they may come across. And the safest way to trade is to deal with reputable suppliers.
1998 started with an international alarm for the gem trade and jewelry markets. The scare began in Bangkok with news that quantities of radioactive chrysoberyl cat’s eyes were being sold there and exported all over the world.
A few gem species have been irradiated for a number of years now to improve or change their color. The stone most subjected to this treatment has been white topaz. The most common types of irradiation have been electron and neutron bombardment of the stones to produce various shades of blue.
Electron irradiation produces paler shades of blue, known in the trade as ‘sky blue’. In this instance rough or cut pieces of white topaz are exposed to electron irradiation and the longer the exposure the stronger is the color, but a saturation point is reached beyond which the color will not intensify. When the stones are annealed (heated and maintained at certain temperatures) they turn blue. On cooling the stones maintain their color and the color change is permanent as far as we know.
The dealer or cutter who has the stones irradiated determines the amount of radiation the stones should be exposed to; this is an economic decision, as the longer the stones are irradiated the higher is the cost charged by the laboratory. Different stones from different localities need different quantities of irradiation to obtain the optimum color, but the dealer cannot experiment with small quantities as the fee for irradiation is based on the time and strength of exposure for material in a chamber of fixed capacity, however full it is. The other popular method is to expose the stones to neutron irradiation and in this instance the blue color produced is known in the trade as ‘London blue’. The color known as ‘Swiss blue’ is obtained by applying both types of irradiation to the topazes.
Since the color changes produced in topaz have been so dramatic, other stones have been exposed to such treatments in the hope of producing similar changes and this has resulted in such stones as ‘hot pink’ tourmalines (the hotness referring to the color not the radioactivity), and various colors in diamonds.
Subjecting a stone to irradiation is not something that can be done in the back of a kitchen or in a shed at the bottom of the garden. Stones are irradiated in a nuclear accelerator at known nuclear plants, research institutions or universities. Normally they are subject to the most rigorous government controls and workers would never release material which was dangerously radioactive to anyone involved in the gem trade. The stones are only released from such establishments when they display acceptable levels of radioactivity.
Scares about radioactive gemstones have been circulating ever since it became known that they could be treated in this manner. We are all exposed to various levels of irradiation in our everyday lives. During one of the early discussions it was alleged that a single flight in Concorde exposed one to more radiation, due to the height of the flight path, than being covered in irradiated topaz for a lifetime.
Other scare stories have concerned irradiated topaz being stolen from various vaults in Brazil, where they had been put to cool, and sold on the international markets while they were still dangerously radioactive. A similar story emerged at one of the Hong Kong shows about such stones from China. The basis for such stories seems to be economic, where dealers from one center are more than keen to believe that stones coming cheaper from another source must be dangerous.
Dealers and others who handle such stones would never expose themselves, their families, their staff or their customers to such danger, although with rumors constantly circulating in the trade an increasing number of dealers are beginning to include an instrument for detecting radioactivity as part of their equipment. A simple Geiger counter registers most but not all the known rays that could be present, other instruments are needed to register the troublesome ones.
Coming back to our radioactive chysoberyls, the media picked up the story and television pictures were flashed round the world showing worried-looking dealers and jewelry shop owners in Bangkok being shown such stones next to ticking Geiger counters. This is a marvelous story for an investigative reporter and whole television programmes on this topic have been shown in such countries as Germany.
Unless the trade is very careful, a lay person watch such a programme will be told about radioactive chrysoberyl cat’s eyes, but will only remember radioactivity in association with gemstones in general, and continued media coverage will soon convince him and his ilk that every stone and every diamond is radioactive and hence all jewelry is dangerous to wear.
Of course, the public has rarely proved itself to be so fickle. They are aware that many things they come into contact with have been subjected to irradiation, but they trust the authorities and the traders to be responsible and not subject them to any danger. It again comes down to education and all those involved in the jewelry trade must make themselves aware of exactly what they are handling. It is not enough to have the ability to buy and sell something at a profit, because the trade should be the ones most able to educate the public, who are their customers, answer their questions and allay any fears they may come across. And the safest way to trade is to deal with reputable suppliers.
How Can The Independent Jeweller Compete?
(via Gems & Jewellery News, Vol. 8, Number 1, December 1998) Harry Levy writes:
By the time you read this article the Christmas season will be behind us. At the time of writing it is difficult to predict what sort of Christmas our trade will have this year. The patterns of yesteryear have long since left us. In those days, by the end of October most outlets had placed their orders for Christmas and, apart from a few specials at the last minute, we all knew what sort of year we would have. As far as the independent jeweler is concerned today, most of his sales will consist of specials, and he will leave his orders up to the last minute, as will his customers.
So rather than sit and take stock as to what has happened this year let us try to look to the future, to next year and beyond.
Alternative outlets
The jewelry trade has fragmented and the loser has been the traditional high street jewelry shop. He has seen his business go to the multinationals, mail order catalogues, and now mail order shops, TV outlets and soon the Internet, although this is with us already, as well as the auction houses. How much business these new outlets have actually taken away, as opposed to creating new demands and bringing in different sections of the public to buy jewelry items is debatable.
I recall many years ago when I first set up home, I needed some fitted carpets. I had a cousin in the trade who promised me that he would supply me the carpets. I bought from him and it was only several weeks later, when I was in one of the specialist carpet stores with branches everywhere, that I saw my identical carpet at prices above twenty percent below what I had paid my cousin. On complaining to him, he informed me that the groups had a much higher buying power than him and thus could negotiate better prices than he could get.
We have a similar situation in our trade at present. Many jewelers have remarked that they cannot make an article for the price that the same thing can be bought from these outlets. How can they compete?
The simple answer is that they cannot. So in order to survive they must concentrate on selling articles which the outlets cannot make. Put very simply, it means that they must try to sell jewelry which cannot be readily duplicated.
Mass production
The mass market depends on selling numbers of identical units. A piece of jewelry is selected by a buyer or a panel to go into their range. In almost all cases the buyers are not jewelry specialists and in order to ensure that they get and sell pieces that match up to their original samples, they insist on each item being exactly the same for any given line. Thus, if one is selling an amethyst and diamond cluster ring, the diamonds must all be of a similar size and quality and the amethysts, likewise, must all be identical. It is not enough that they be of the same size and shape, but must all be of the same hue in color and purity.
The manufacturer who supplies these articles must set up to produce identical units and periodically to reduce his prices in order to stay in with the buying group. He can do this by improving his manufacturing processes and reducing the price of his components, as well as reducing his profits.
Falling standards
Several years ago, one of the manufacturers who were supplying one of the multiples stopped buying a type of stone for which he had given me regular orders. When I asked him why he had stopped ordering these stones from me and accused him of buying them elsewhere, he remarked that the group was constantly asking him to reduce his price. The article was a pair of earrings, and the only way left for him to reduce the price was to make the gold thinner and thinner, until he reached the situation where there was not enough gold to hold the stones in place so they kept dropping out. In the end he dropped the line.
The manufacturers in this country try to source their components, and eventually find that the article can be produced and purchased much more cheaply abroad. Finally they become importers and put the finishing touches in this country as part of their manufacturing process. With the prospect of hallmarking being no longer mandatory in this country, they will become merely re-packers of such items. They also run the risk that their customers, in turn, will use outlets abroad and cut them out totally. Luckily for us, many of these items produced abroad do not have the quality of those that are made in this country and hopefully the buyers will appreciate this fact and return to rely on home produced goods.
I see little future for those of us who are middle people in our trade. The large groups will find ways of marketing the goods to the public, and sourcing them, cutting out our retailers and manufacturers. Their main criterion will be price and while it remains that way quality will suffer.
The way forward
Quality is the factor on which our own trade will survive, producing jewelry that is good in quality and value for money. Such jewelry must be sold on the rarity of its components and the craftsmanship of its makers. There will always be a place for the High Street Jeweler, even if he has to move into a mall and be right next to his competitors, provided he can sell things which are not easily imitated.
I come across many young and new designers and they are all finding outlets for the unique pieces of jewelry they produce. The mass of cheap jewelry available now is making the public more aware of jewelry: they buy these items to wear a few times and then throw away. Let us hope that this awareness they are getting will make them want something a little better and more lasting for that special occasion, and when they think of buying such an item they will come into a high street jeweler.
I hope you all have an enjoyable Christmas and that some of you will put pen to paper and let us have your views about our trade. It is going through a state of flux, both in marketing, as the movement of goods becomes easier and in the amount and variety of treatments of the natural and synthetic gems that go into the making of a piece of jewelry.
By the time you read this article the Christmas season will be behind us. At the time of writing it is difficult to predict what sort of Christmas our trade will have this year. The patterns of yesteryear have long since left us. In those days, by the end of October most outlets had placed their orders for Christmas and, apart from a few specials at the last minute, we all knew what sort of year we would have. As far as the independent jeweler is concerned today, most of his sales will consist of specials, and he will leave his orders up to the last minute, as will his customers.
So rather than sit and take stock as to what has happened this year let us try to look to the future, to next year and beyond.
Alternative outlets
The jewelry trade has fragmented and the loser has been the traditional high street jewelry shop. He has seen his business go to the multinationals, mail order catalogues, and now mail order shops, TV outlets and soon the Internet, although this is with us already, as well as the auction houses. How much business these new outlets have actually taken away, as opposed to creating new demands and bringing in different sections of the public to buy jewelry items is debatable.
I recall many years ago when I first set up home, I needed some fitted carpets. I had a cousin in the trade who promised me that he would supply me the carpets. I bought from him and it was only several weeks later, when I was in one of the specialist carpet stores with branches everywhere, that I saw my identical carpet at prices above twenty percent below what I had paid my cousin. On complaining to him, he informed me that the groups had a much higher buying power than him and thus could negotiate better prices than he could get.
We have a similar situation in our trade at present. Many jewelers have remarked that they cannot make an article for the price that the same thing can be bought from these outlets. How can they compete?
The simple answer is that they cannot. So in order to survive they must concentrate on selling articles which the outlets cannot make. Put very simply, it means that they must try to sell jewelry which cannot be readily duplicated.
Mass production
The mass market depends on selling numbers of identical units. A piece of jewelry is selected by a buyer or a panel to go into their range. In almost all cases the buyers are not jewelry specialists and in order to ensure that they get and sell pieces that match up to their original samples, they insist on each item being exactly the same for any given line. Thus, if one is selling an amethyst and diamond cluster ring, the diamonds must all be of a similar size and quality and the amethysts, likewise, must all be identical. It is not enough that they be of the same size and shape, but must all be of the same hue in color and purity.
The manufacturer who supplies these articles must set up to produce identical units and periodically to reduce his prices in order to stay in with the buying group. He can do this by improving his manufacturing processes and reducing the price of his components, as well as reducing his profits.
Falling standards
Several years ago, one of the manufacturers who were supplying one of the multiples stopped buying a type of stone for which he had given me regular orders. When I asked him why he had stopped ordering these stones from me and accused him of buying them elsewhere, he remarked that the group was constantly asking him to reduce his price. The article was a pair of earrings, and the only way left for him to reduce the price was to make the gold thinner and thinner, until he reached the situation where there was not enough gold to hold the stones in place so they kept dropping out. In the end he dropped the line.
The manufacturers in this country try to source their components, and eventually find that the article can be produced and purchased much more cheaply abroad. Finally they become importers and put the finishing touches in this country as part of their manufacturing process. With the prospect of hallmarking being no longer mandatory in this country, they will become merely re-packers of such items. They also run the risk that their customers, in turn, will use outlets abroad and cut them out totally. Luckily for us, many of these items produced abroad do not have the quality of those that are made in this country and hopefully the buyers will appreciate this fact and return to rely on home produced goods.
I see little future for those of us who are middle people in our trade. The large groups will find ways of marketing the goods to the public, and sourcing them, cutting out our retailers and manufacturers. Their main criterion will be price and while it remains that way quality will suffer.
The way forward
Quality is the factor on which our own trade will survive, producing jewelry that is good in quality and value for money. Such jewelry must be sold on the rarity of its components and the craftsmanship of its makers. There will always be a place for the High Street Jeweler, even if he has to move into a mall and be right next to his competitors, provided he can sell things which are not easily imitated.
I come across many young and new designers and they are all finding outlets for the unique pieces of jewelry they produce. The mass of cheap jewelry available now is making the public more aware of jewelry: they buy these items to wear a few times and then throw away. Let us hope that this awareness they are getting will make them want something a little better and more lasting for that special occasion, and when they think of buying such an item they will come into a high street jeweler.
I hope you all have an enjoyable Christmas and that some of you will put pen to paper and let us have your views about our trade. It is going through a state of flux, both in marketing, as the movement of goods becomes easier and in the amount and variety of treatments of the natural and synthetic gems that go into the making of a piece of jewelry.
Monday, April 30, 2007
The Tourist Trap Debate
(via Gem Market News, Jan/Feb 2007, Vol 26, Issue 1) Richard B Drucker, GG writes:
Every year, tourists purchase jewelry from port town shops, major city tourist areas, and even from cruise ships, either on board or at a recommended local store. The vacation is a great memory until they return home, only to be told by a local jeweler or appraiser that they have been ripped off. Are they really a victim of a devious tourist trap, or has the local jeweler or appraiser low-balled the value in an attempt to make a sale themselves or discredit the tourist industry?
The truth is that when tourists leave their home country, they are definitely at a disadvantage when shopping for any item, not just jewelry. Tourist stores know that they are dealing with clients with discretionary income and impulsive spending behavior when away from home. If they have a change of heart for any reason when they get home, exchanges or refunds are unlikely due to the difficulty related to the distance. There might be guarantees but once home, the guarantees may be hard to invoke. Since cruise lines often get commissions from jewelry stores they recommend, they may be helpful in assisting the passenger in a dispute. Credit card companies historically helped out and are good advice for tourists to use, however, they too, are becoming reluctant to help out because there are so many claims and few are warranted.
When there is a dispute, the consumer will probably be directed to get an independent appraisal and that is one reason that Gemworld sees so many of these purchases. In fairness to the tourist stores and cruise ships, we do see many cases where the purchase price is legitimate, so this is not just about the tourist trap.
Most of the time, when a client comes to us for the independent appraisal thinking they are overpaid, we substantiate the price paid. The problem starts when the jeweler says they overpaid and their store could sell it for less. Although they could sell it for less, this may also be an unfair statement. There are different markets to buy jewelry in and different markets have different pricing. Some markets get higher markups due to overhead, location, advertising, and yes, even the fact that they may be giving commissions to cruise operators. Someone can always sell something for less, but that is not what is at issue. The only thing that is important is whether the tourist received what they expected at a fair price for the location in which they made the purchase.
Appraising in the Appropriate Market
Appraising in the appropriate market means research and due diligence by the appraiser. It means finding out what similar items sell for in similar stores. In the Sept/Oct 2006 issue of GMN, an article on markets appeared by Joseph Tenhagen. In it he identifies 14 separate and stratified markets in which jewelry can be purchased. It is our opinion that the appraiser should identify the market and research prices accordingly. We always ask where an item was purchased and value accordingly.
Occasionally, there may be reason to appraise an item in a different market than the one in which it was purchased. In the tourist examples, one may use the argument that if the item were lost, it would not be replaced in the same market. Appraisers may ask the question, “Where would you most likely replace this item if it were lost?” Since the tourist is unlikely to hop aboard the plane and return to the place of purchase, nor would the insurance company go to that store either, could it be appraised for a lower value in a different market? The answer is maybe.
First, if it is trademarked or branded from that store or location, it may likely have to be replaced only by that store. Then, you could not transfer the appraisal to a generic local replacement center. The opportunity to use a different market for replacement comes from the fact that most replacement type insurance policies state that they have the right to replace at their cost or to settle for the price that they could actually buy the item for, then one would argue that a low value is always appropriate. However, this will be the case with most purchases from all retail markets, and I am not sure that is where appraising should go. No jeweler would ever make a fair profit if this started to happen.
Sometimes a discussion may ensue regarding replacement and the client may request a lower value for insurance. Without going into a full discussion here about the appraisal methodology and valuation science, I will simply say that if a lower value is used for any reason, that reason should be clearly stated on the appraisal report. Something such as this could be added: Client purchased item at XYZ Jewelers, St.Thomas, for $4000.00. Although a fair price for that location, replacement value here in local markets has been determined to be $3200.00 and that value is being used at the request of the client.
Now, I know that appraisers love to debate methodology and appraising. There are many that would disagree with the above statement and procedure. One subscriber/appraiser recently emailed us regarding problems with a Caribbean purchase. While the heart of the issue was in some false claims, we also discussed valuation methods. He wrote the following. “My position is that it really doesn’t matter what the seller or buyer think the appraisal value of any item should be. It is what the market says it is. The client and/or seller can have absolutely no influence on an ethical appraisal. And, as an appraiser, I can’t really have an opinion on whether the price paid was too high or too low. There is no mention in the purpose and function statements of the appraisal being intended as a purchase price justification. As such, there is really no reason to identify the purchase price or to justify either the seller’s or the buyer’s position in a transaction. As appraisers, we are not in the business of taking sides (not should we be).”
While there is truth to much of this, other issues are at hand here. His position is that nothing influences what he ultimately appraises an item for. He states that the market dictates price, but what market? Market activity dictates value. Market location is an important factor in examining this activity. Disparaging terms such as rip off, etc., should be avoided. Appraisers are no more immune from civil recourse stemming from interfering in the commerce of others than anyone else. A purchase price is a valid indicator of value. If a comparable can be purchased in a different market for less, this might be noted. However, do not allow this to suggest that the original price was an unfair price for the market the consumer chose to shop within.
Appraisals of jewelry purchased in tourist markets present a challenge in that the appraiser must reconcile the role of market influence on value. Often these assignments blend two distinct tasks. One is assigning an insurance replacement value to aid the client in obtaining insurance. In this case, the purchase price may not be a significant consideration because the issue becomes not what was paid, but what would be paid to make the client whole again in case of a loss. However, this should not be done in a way that dismisses the legitimacy of an established tourist market.
Another example clearly illustrates this with real estate. Suppose a real estate appraiser were appraising a house. The appraiser finds that the builder of the home has built this exact home in a different city in another part of the country and it sold there for a lower price. The appraiser uses this price stating that this is all it would cost to replace the home with this builder. While the materials may be the same, the market value varies with location. The house does not cost the same in all locations, yet the appraiser would never say to the client that they were ripped off by paying the higher price in the place in which they chose to buy.
When the Gloves Come off
While we have defended many cases as the independent arbitrator, these cases have strictly involved the question of price. A bigger problem in our opinion is the misinformation and use of reports that inflate the grading of gems being sold. The value may be OK for what is sold or it may be high. In both cases, we will not defend the sale.
Every year, tourists purchase jewelry from port town shops, major city tourist areas, and even from cruise ships, either on board or at a recommended local store. The vacation is a great memory until they return home, only to be told by a local jeweler or appraiser that they have been ripped off. Are they really a victim of a devious tourist trap, or has the local jeweler or appraiser low-balled the value in an attempt to make a sale themselves or discredit the tourist industry?
The truth is that when tourists leave their home country, they are definitely at a disadvantage when shopping for any item, not just jewelry. Tourist stores know that they are dealing with clients with discretionary income and impulsive spending behavior when away from home. If they have a change of heart for any reason when they get home, exchanges or refunds are unlikely due to the difficulty related to the distance. There might be guarantees but once home, the guarantees may be hard to invoke. Since cruise lines often get commissions from jewelry stores they recommend, they may be helpful in assisting the passenger in a dispute. Credit card companies historically helped out and are good advice for tourists to use, however, they too, are becoming reluctant to help out because there are so many claims and few are warranted.
When there is a dispute, the consumer will probably be directed to get an independent appraisal and that is one reason that Gemworld sees so many of these purchases. In fairness to the tourist stores and cruise ships, we do see many cases where the purchase price is legitimate, so this is not just about the tourist trap.
Most of the time, when a client comes to us for the independent appraisal thinking they are overpaid, we substantiate the price paid. The problem starts when the jeweler says they overpaid and their store could sell it for less. Although they could sell it for less, this may also be an unfair statement. There are different markets to buy jewelry in and different markets have different pricing. Some markets get higher markups due to overhead, location, advertising, and yes, even the fact that they may be giving commissions to cruise operators. Someone can always sell something for less, but that is not what is at issue. The only thing that is important is whether the tourist received what they expected at a fair price for the location in which they made the purchase.
Appraising in the Appropriate Market
Appraising in the appropriate market means research and due diligence by the appraiser. It means finding out what similar items sell for in similar stores. In the Sept/Oct 2006 issue of GMN, an article on markets appeared by Joseph Tenhagen. In it he identifies 14 separate and stratified markets in which jewelry can be purchased. It is our opinion that the appraiser should identify the market and research prices accordingly. We always ask where an item was purchased and value accordingly.
Occasionally, there may be reason to appraise an item in a different market than the one in which it was purchased. In the tourist examples, one may use the argument that if the item were lost, it would not be replaced in the same market. Appraisers may ask the question, “Where would you most likely replace this item if it were lost?” Since the tourist is unlikely to hop aboard the plane and return to the place of purchase, nor would the insurance company go to that store either, could it be appraised for a lower value in a different market? The answer is maybe.
First, if it is trademarked or branded from that store or location, it may likely have to be replaced only by that store. Then, you could not transfer the appraisal to a generic local replacement center. The opportunity to use a different market for replacement comes from the fact that most replacement type insurance policies state that they have the right to replace at their cost or to settle for the price that they could actually buy the item for, then one would argue that a low value is always appropriate. However, this will be the case with most purchases from all retail markets, and I am not sure that is where appraising should go. No jeweler would ever make a fair profit if this started to happen.
Sometimes a discussion may ensue regarding replacement and the client may request a lower value for insurance. Without going into a full discussion here about the appraisal methodology and valuation science, I will simply say that if a lower value is used for any reason, that reason should be clearly stated on the appraisal report. Something such as this could be added: Client purchased item at XYZ Jewelers, St.Thomas, for $4000.00. Although a fair price for that location, replacement value here in local markets has been determined to be $3200.00 and that value is being used at the request of the client.
Now, I know that appraisers love to debate methodology and appraising. There are many that would disagree with the above statement and procedure. One subscriber/appraiser recently emailed us regarding problems with a Caribbean purchase. While the heart of the issue was in some false claims, we also discussed valuation methods. He wrote the following. “My position is that it really doesn’t matter what the seller or buyer think the appraisal value of any item should be. It is what the market says it is. The client and/or seller can have absolutely no influence on an ethical appraisal. And, as an appraiser, I can’t really have an opinion on whether the price paid was too high or too low. There is no mention in the purpose and function statements of the appraisal being intended as a purchase price justification. As such, there is really no reason to identify the purchase price or to justify either the seller’s or the buyer’s position in a transaction. As appraisers, we are not in the business of taking sides (not should we be).”
While there is truth to much of this, other issues are at hand here. His position is that nothing influences what he ultimately appraises an item for. He states that the market dictates price, but what market? Market activity dictates value. Market location is an important factor in examining this activity. Disparaging terms such as rip off, etc., should be avoided. Appraisers are no more immune from civil recourse stemming from interfering in the commerce of others than anyone else. A purchase price is a valid indicator of value. If a comparable can be purchased in a different market for less, this might be noted. However, do not allow this to suggest that the original price was an unfair price for the market the consumer chose to shop within.
Appraisals of jewelry purchased in tourist markets present a challenge in that the appraiser must reconcile the role of market influence on value. Often these assignments blend two distinct tasks. One is assigning an insurance replacement value to aid the client in obtaining insurance. In this case, the purchase price may not be a significant consideration because the issue becomes not what was paid, but what would be paid to make the client whole again in case of a loss. However, this should not be done in a way that dismisses the legitimacy of an established tourist market.
Another example clearly illustrates this with real estate. Suppose a real estate appraiser were appraising a house. The appraiser finds that the builder of the home has built this exact home in a different city in another part of the country and it sold there for a lower price. The appraiser uses this price stating that this is all it would cost to replace the home with this builder. While the materials may be the same, the market value varies with location. The house does not cost the same in all locations, yet the appraiser would never say to the client that they were ripped off by paying the higher price in the place in which they chose to buy.
When the Gloves Come off
While we have defended many cases as the independent arbitrator, these cases have strictly involved the question of price. A bigger problem in our opinion is the misinformation and use of reports that inflate the grading of gems being sold. The value may be OK for what is sold or it may be high. In both cases, we will not defend the sale.
Origin Determination Of Rubies, Sapphires And Emeralds
The lecture was delivered on the 8th December, 2004 at AIGS by Dietmar Schwarz and Christian Dunaigre, Gubelin Gem Lab, Switzerland.
In brief:
Historical data: The concept of country of origin determination started 60+ years ago in Switzerland by Dr. Eduard Gubelin who did methodical studies on internal features of gemstones originating from important gem localities around the world. During 1950s and 1970s the number of important gem deposits were restricted due to political and economic reasons. Some of the major deposits include:
Ruby: Ratnapura/Elahera in Sri Lanka
Mogok Stone Tract / Mong Hshu / Namya in Burma
Trat province in Thailand
Magari / Umba valley in East Africa
Different localities in Vietnam
Different localities in Madagascar
Sapphires: Ratnapura / Elahera in Sri Lanka
Mogok Stone Tract in Burma
Kanchanaburi / Chantaburi in Thailand
Different localities in Australia
Different localities in Madagascar
Different localities in the USA
Emeralds: Muzo / Chivor in Colombia
Different localities in Zambia
Sandawana in Zimbabwe
Ural mountains in Russia
Different localities in Brazil
Different localities in Afghanistan
Different localities in Pakistan
In today’s gem market, traders like to submit a ruby, sapphire or emerald for origin determination due to its high value. Inclusions do affect prices. There are number of reasons why inclusions alone are unreliable for determining the origin of gemstones. The current gemological knowledge of inclusions for various ruby + sapphire + emerald + other important colored stone occurrences are incomplete. Study of inclusions is a relatively new science and there is so much that remains to be learned + so many inclusions that have yet to be identified and catalogued. The key areas to be studied are:
- variation of the inclusion parameters within samples from a given locality
- similarity of inclusion populations in samples from different localities
- what sort of diagnostic origin information can we collect from a cut gemstone
- limitations in the determination of origin
- chemical fingerprinting
- advanced instruments such as UV, VIS-NIR, FTIR, Raman +++
During the 80s and 90s many new gem deposits were discovered. It was found that the mineralogical-gemological properties of the new sources were quite similar or even identical to those observed from the traditional sources. For instance blue sapphires from Madagascar displayed features that resembled sapphires from Sri Lanka, East Africa, Burma or even Kashmir. At the same time gemstones even when found in similar geological environments still showed some locality-specific features which allowed a clear separation from gems originating from a deposit of the same generic type such rubies from the Mogok and Mong Hshu.
Today gemological laboratories dealing with origin determination of colored stones are confronted with the gem production of an increasing number of mining areas all over the world. Some of the traditional sources are not producing gems consistently. Without any doubt the island of Madagascar has enormous potential for almost all gemstone species located in different regions of the country and related to different types of host rocks. Advanced + proprietary treatment techniques in rubies, sapphires and emerald may result in the elimination of characteristic features and make origin determination more difficult.
In brief:
Historical data: The concept of country of origin determination started 60+ years ago in Switzerland by Dr. Eduard Gubelin who did methodical studies on internal features of gemstones originating from important gem localities around the world. During 1950s and 1970s the number of important gem deposits were restricted due to political and economic reasons. Some of the major deposits include:
Ruby: Ratnapura/Elahera in Sri Lanka
Mogok Stone Tract / Mong Hshu / Namya in Burma
Trat province in Thailand
Magari / Umba valley in East Africa
Different localities in Vietnam
Different localities in Madagascar
Sapphires: Ratnapura / Elahera in Sri Lanka
Mogok Stone Tract in Burma
Kanchanaburi / Chantaburi in Thailand
Different localities in Australia
Different localities in Madagascar
Different localities in the USA
Emeralds: Muzo / Chivor in Colombia
Different localities in Zambia
Sandawana in Zimbabwe
Ural mountains in Russia
Different localities in Brazil
Different localities in Afghanistan
Different localities in Pakistan
In today’s gem market, traders like to submit a ruby, sapphire or emerald for origin determination due to its high value. Inclusions do affect prices. There are number of reasons why inclusions alone are unreliable for determining the origin of gemstones. The current gemological knowledge of inclusions for various ruby + sapphire + emerald + other important colored stone occurrences are incomplete. Study of inclusions is a relatively new science and there is so much that remains to be learned + so many inclusions that have yet to be identified and catalogued. The key areas to be studied are:
- variation of the inclusion parameters within samples from a given locality
- similarity of inclusion populations in samples from different localities
- what sort of diagnostic origin information can we collect from a cut gemstone
- limitations in the determination of origin
- chemical fingerprinting
- advanced instruments such as UV, VIS-NIR, FTIR, Raman +++
During the 80s and 90s many new gem deposits were discovered. It was found that the mineralogical-gemological properties of the new sources were quite similar or even identical to those observed from the traditional sources. For instance blue sapphires from Madagascar displayed features that resembled sapphires from Sri Lanka, East Africa, Burma or even Kashmir. At the same time gemstones even when found in similar geological environments still showed some locality-specific features which allowed a clear separation from gems originating from a deposit of the same generic type such rubies from the Mogok and Mong Hshu.
Today gemological laboratories dealing with origin determination of colored stones are confronted with the gem production of an increasing number of mining areas all over the world. Some of the traditional sources are not producing gems consistently. Without any doubt the island of Madagascar has enormous potential for almost all gemstone species located in different regions of the country and related to different types of host rocks. Advanced + proprietary treatment techniques in rubies, sapphires and emerald may result in the elimination of characteristic features and make origin determination more difficult.
Friday, April 27, 2007
Kashmir sapphire
On April 25, Christies auction house also set a record for the highest per carat price ever paid for a cushion cut 22.66 carat Kashmir sapphire, which was sold to an anonymous buyer for $3.064 million.
Useful link:
www.christies.com
Useful link:
www.christies.com
Baroda Pearls
Christies auction house sold a two strand natural pearl necklace with matching earrings, brooch and ring to a private Asian buyer for $7.096 million. The necklace features 68 of the finest and largest pearls from the seven strand natural pearl necklace that once belonged to The Royal Treasury of the Maharaja of Baroda.
Useful link:
www.christies.com
Useful link:
www.christies.com
Sapphire With Yellowish Orange Surface Coating
(via ICA Early Warning Flash, No.46, August 16, 1991) GIA GTL writes:
Description
The stone is a transparent oval mixed cut weighing 0.98 carat and measuring 6.80x4.90x3.36mm. It is medium yellowish orange in color which to the unaided eye appears uniform in distribution.
Gemological properties
Standard gemological testing identify the stone as a natural corundum. It exhibits no distinct absorption features when examined with a desk-model spectroscope and is inert to both long and short wave ultraviolet radiation. Interestingly, it exhibits no pleochroism when viewed through a calcite dichroscope, something that would be expected in a corundum of this hue and depth of color.
Magnification
Diffused transmitted lighting reveals that the stone has been surface coated. Irregularities in the coating—scratches and pits on pavilion facets as well as abrasions on facet junctions---indicate that this is an essentially colorless stone. Examination in surface reflected lighting reveals a predominantly purple iridescence on pavilion facets.
Additional testing
The ultraviolet visible absorption spectrum was found to be similar to that of natural color yellow sapphire with features related to Fe3+. A qualitative chemical analysis performed by EDXRF reveals the presence of iron as the dominating trace element, with small amounts of potassium, calcium, titanium and gallium. Neither ultraviolet visible absorption spectroscopy nor X-ray fluorescence helped to detect or characterize the coating.
Discussion
The microscope features of this stone show it to have been coated, with the coating being responsible for both the apparent body color and superficial iridescence. It is important to note that this is a surface coating and not a diffusion treatment.
‘Aqua Aura’ is the trade name used for a type of coated gem seen for some time now. This consists of such materials as unfashioned rock crystal specimen as well as faceted rock crystal and colorless topaz to which a thin layer of gold has been applied. The treatment produces a greenish blue apparent body color (the transmission color of the gold coating) and superficial iridescence. Treated gems of these type exhibit microscopic features like those described above. It is possible that the corundum described herein has been subjected to a similar coating but of a different substance.
Description
The stone is a transparent oval mixed cut weighing 0.98 carat and measuring 6.80x4.90x3.36mm. It is medium yellowish orange in color which to the unaided eye appears uniform in distribution.
Gemological properties
Standard gemological testing identify the stone as a natural corundum. It exhibits no distinct absorption features when examined with a desk-model spectroscope and is inert to both long and short wave ultraviolet radiation. Interestingly, it exhibits no pleochroism when viewed through a calcite dichroscope, something that would be expected in a corundum of this hue and depth of color.
Magnification
Diffused transmitted lighting reveals that the stone has been surface coated. Irregularities in the coating—scratches and pits on pavilion facets as well as abrasions on facet junctions---indicate that this is an essentially colorless stone. Examination in surface reflected lighting reveals a predominantly purple iridescence on pavilion facets.
Additional testing
The ultraviolet visible absorption spectrum was found to be similar to that of natural color yellow sapphire with features related to Fe3+. A qualitative chemical analysis performed by EDXRF reveals the presence of iron as the dominating trace element, with small amounts of potassium, calcium, titanium and gallium. Neither ultraviolet visible absorption spectroscopy nor X-ray fluorescence helped to detect or characterize the coating.
Discussion
The microscope features of this stone show it to have been coated, with the coating being responsible for both the apparent body color and superficial iridescence. It is important to note that this is a surface coating and not a diffusion treatment.
‘Aqua Aura’ is the trade name used for a type of coated gem seen for some time now. This consists of such materials as unfashioned rock crystal specimen as well as faceted rock crystal and colorless topaz to which a thin layer of gold has been applied. The treatment produces a greenish blue apparent body color (the transmission color of the gold coating) and superficial iridescence. Treated gems of these type exhibit microscopic features like those described above. It is possible that the corundum described herein has been subjected to a similar coating but of a different substance.
Wednesday, April 25, 2007
Dyed Natural Corundum As A Ruby Imitation
(via ICA Early Warning Flash, No.50, December 11, 1991) SSEF writes:
The following observations were made in the SSEF laboratory and further during examination of stones by Dr K Schmetzer and Mr F J Schupp, Germany.
Submitted stone chains and faceted stones were consisting of a heavily fractured type of natural corundum material, probably stained during quench cracking. They were sold as originating from India. The flattened beads were up to 15mm in diameter, the faceted oval stones between 5 and 8 carats.
Closer examination under the microscope reveals that the red color is deposited on irregular fracture planes only. The material is colored by a violetish red stain, the result of an artificial fracture treatment. The color is similar to the color of somewhat dark ruby and makes a convincing ruby imitation.
The stones show natural inclusions which consist of sets of parallel twin lamellae in one or two directions, forming straight intersection lines. Boehmite particles are confined to these intersection lines. Small double refractive mineral inclusions forming clusters were also observed. Stones with similar properties are known by us to come from East Africa. In immersion, light yellow or greenish yellow portions are forming areas between the fractures, showing the original color of the material. The red color is only seen in fractures. In thick pieces, the artificial treatment (i.e the stained fractures) is more difficult to see.
Beside of the above, the treated material can be recognized by a yellow fluorescence under long wave UV radiation. The red artificial color is said to fade after exposure of some weeks to daylight. Also the rather uneven color distribution on the fractures, as seen under magnification, is diagnostic.
The chromophore element of ruby is chromium. The easiest way to prove its presence in corundum is by observing the absorption spectrum with a pocket spectroscope. Chromium causes a prominent set of absorption lines and a fluorescence doublet in the red part of the spectrum. These characteristics are not visible in the dyed corundum since they lack chromium and therefore are not ruby.
The following observations were made in the SSEF laboratory and further during examination of stones by Dr K Schmetzer and Mr F J Schupp, Germany.
Submitted stone chains and faceted stones were consisting of a heavily fractured type of natural corundum material, probably stained during quench cracking. They were sold as originating from India. The flattened beads were up to 15mm in diameter, the faceted oval stones between 5 and 8 carats.
Closer examination under the microscope reveals that the red color is deposited on irregular fracture planes only. The material is colored by a violetish red stain, the result of an artificial fracture treatment. The color is similar to the color of somewhat dark ruby and makes a convincing ruby imitation.
The stones show natural inclusions which consist of sets of parallel twin lamellae in one or two directions, forming straight intersection lines. Boehmite particles are confined to these intersection lines. Small double refractive mineral inclusions forming clusters were also observed. Stones with similar properties are known by us to come from East Africa. In immersion, light yellow or greenish yellow portions are forming areas between the fractures, showing the original color of the material. The red color is only seen in fractures. In thick pieces, the artificial treatment (i.e the stained fractures) is more difficult to see.
Beside of the above, the treated material can be recognized by a yellow fluorescence under long wave UV radiation. The red artificial color is said to fade after exposure of some weeks to daylight. Also the rather uneven color distribution on the fractures, as seen under magnification, is diagnostic.
The chromophore element of ruby is chromium. The easiest way to prove its presence in corundum is by observing the absorption spectrum with a pocket spectroscope. Chromium causes a prominent set of absorption lines and a fluorescence doublet in the red part of the spectrum. These characteristics are not visible in the dyed corundum since they lack chromium and therefore are not ruby.
Vietnamese Ruby Salted With Synthetic Ruby
(via ICA Early Warning Flash, no.22, March 27, 1992) Grahame Brown writes:
Background
Following the discovery of alluvial ruby in Vietnam in the late 80s, small parcels of distinctively colored purplish pink to purplish red rough, as well as some cut stones, became available for purchase in Australia in early 1990. Initially the major sellers of this ruby appeared to be Vietnamese residents of Australia. Subsequently, Australian gem merchants purchased parcels of Vietnamese ruby, in Bangkok, for resale in Australia.
Over the last year I have been requested to examine several parcels of Vietnamese ruby rough, as well as some small parcels of faceted Vietnamese ruby, to establish the natural origin of this ruby. This alert has been issued in response to my findings.
Observed features
The rough examined appeared to be water worn, and sometimes displayed visually convincing evidence of external crystal forms, and parting planes. The few unabraded fracture surfaces and parting planes on the surface of this rough allowed very limited visual access to its interior.
Suspicious were immediately raised when some of the rubies, faceted from allegedly Vietnamese ruby rough, displayed:
- diffused curved color banding
- curving empty surface reaching fractures
- profiled gas bubbles and closely associated whitish granular masses
Of these inclusions, the curved color banding was most difficult to detect. Visibility of this curved color banding was enhanced when the immersed ruby was rotated in diffused transmitted light generated from a laterally directed fibre optic wand.
As diffused curved color banding and curving surface reaching fractures characterize heat treated Verneuil synthetic ruby, and profiled bubbles and whitish granular partly melted alumina powder are not uncommonly found in the sintered area of attachment between the Verneuil boule and the ceramic pedestal of the chalumeau……a hypothesis that some parcels of Vietnamese ruby rough were being salted with rough shaped, tumbled, heat treated Verneuil synthetic ruby seems possible.
As some of these inclusions were also observed in small parcels of faceted Vietnamese ruby, buyers of this new exciting should exercise caution.
Background
Following the discovery of alluvial ruby in Vietnam in the late 80s, small parcels of distinctively colored purplish pink to purplish red rough, as well as some cut stones, became available for purchase in Australia in early 1990. Initially the major sellers of this ruby appeared to be Vietnamese residents of Australia. Subsequently, Australian gem merchants purchased parcels of Vietnamese ruby, in Bangkok, for resale in Australia.
Over the last year I have been requested to examine several parcels of Vietnamese ruby rough, as well as some small parcels of faceted Vietnamese ruby, to establish the natural origin of this ruby. This alert has been issued in response to my findings.
Observed features
The rough examined appeared to be water worn, and sometimes displayed visually convincing evidence of external crystal forms, and parting planes. The few unabraded fracture surfaces and parting planes on the surface of this rough allowed very limited visual access to its interior.
Suspicious were immediately raised when some of the rubies, faceted from allegedly Vietnamese ruby rough, displayed:
- diffused curved color banding
- curving empty surface reaching fractures
- profiled gas bubbles and closely associated whitish granular masses
Of these inclusions, the curved color banding was most difficult to detect. Visibility of this curved color banding was enhanced when the immersed ruby was rotated in diffused transmitted light generated from a laterally directed fibre optic wand.
As diffused curved color banding and curving surface reaching fractures characterize heat treated Verneuil synthetic ruby, and profiled bubbles and whitish granular partly melted alumina powder are not uncommonly found in the sintered area of attachment between the Verneuil boule and the ceramic pedestal of the chalumeau……a hypothesis that some parcels of Vietnamese ruby rough were being salted with rough shaped, tumbled, heat treated Verneuil synthetic ruby seems possible.
As some of these inclusions were also observed in small parcels of faceted Vietnamese ruby, buyers of this new exciting should exercise caution.
Blue Diffusion Treated Synthetic Sapphires
(via ICA Early Warning Flash, No.55, June 2, 1992) GIA GTL writes:
Background
Recently the GIA Gem Trade Laboratory, Inc facilities in both Santa Monica, California, and New York, received for identification parcels of faceted stones that were determined to have been diffusion-treated to produce a blue coloration. In one instance, gemological investigation revealed that all three treated stones were synthetic sapphires. In a second instance, a parcel of about 40 stones was determined to consist of approximately 2/3 natural corundums and 1/3 synthetic corundums.
Visible observations/magnification
Examination using immersion with diffused transmitted illumination revealed features characteristic of stone color enhanced through diffusion treatment; for a summary of diagnostic properties, see ‘The Identification of Blue Diffusion Treated Sapphires’ (Kane et al) in the summer 1990 issue of Gems & Gemology.
Using magnification and darkfield illumination it was possible to detect the presence of various inclusions in a number of the stones that identified these hosts as being of natural origin. In other specimens, the presence of gas bubbles proved the hosts to be synthetic. Some stones, however, exhibited no diagnostic features through microscopic examination.
Plato test
The Plato test was also used in the determination of natural vs synthetic origin. A positive Plato test, further substantiating synthetic origin, was obtained with most of the stones identified as synthetic by virtue of diagnostic inclusions, as well as with those specimens without any such internal features. It should be noted, however, that characteristic positive Plato test appearance was generally more subtle than what we are accustomed to seeing.
Ultraviolet luminescence
Examination under both long and short wave ultraviolet radiation revealed some additional potentially useful information. In many cases, the diffusion treated stones exhibited some small areas where there was no blue diffused color, most likely due to this having been removed in repolishing after diffusion treatment. Under long wave UV radiation, these areas on a number of the blue diffusion treated natural sapphires fluoresced reddish orange, a reaction often associated with colorless to light blue corundum from Sri Lanka. When exposed to short wave UV, these same areas fluoresced a chalky whitish blue, a reaction associated with some sapphires that have been exposed to high temperature treatments.
The synthetic sapphires, however, were are all completely inert to long wave UV radiation, including areas where the blue diffusion treated coloration was absent; these areas fluoresced a chalky whitish blue to short wave UV. Such luminescent reactions may be exhibited by colorless synthetic sapphires. While the short wave reactions of both natural and synthetic sapphires were similar in these cases, the effect was slightly stronger with the synthetic samples. It should be noted, however, that the strength of fluorescent reactions in natural, synthetic, and treated sapphires can vary considerably.
Discussion
Immersion used in conjunction with diffused, transmitted illumination is generally quite effective in detecting the presence of diffusion treated color in corundum. Detecting this enhancement, however, does not prove or even indicate whether the treated gem material is of natural or synthetic origin. In the above examples, a combination of magnification and Plato test were used to make this determination.
Ultraviolet luminescence provided some additional, potentially useful information. In this regard, it should be noted that the presence of the reddish orange long wave reaction may be considered a good indication that the starting material is natural; although the absence of such a reaction indicates neither natural nor synthetic origin.
Background
Recently the GIA Gem Trade Laboratory, Inc facilities in both Santa Monica, California, and New York, received for identification parcels of faceted stones that were determined to have been diffusion-treated to produce a blue coloration. In one instance, gemological investigation revealed that all three treated stones were synthetic sapphires. In a second instance, a parcel of about 40 stones was determined to consist of approximately 2/3 natural corundums and 1/3 synthetic corundums.
Visible observations/magnification
Examination using immersion with diffused transmitted illumination revealed features characteristic of stone color enhanced through diffusion treatment; for a summary of diagnostic properties, see ‘The Identification of Blue Diffusion Treated Sapphires’ (Kane et al) in the summer 1990 issue of Gems & Gemology.
Using magnification and darkfield illumination it was possible to detect the presence of various inclusions in a number of the stones that identified these hosts as being of natural origin. In other specimens, the presence of gas bubbles proved the hosts to be synthetic. Some stones, however, exhibited no diagnostic features through microscopic examination.
Plato test
The Plato test was also used in the determination of natural vs synthetic origin. A positive Plato test, further substantiating synthetic origin, was obtained with most of the stones identified as synthetic by virtue of diagnostic inclusions, as well as with those specimens without any such internal features. It should be noted, however, that characteristic positive Plato test appearance was generally more subtle than what we are accustomed to seeing.
Ultraviolet luminescence
Examination under both long and short wave ultraviolet radiation revealed some additional potentially useful information. In many cases, the diffusion treated stones exhibited some small areas where there was no blue diffused color, most likely due to this having been removed in repolishing after diffusion treatment. Under long wave UV radiation, these areas on a number of the blue diffusion treated natural sapphires fluoresced reddish orange, a reaction often associated with colorless to light blue corundum from Sri Lanka. When exposed to short wave UV, these same areas fluoresced a chalky whitish blue, a reaction associated with some sapphires that have been exposed to high temperature treatments.
The synthetic sapphires, however, were are all completely inert to long wave UV radiation, including areas where the blue diffusion treated coloration was absent; these areas fluoresced a chalky whitish blue to short wave UV. Such luminescent reactions may be exhibited by colorless synthetic sapphires. While the short wave reactions of both natural and synthetic sapphires were similar in these cases, the effect was slightly stronger with the synthetic samples. It should be noted, however, that the strength of fluorescent reactions in natural, synthetic, and treated sapphires can vary considerably.
Discussion
Immersion used in conjunction with diffused, transmitted illumination is generally quite effective in detecting the presence of diffusion treated color in corundum. Detecting this enhancement, however, does not prove or even indicate whether the treated gem material is of natural or synthetic origin. In the above examples, a combination of magnification and Plato test were used to make this determination.
Ultraviolet luminescence provided some additional, potentially useful information. In this regard, it should be noted that the presence of the reddish orange long wave reaction may be considered a good indication that the starting material is natural; although the absence of such a reaction indicates neither natural nor synthetic origin.
Tuesday, April 24, 2007
Synthetic Green Quartz
(via ICA Early Warning Flash, No. 63, November 17, 1992) GIA GTL writes:
Background
At the Tucson Gem and Mineral shows in February of 1991, we noted dealers offering large quantities of synthetic quartz, reportedly of Russian origin. Among these was a transparent dark green type that visually resembles tourmaline. This green synthetic quartz was also being offered at the Tucson shows this past February; it was our impression that even more faceted material was being offered this year.
Recently, the GIA Gem Trade Laboratory, Inc in Santa Monica received for identification from two separate clients faceted specimens of what we identified as dark green synthetic quartz. In both cases, the material has been represented to our clients as a new type of natural green quartz from Brazil.
Gemological properties
Gemological testing revealed refractive indices, birefringence, and specific gravity consistent with quartz, both natural and synthetic. The specimens were inert to both long and short wave ultraviolet radiation.
Examination under immersion between crossed polaroids shows that the material was untwined, with a bulls eye optical interference figure. Under magnification we noted parallel green color banding similar to that seen in a reference sample of synthetic green quartz of Russian origin. Also noted was some angular brown color zoning that ran perpendicular to the green banding, a feature we have noted in other colors of hydrothermal synthetic quartz. One specimen also contained numerous tiny white pinpoint inclusions of undetermined origin.
Chemistry
Energy Dispersive X-ray fluorescence detected the presence of silicon, potassium, and iron. This differed only slightly from the chemistry of the synthetic green quartz reference specimen. It is believed that the iron detected is responsible for the green coloration.
Discussion
In the above cases, the client’s specimens were all identified as synthetic green quartz. It is important to note that, while green quartz does occur in nature (and is sometimes referred to as praseolite or prasiolita), such material is typically light in tone. To our knowledge, natural green quartz with this depth of color has not been reported.
Background
At the Tucson Gem and Mineral shows in February of 1991, we noted dealers offering large quantities of synthetic quartz, reportedly of Russian origin. Among these was a transparent dark green type that visually resembles tourmaline. This green synthetic quartz was also being offered at the Tucson shows this past February; it was our impression that even more faceted material was being offered this year.
Recently, the GIA Gem Trade Laboratory, Inc in Santa Monica received for identification from two separate clients faceted specimens of what we identified as dark green synthetic quartz. In both cases, the material has been represented to our clients as a new type of natural green quartz from Brazil.
Gemological properties
Gemological testing revealed refractive indices, birefringence, and specific gravity consistent with quartz, both natural and synthetic. The specimens were inert to both long and short wave ultraviolet radiation.
Examination under immersion between crossed polaroids shows that the material was untwined, with a bulls eye optical interference figure. Under magnification we noted parallel green color banding similar to that seen in a reference sample of synthetic green quartz of Russian origin. Also noted was some angular brown color zoning that ran perpendicular to the green banding, a feature we have noted in other colors of hydrothermal synthetic quartz. One specimen also contained numerous tiny white pinpoint inclusions of undetermined origin.
Chemistry
Energy Dispersive X-ray fluorescence detected the presence of silicon, potassium, and iron. This differed only slightly from the chemistry of the synthetic green quartz reference specimen. It is believed that the iron detected is responsible for the green coloration.
Discussion
In the above cases, the client’s specimens were all identified as synthetic green quartz. It is important to note that, while green quartz does occur in nature (and is sometimes referred to as praseolite or prasiolita), such material is typically light in tone. To our knowledge, natural green quartz with this depth of color has not been reported.
Synthetic Green Quartz
(via ICA Early Warning Flash, No. 63, November 17, 1992) GIA GTL writes:
Background
At the Tucson Gem and Mineral shows in February of 1991, we noted dealers offering large quantities of synthetic quartz, reportedly of Russian origin. Among these was a transparent dark green type that visually resembles tourmaline. This green synthetic quartz was also being offered at the Tucson shows this past February; it was our impression that even more faceted material was being offered this year.
Recently, the GIA Gem Trade Laboratory, Inc in Santa Monica received for identification from two separate clients faceted specimens of what we identified as dark green synthetic quartz. In both cases, the material has been represented to our clients as a new type of natural green quartz from Brazil.
Gemological properties
Gemological testing revealed refractive indices, birefringence, and specific gravity consistent with quartz, both natural and synthetic. The specimens were inert to both long and short wave ultraviolet radiation.
Examination under immersion between crossed polaroids shows that the material was untwined, with a bulls eye optical interference figure. Under magnification we noted parallel green color banding similar to that seen in a reference sample of synthetic green quartz of Russian origin. Also noted was some angular brown color zoning that ran perpendicular to the green banding, a feature we have noted in other colors of hydrothermal synthetic quartz. One specimen also contained numerous tiny white pinpoint inclusions of undetermined origin.
Chemistry
Energy Dispersive X-ray fluorescence detected the presence of silicon, potassium, and iron. This differed only slightly from the chemistry of the synthetic green quartz reference specimen. It is believed that the iron detected is responsible for the green coloration.
Discussion
In the above cases, the client’s specimens were all identified as synthetic green quartz. It is important to note that, while green quartz does occur in nature (and is sometimes referred to as praseolite or prasiolita), such material is typically light in tone. To our knowledge, natural green quartz with this depth of color has not been reported.
Background
At the Tucson Gem and Mineral shows in February of 1991, we noted dealers offering large quantities of synthetic quartz, reportedly of Russian origin. Among these was a transparent dark green type that visually resembles tourmaline. This green synthetic quartz was also being offered at the Tucson shows this past February; it was our impression that even more faceted material was being offered this year.
Recently, the GIA Gem Trade Laboratory, Inc in Santa Monica received for identification from two separate clients faceted specimens of what we identified as dark green synthetic quartz. In both cases, the material has been represented to our clients as a new type of natural green quartz from Brazil.
Gemological properties
Gemological testing revealed refractive indices, birefringence, and specific gravity consistent with quartz, both natural and synthetic. The specimens were inert to both long and short wave ultraviolet radiation.
Examination under immersion between crossed polaroids shows that the material was untwined, with a bulls eye optical interference figure. Under magnification we noted parallel green color banding similar to that seen in a reference sample of synthetic green quartz of Russian origin. Also noted was some angular brown color zoning that ran perpendicular to the green banding, a feature we have noted in other colors of hydrothermal synthetic quartz. One specimen also contained numerous tiny white pinpoint inclusions of undetermined origin.
Chemistry
Energy Dispersive X-ray fluorescence detected the presence of silicon, potassium, and iron. This differed only slightly from the chemistry of the synthetic green quartz reference specimen. It is believed that the iron detected is responsible for the green coloration.
Discussion
In the above cases, the client’s specimens were all identified as synthetic green quartz. It is important to note that, while green quartz does occur in nature (and is sometimes referred to as praseolite or prasiolita), such material is typically light in tone. To our knowledge, natural green quartz with this depth of color has not been reported.
Maxixe Type Beryls
(via ICA Early Warning Flash, No.72, July 29, 1993) Grahame Brown writes:
Preamble
Maxixe-type beryls are potentially color fading, strongly hued blue, green, blue green, yellow green, and yellow beryls that have been created by irradiation and selective heat treatment of previously pale to light colored beryl that has a very specific precursor color center.
Although the identifying features of color fading deep blue and deep green Maxixe-type beryls have been known since the early 1970s, little information has been published about the identifying features of color fading strongly hued greenish yellow to yellow green Maxixe-type beryls, or more importantly, somewhat color stable yellow Maxixe-type beryls.
While dark blue and less common dark green Maxixe-type beryls first appeared on world gem markets about 20 years ago, the recent appearance of well faceted, large size (<20 ct), eye clean, strongly hued greenish yellow, yellow green, and yellow Maxixe-type beryls may indicate renewed interest in the manufacture of these color enhanced beryls.
Identification
Irrespective of color, or whether or not the rough has or has not been oriented to display best color through the table of the faceted beryl, Maxixe-type beryls can be identified by:
An essential first step:
Using a conoscope, or equivalent gemological instrument such as a Snow Figure-O-Scope to accurately locate the optic axis (direction of single refraction or direction of the ordinary ray) in the suspect beryl.
As essential second step:
Examine the beryl, in the direction of its ordinary ray, with a hand-held dichroscope. If the beryl is a Maxixe-type, two adjacent dark color (of equal strength) will be observed. In contrast, if the beryl is a naturally colored aquamarine or heliodor, two light color (of equal strength) will be observed.
A confirmatory third step:
Examine the beryl, in the direction of its ordinary ray, with a prism or diffraction grating spectroscope. If the beryl is not examined, precisely along the direction of its ordinary ray, identifying Maxixe-type absorptions, that consist of a distinctive pattern of narrow absorptions of varying strength between 700nm (red) and 550nm (green), may not be observed.
Fade testing by exposing the suspect beryl to intense sunlight for more than a week, or by heating it for 30 minutes at 200-450 F, or by exposing it to a 100 W incandescent light bulb for 150 hours at a distance of 15cm, is an undesirable, destructive form of gem testing.
Consequently this ultimate test of fading potential is unlikely to be applied, except in the research laboratory.
However, in spite of this obvious limitation, fade testing does not provide the ultimate test for color stability. Under any of the fade testing conditions specified above:
Deep blue Maxixe-type beryls do not fade rapidly, and dramatically.
Greenish yellow to yellow green Maxixe-type beryls essentially loose their greenish component and fade to a yellowish hue.
Yellow Maxixe-type beryls loose any green component in their color, and may also fade.
Preamble
Maxixe-type beryls are potentially color fading, strongly hued blue, green, blue green, yellow green, and yellow beryls that have been created by irradiation and selective heat treatment of previously pale to light colored beryl that has a very specific precursor color center.
Although the identifying features of color fading deep blue and deep green Maxixe-type beryls have been known since the early 1970s, little information has been published about the identifying features of color fading strongly hued greenish yellow to yellow green Maxixe-type beryls, or more importantly, somewhat color stable yellow Maxixe-type beryls.
While dark blue and less common dark green Maxixe-type beryls first appeared on world gem markets about 20 years ago, the recent appearance of well faceted, large size (<20 ct), eye clean, strongly hued greenish yellow, yellow green, and yellow Maxixe-type beryls may indicate renewed interest in the manufacture of these color enhanced beryls.
Identification
Irrespective of color, or whether or not the rough has or has not been oriented to display best color through the table of the faceted beryl, Maxixe-type beryls can be identified by:
An essential first step:
Using a conoscope, or equivalent gemological instrument such as a Snow Figure-O-Scope to accurately locate the optic axis (direction of single refraction or direction of the ordinary ray) in the suspect beryl.
As essential second step:
Examine the beryl, in the direction of its ordinary ray, with a hand-held dichroscope. If the beryl is a Maxixe-type, two adjacent dark color (of equal strength) will be observed. In contrast, if the beryl is a naturally colored aquamarine or heliodor, two light color (of equal strength) will be observed.
A confirmatory third step:
Examine the beryl, in the direction of its ordinary ray, with a prism or diffraction grating spectroscope. If the beryl is not examined, precisely along the direction of its ordinary ray, identifying Maxixe-type absorptions, that consist of a distinctive pattern of narrow absorptions of varying strength between 700nm (red) and 550nm (green), may not be observed.
Fade testing by exposing the suspect beryl to intense sunlight for more than a week, or by heating it for 30 minutes at 200-450 F, or by exposing it to a 100 W incandescent light bulb for 150 hours at a distance of 15cm, is an undesirable, destructive form of gem testing.
Consequently this ultimate test of fading potential is unlikely to be applied, except in the research laboratory.
However, in spite of this obvious limitation, fade testing does not provide the ultimate test for color stability. Under any of the fade testing conditions specified above:
Deep blue Maxixe-type beryls do not fade rapidly, and dramatically.
Greenish yellow to yellow green Maxixe-type beryls essentially loose their greenish component and fade to a yellowish hue.
Yellow Maxixe-type beryls loose any green component in their color, and may also fade.
Fracture-filled Fancy Pink Diamond
(via ICA Early Warning Flash, No.65, December 21, 1992) GAGTL writes:
A pink cut-cornered square modified brilliant diamond was submitted to the Gem Testing Laboratory for the determination of the origin of its color—whether it was of natural or treated color and for the determination of the color grade.
The diamond weighed 3.35 carats and measured approx. 8.32x8.08x6.53mm. Upon examination with a 10x lens, one was struck by the many feathers visible within the stone. Viewing the diamond from various angles and by transmitted light, one could detect many surface reaching fractures displaying iridescent colors implying these were filled with air. But also noticeable were the tell-tale blue and orange flashes in some fractures indicating that these had been filled with an artificial material.
Spectroscopic investigation of the stone proved it to be a diamond of natural color and of type IaAB. The nature of the internal colored grain lines and the frosted appearance of some of the fractures indicated that the diamond may have been mined in Argyle, Australia.
If graded, the color grade would be fancy pink and the clarity grade would be pique III. However, The Gem Testing Laboratory does not issue grading reports on fracture filled diamonds. The poor clarity grade apparent subsequent to fracture treatment and the presence of untreated air-filled fractures indicate that the clarity enhancement process was not successful.
Although the Laboratory has tested fracture-filled diamonds before, this is the first instance we have seen of a fancy colored diamond being so treated.
A pink cut-cornered square modified brilliant diamond was submitted to the Gem Testing Laboratory for the determination of the origin of its color—whether it was of natural or treated color and for the determination of the color grade.
The diamond weighed 3.35 carats and measured approx. 8.32x8.08x6.53mm. Upon examination with a 10x lens, one was struck by the many feathers visible within the stone. Viewing the diamond from various angles and by transmitted light, one could detect many surface reaching fractures displaying iridescent colors implying these were filled with air. But also noticeable were the tell-tale blue and orange flashes in some fractures indicating that these had been filled with an artificial material.
Spectroscopic investigation of the stone proved it to be a diamond of natural color and of type IaAB. The nature of the internal colored grain lines and the frosted appearance of some of the fractures indicated that the diamond may have been mined in Argyle, Australia.
If graded, the color grade would be fancy pink and the clarity grade would be pique III. However, The Gem Testing Laboratory does not issue grading reports on fracture filled diamonds. The poor clarity grade apparent subsequent to fracture treatment and the presence of untreated air-filled fractures indicate that the clarity enhancement process was not successful.
Although the Laboratory has tested fracture-filled diamonds before, this is the first instance we have seen of a fancy colored diamond being so treated.
Hydrothermal Synthetic Rubies
(via ICA Early Warning Flash, No.66, January 28, 1993) GGL writes:
Background
During the Fall season of 1991, we first became aware of a production of hydrothermal synthetic rubies being made in Russia. At that time, we were informed that the production was only consisting of very small stones and therefore this seemed to be more of a scientific than commercial interest. During the next year and a half, we did not receive any additional information concerning further developments of this product. While on a recent trip to Bangkok though three samples were acquired which were reportedly from a recent production of Russian hydrothermal synthetic rubies. Seeing as how this represents a new and therefore unfamiliar synthetic ruby on the market, we felt it would be beneficial to inform the colored stone industry of their presence through the ICA Early Warning Alert system.
Gemological properties
The three sample stones tested, weighed 1.69, 0.69 and 0.62 ct. possessing colors ranging from Burma to Thai types with high saturations and medium to dark tones. Standard gemological testing revealed properties of refractive index (1.76-1.77), birefringence (0.008), specific gravity (3.99-4.00), UV fluorescence (LW: weak-med, red; SW: inert-weak red) and spectrum, consistent with other natural and synthetic rubies.
Microscopic examination revealed the presence of very strong graining features throughout the stone. These graining features are visually reminiscent of the type of graining observed in the Russian production of hydrothermal synthetic emeralds. In most directions, this graining is generally in a striated pattern, although in one direction the graining takes on a strongly roiled appearance resembling an aggregation of graining features. The presence of this graining is so strong, as to have an effect of slightly reducing the transparency of the stone enough to give it a sleepy appearance. This also caused a slightly diffused image of the pavilion back facet edges when viewed through the table. Certain fluctuations of color zoning could also be observed interwoven with the graining patterns. Distinctive as well were the presence of numerous, small, golden colored, highly reflective metallic inclusions. These inclusions were present in small collective groups as well as sparsely located individually. Additionally observed were healed fracture systems creating fingerprint inclusions which occasionally contained a secondary gas phase and other fracture systems.
Discussion
While these rubies represent a completely new kind of synthetic which could be encountered in the market today, their identification should not prove to be difficult. Just as with other synthetic rubies, mass sampling by means of UV fluorescence will not separate these synthetics from their natural counterparts. Microscopic examination identifying the very strong graining features which are unlike any of the swirled or planar growth characteristics observed in natural rubies from various localities and the presence of golden colored metallic inclusions, provide clear and easy proof of the synthetic origin for these hydrothermally grown rubies.
Background
During the Fall season of 1991, we first became aware of a production of hydrothermal synthetic rubies being made in Russia. At that time, we were informed that the production was only consisting of very small stones and therefore this seemed to be more of a scientific than commercial interest. During the next year and a half, we did not receive any additional information concerning further developments of this product. While on a recent trip to Bangkok though three samples were acquired which were reportedly from a recent production of Russian hydrothermal synthetic rubies. Seeing as how this represents a new and therefore unfamiliar synthetic ruby on the market, we felt it would be beneficial to inform the colored stone industry of their presence through the ICA Early Warning Alert system.
Gemological properties
The three sample stones tested, weighed 1.69, 0.69 and 0.62 ct. possessing colors ranging from Burma to Thai types with high saturations and medium to dark tones. Standard gemological testing revealed properties of refractive index (1.76-1.77), birefringence (0.008), specific gravity (3.99-4.00), UV fluorescence (LW: weak-med, red; SW: inert-weak red) and spectrum, consistent with other natural and synthetic rubies.
Microscopic examination revealed the presence of very strong graining features throughout the stone. These graining features are visually reminiscent of the type of graining observed in the Russian production of hydrothermal synthetic emeralds. In most directions, this graining is generally in a striated pattern, although in one direction the graining takes on a strongly roiled appearance resembling an aggregation of graining features. The presence of this graining is so strong, as to have an effect of slightly reducing the transparency of the stone enough to give it a sleepy appearance. This also caused a slightly diffused image of the pavilion back facet edges when viewed through the table. Certain fluctuations of color zoning could also be observed interwoven with the graining patterns. Distinctive as well were the presence of numerous, small, golden colored, highly reflective metallic inclusions. These inclusions were present in small collective groups as well as sparsely located individually. Additionally observed were healed fracture systems creating fingerprint inclusions which occasionally contained a secondary gas phase and other fracture systems.
Discussion
While these rubies represent a completely new kind of synthetic which could be encountered in the market today, their identification should not prove to be difficult. Just as with other synthetic rubies, mass sampling by means of UV fluorescence will not separate these synthetics from their natural counterparts. Microscopic examination identifying the very strong graining features which are unlike any of the swirled or planar growth characteristics observed in natural rubies from various localities and the presence of golden colored metallic inclusions, provide clear and easy proof of the synthetic origin for these hydrothermally grown rubies.
Diamond Fracture Filling Extensive Treatment, Subtle Features
(via ICA Early Warning Flash, No.68, April 5, 1993) GIA GTL writes:
Background
The diamond described herein is a 0.88 carat heat-shaped brilliant that was initially submitted to the GIA Gem Trade Laboratory for grading. During preliminary examination, however, a staff gemologist noted at first appeared to be an extremely low relief fingerprint inclusion containing minute voids. As this would be very atypical for diamond, the stone was brought to the identification and research lab for investigation.
Microscopic features
Examination under magnification using standard darkfield illumination revealed several very transparent, colorless, filled fractures. These all contained minute voids as mentioned above, as well very subtle orange and, to a lesser extent, blue flash effects. Difficulty in detecting these effects was compounded by the very shallow angles of the fractures to the surface of the diamond.
The treatment became more apparent when a pinpoint fiber optic illuminator was used. This lighting technique revealed the extent of the filled breaks, including one very large fracture beneath and nearly parallel to the table. The intense illumination made the flash effects significantly more noticeable, as well as revealing hairline fractures in the filling material. The outlines of the filled areas were also found to be easier to detect when examined in transmitted lighting with a single polarizing filter placed between the microscope’s objectives and the diamond.
Additional testing
Qualitative chemical analysis using energy dispersive X-ray fluorescence detected lead, an element previously detected in diamond fillings, X-radiography further confirmed the presence of the filling in the form of white, X-ray opaque areas on the radiograph.
Discussion
Although the diamond under investigation contained extensive filled fractures, the diagnostic microscopic features of the treatment were quite subtle. These might easily be overlooked if only darkfield illumination were used. It is therefore recommended that additional lighting techniques be used when examining diamonds for possible filled breaks, including pinpoint fiberoptic illumination and polarized light.
Background
The diamond described herein is a 0.88 carat heat-shaped brilliant that was initially submitted to the GIA Gem Trade Laboratory for grading. During preliminary examination, however, a staff gemologist noted at first appeared to be an extremely low relief fingerprint inclusion containing minute voids. As this would be very atypical for diamond, the stone was brought to the identification and research lab for investigation.
Microscopic features
Examination under magnification using standard darkfield illumination revealed several very transparent, colorless, filled fractures. These all contained minute voids as mentioned above, as well very subtle orange and, to a lesser extent, blue flash effects. Difficulty in detecting these effects was compounded by the very shallow angles of the fractures to the surface of the diamond.
The treatment became more apparent when a pinpoint fiber optic illuminator was used. This lighting technique revealed the extent of the filled breaks, including one very large fracture beneath and nearly parallel to the table. The intense illumination made the flash effects significantly more noticeable, as well as revealing hairline fractures in the filling material. The outlines of the filled areas were also found to be easier to detect when examined in transmitted lighting with a single polarizing filter placed between the microscope’s objectives and the diamond.
Additional testing
Qualitative chemical analysis using energy dispersive X-ray fluorescence detected lead, an element previously detected in diamond fillings, X-radiography further confirmed the presence of the filling in the form of white, X-ray opaque areas on the radiograph.
Discussion
Although the diamond under investigation contained extensive filled fractures, the diagnostic microscopic features of the treatment were quite subtle. These might easily be overlooked if only darkfield illumination were used. It is therefore recommended that additional lighting techniques be used when examining diamonds for possible filled breaks, including pinpoint fiberoptic illumination and polarized light.
Diffusion Treated Corundum In Pink To Red To Purple Color Range
(via ICA Early Warning Flash, No.69, May 14, 1993) GIA GTL writes:
Background
The diffusion treated stones described herein were provided for examination by United Radiant Applications, a Southern California-based firm that has been involved in the commercial production of blue diffusion treated sapphires. The faceted specimens, which included 27 stones in the red to pink to purple color range, were made available so that their gemological properties and identification criteria could be documented prior to any commercial release.
Visual appearance
Face-up some of the stones appear uniform in color, while other exhibit uneven color distribution, the latter apparently due to an absence of color on some pavilion facets.
Magnification
A number of features previously documented with blue diffusion treated sapphires were noted in these stones. These include uneven coloration from one facet to another, color concentrations in surface-reaching cavities and fractures, and color reinforcement of facet junctions, although the latter was often significantly more subtle than what we have encountered with blue diffusion-treated stones. Also noted was a type of surface and near surface damage, including minute spherical voids that we had not previously documented in blue diffusion treated sapphires.
Refractive indices
Values were generally higher than those normal for corundum, including some reading over the limits of the conventional refractometer (1.80 +).
Pleochroism
Some stones exhibited atypical dichroism, including a brownish yellow dichroic color.
Short wave UV luminescence
The majority of the stones showed a patchy bluish white luminescence to this wavelength at the surface that was sometimes confined to specific facets or groups of facets.
Absorption spectra
These were generally consistent with those of both natural and synthetic corundums of comparable color, although some absorption features were less pronounced.
Discussion
The diffusion treated corundums described herein are not difficult to identify. Key features include unusually high refractive index readings, atypical dichroism and UV luminescence, patchy surface coloration, color concentrations along facet junctions, and spherical voids just below the surface.
Background
The diffusion treated stones described herein were provided for examination by United Radiant Applications, a Southern California-based firm that has been involved in the commercial production of blue diffusion treated sapphires. The faceted specimens, which included 27 stones in the red to pink to purple color range, were made available so that their gemological properties and identification criteria could be documented prior to any commercial release.
Visual appearance
Face-up some of the stones appear uniform in color, while other exhibit uneven color distribution, the latter apparently due to an absence of color on some pavilion facets.
Magnification
A number of features previously documented with blue diffusion treated sapphires were noted in these stones. These include uneven coloration from one facet to another, color concentrations in surface-reaching cavities and fractures, and color reinforcement of facet junctions, although the latter was often significantly more subtle than what we have encountered with blue diffusion-treated stones. Also noted was a type of surface and near surface damage, including minute spherical voids that we had not previously documented in blue diffusion treated sapphires.
Refractive indices
Values were generally higher than those normal for corundum, including some reading over the limits of the conventional refractometer (1.80 +).
Pleochroism
Some stones exhibited atypical dichroism, including a brownish yellow dichroic color.
Short wave UV luminescence
The majority of the stones showed a patchy bluish white luminescence to this wavelength at the surface that was sometimes confined to specific facets or groups of facets.
Absorption spectra
These were generally consistent with those of both natural and synthetic corundums of comparable color, although some absorption features were less pronounced.
Discussion
The diffusion treated corundums described herein are not difficult to identify. Key features include unusually high refractive index readings, atypical dichroism and UV luminescence, patchy surface coloration, color concentrations along facet junctions, and spherical voids just below the surface.
Mixed Diamonds & Octahedral Cubic Zirconia Baguettes
(via ICA Early Warning Flash, No.73, August 13, 1993) GII writes:
Recently we have encountered in a packet of rough diamond one octahedral shaped cubic zirconia. The person who had done this also must be having some idea of crystallography for he has taken the trouble to etch out trigons on the octahedral faces. Fortunately, the trigons are parallel to the sides of the octahedral faces, whereas in diamonds they are not; this gave us the first doubt and other tests confirmed our suspicion.
Another interesting case of cubic zirconia fraud has also been detected at our laboratory. In a packet of diamond baguettes as well as round brilliant same sized cubic zirconia baguettes and round brilliants were detected. The suspicion was first triggered off when similar dimension baguettes were weighing 0.029 carats and some 0.05. The difference was obvious when the weight of some more number of pieces was compared and other tests were performed.
Recently we have encountered in a packet of rough diamond one octahedral shaped cubic zirconia. The person who had done this also must be having some idea of crystallography for he has taken the trouble to etch out trigons on the octahedral faces. Fortunately, the trigons are parallel to the sides of the octahedral faces, whereas in diamonds they are not; this gave us the first doubt and other tests confirmed our suspicion.
Another interesting case of cubic zirconia fraud has also been detected at our laboratory. In a packet of diamond baguettes as well as round brilliant same sized cubic zirconia baguettes and round brilliants were detected. The suspicion was first triggered off when similar dimension baguettes were weighing 0.029 carats and some 0.05. The difference was obvious when the weight of some more number of pieces was compared and other tests were performed.
Synthetic Diamonds: Rough And Treated, Faceted
(via ICA Early Warning Flash, No.74, August 13, 1993) GIA GTL writes:
Background
Recently a 0.74 carat yellow rough crystal was submitted to the GIA Gem Trade Laboratory in New York for routine identification. Shortly thereafter, a 0.55 carat dark brownish orangy red round brilliant was submitted to GIA GTL for an origin of color determination. Examination of both specimens revealed that they were synthetic diamonds. It was further determined that the rough specimen had been annealed and that the faceted one had been irradiated and subsequently annealed.
Appearance
The habit of the rough crystal was predominantly cubic, with some octahedral and dodecahedral faces. Smooth cube, and to a lesser extent, dodecahedral, faces are seen only on synthetic diamonds.
Magnification/magnetism
Both the rough and faceted pieces contained fairly large inclusions with a metallic luster. When suspended at the end of a thread, both were attached to a magnet, actually attaching to it. This reaction has been noted to date only with synthetic diamonds containing large, magnetic inclusions derived from the metallic flux in which they are produced.
The two showed similar patterns of ultraviolet luminescence and color zoning, forming essentially a square; the faceted piece also revealed this in the form of graining. This growth pattern was centered roughly in the middle of the base of the crystal and on the table of the round brilliant. Octagonal to square patterns are commonly seen in synthetic diamonds, but not in natural diamonds.
Ultraviolet luminescence
The ultraviolet luminescence of both pieces was stronger in short wave than long wave radiation. They both emitted a moderate to strong green fluorescence along the pattern described above in short wave UV radiation, with a weaker green reaction in long wave. The round brilliant also emitted a moderate orange fluorescence in short wave. Gem quality yellow synthetic diamonds previously examined by GIA Research and GIA GTL personnel have shown luminescence in short wave exclusively. The reactions noted in the two specimens under discussion would therefore appear to be from a source other than those we have previously documented in the gemological literature.
UV/Visible/IR spectroscopy
Spectroscopy helped to further characterize the specimens. Infrared spectroscopy showed them both to be essentially type Ib, as are most yellow synthetic diamonds. However, they both also showed a IaA character. This has not previously been observed in gem quality synthetic diamonds.
In the visible range, the round brilliant showed a number of sharp lines between 500 and 700bn at liquid nitrogen temperature. These features were noted both in the hand held spectroscope and on the chart of the spectrometer. Some of these lines have never been observed in natural diamond but have been reported in synthetic diamonds.
Finally, the presence of the features typical of treated pink diamonds in the spectrum of the red brilliant (in addition to other lines mentioned above) and a small HIb peak in the infrared prove that it had been irradiated and subsequently annealed. The yellow crystal also shows a line at about 637nm, which suggests that it, too, had been subjected to annealing.
Conclusion
The above characteristics clearly identify both the crystal and round brilliant as synthetic diamonds. However, some of their properties are slightly different from what we have observed before in yellow gem quality synthetic diamonds. Interestingly, virtually all the features noted are consistent with those of a group of Russian yellow synthetic diamonds currently being studied by GIA Research and the GIA GTL.
Background
Recently a 0.74 carat yellow rough crystal was submitted to the GIA Gem Trade Laboratory in New York for routine identification. Shortly thereafter, a 0.55 carat dark brownish orangy red round brilliant was submitted to GIA GTL for an origin of color determination. Examination of both specimens revealed that they were synthetic diamonds. It was further determined that the rough specimen had been annealed and that the faceted one had been irradiated and subsequently annealed.
Appearance
The habit of the rough crystal was predominantly cubic, with some octahedral and dodecahedral faces. Smooth cube, and to a lesser extent, dodecahedral, faces are seen only on synthetic diamonds.
Magnification/magnetism
Both the rough and faceted pieces contained fairly large inclusions with a metallic luster. When suspended at the end of a thread, both were attached to a magnet, actually attaching to it. This reaction has been noted to date only with synthetic diamonds containing large, magnetic inclusions derived from the metallic flux in which they are produced.
The two showed similar patterns of ultraviolet luminescence and color zoning, forming essentially a square; the faceted piece also revealed this in the form of graining. This growth pattern was centered roughly in the middle of the base of the crystal and on the table of the round brilliant. Octagonal to square patterns are commonly seen in synthetic diamonds, but not in natural diamonds.
Ultraviolet luminescence
The ultraviolet luminescence of both pieces was stronger in short wave than long wave radiation. They both emitted a moderate to strong green fluorescence along the pattern described above in short wave UV radiation, with a weaker green reaction in long wave. The round brilliant also emitted a moderate orange fluorescence in short wave. Gem quality yellow synthetic diamonds previously examined by GIA Research and GIA GTL personnel have shown luminescence in short wave exclusively. The reactions noted in the two specimens under discussion would therefore appear to be from a source other than those we have previously documented in the gemological literature.
UV/Visible/IR spectroscopy
Spectroscopy helped to further characterize the specimens. Infrared spectroscopy showed them both to be essentially type Ib, as are most yellow synthetic diamonds. However, they both also showed a IaA character. This has not previously been observed in gem quality synthetic diamonds.
In the visible range, the round brilliant showed a number of sharp lines between 500 and 700bn at liquid nitrogen temperature. These features were noted both in the hand held spectroscope and on the chart of the spectrometer. Some of these lines have never been observed in natural diamond but have been reported in synthetic diamonds.
Finally, the presence of the features typical of treated pink diamonds in the spectrum of the red brilliant (in addition to other lines mentioned above) and a small HIb peak in the infrared prove that it had been irradiated and subsequently annealed. The yellow crystal also shows a line at about 637nm, which suggests that it, too, had been subjected to annealing.
Conclusion
The above characteristics clearly identify both the crystal and round brilliant as synthetic diamonds. However, some of their properties are slightly different from what we have observed before in yellow gem quality synthetic diamonds. Interestingly, virtually all the features noted are consistent with those of a group of Russian yellow synthetic diamonds currently being studied by GIA Research and the GIA GTL.
Saturday, April 21, 2007
Polymer-impregnated Jadeite
(via ICA Early Warning Flash, No.75, November 23, 1993) GIA GTL writes:
Background
Over the last several years polymer-impregnated jadeite has become prevalent in the jade market. This has given rise to some colors of jadeite being routinely tested for the presence of this treatment.
Recently, the GIA GTL in Santa Monica received for identification a 15 carat purple oval cabochon that we identified as jadeite. Subsequent testing determined the stone to be polymer impregnated. To the best of our knowledge, this is the first report of a jadeite of this color that is polymer-impregnated.
Polymer-impregnated ‘lavender’ jadeite
Gemological properties: Gemological testing revealed an index of refraction and visible absorption spectrum consistent with jadeite jade. Specific gravity was measured by the hydrostatic method and determined to be 3.32, which is slightly lower than the norm for jadeite. This is consistent with previous findings of polymer-impregnated jadeite. The stone was inert to longwave ultraviolet radiation. Magnification did not reveal any evidence of treatment. As is often the case with purple jadeite, the origin of the color could be be determined.
Infrared spectroscopy
The spectrum of this stone reveals intense absorptions around 2900cm¯¹ which are not found in natural jadeite. These additional features are due to the presence of an ‘opticon-like’ polymer. This is not surprising, since this type of polymer is the most commonly employed for jadeite impregnation, according to many reports and our own experience.
Discussion
This finding is particularly significant since none of the polymer-impregnated jadeite (or B jade) we have seen so far was purple in color. They have all been green or mottled green and white, some with applied spots of brown. This means that we will now have to expand our routine testing for polymer impregnation to include purple jadeites as well.
New polymers for jadeite impregnation
We have recently encountered two new types of polymer used for the treatment of jadeite, in addition to the three previously described which are wax, an ‘opticon-like’ polymer, and phthalate-like polymer. Since we do not know yet their exact nature, we will refer to them as polymer 4 and polymer 5.
Polymer 4
The infrared spectrum of polymer 4 is very similar—but not identical—to that of wax. In particular, the major absorption is slightly shifted and of different width than that for wax. Jadeites treated with this product do not ‘sweat’ when tested with the thermal reaction tester, as opposed to those impregnated with wax which do. We measured the SG of one stone showing this kind of impregnation at 3.33.
Polymer 5
The infrared spectrum of polymer 5 shows similar absorption features as polymer 4, plus five more in the range of 2950-3150 cm¯¹. The three jadeites impregnated with this material that we studied are inert in ultraviolet radiation. We could measure the SG on only one of them, and the stone floated in the 3.32 SG liquid (methylene iodide). It is interesting to note that two of these stones displayed ‘sweating’ when tested with T.R.T.
Conclusion
These two new polymers have been seen on a few jadeites submitted for identification, and laboratories involved in B-jade detection should be aware of them. They demonstrate the growing variety of polymers that are being used for jade treatment. One reason for this could be the increasing number of companies involved in this treatment.
Background
Over the last several years polymer-impregnated jadeite has become prevalent in the jade market. This has given rise to some colors of jadeite being routinely tested for the presence of this treatment.
Recently, the GIA GTL in Santa Monica received for identification a 15 carat purple oval cabochon that we identified as jadeite. Subsequent testing determined the stone to be polymer impregnated. To the best of our knowledge, this is the first report of a jadeite of this color that is polymer-impregnated.
Polymer-impregnated ‘lavender’ jadeite
Gemological properties: Gemological testing revealed an index of refraction and visible absorption spectrum consistent with jadeite jade. Specific gravity was measured by the hydrostatic method and determined to be 3.32, which is slightly lower than the norm for jadeite. This is consistent with previous findings of polymer-impregnated jadeite. The stone was inert to longwave ultraviolet radiation. Magnification did not reveal any evidence of treatment. As is often the case with purple jadeite, the origin of the color could be be determined.
Infrared spectroscopy
The spectrum of this stone reveals intense absorptions around 2900cm¯¹ which are not found in natural jadeite. These additional features are due to the presence of an ‘opticon-like’ polymer. This is not surprising, since this type of polymer is the most commonly employed for jadeite impregnation, according to many reports and our own experience.
Discussion
This finding is particularly significant since none of the polymer-impregnated jadeite (or B jade) we have seen so far was purple in color. They have all been green or mottled green and white, some with applied spots of brown. This means that we will now have to expand our routine testing for polymer impregnation to include purple jadeites as well.
New polymers for jadeite impregnation
We have recently encountered two new types of polymer used for the treatment of jadeite, in addition to the three previously described which are wax, an ‘opticon-like’ polymer, and phthalate-like polymer. Since we do not know yet their exact nature, we will refer to them as polymer 4 and polymer 5.
Polymer 4
The infrared spectrum of polymer 4 is very similar—but not identical—to that of wax. In particular, the major absorption is slightly shifted and of different width than that for wax. Jadeites treated with this product do not ‘sweat’ when tested with the thermal reaction tester, as opposed to those impregnated with wax which do. We measured the SG of one stone showing this kind of impregnation at 3.33.
Polymer 5
The infrared spectrum of polymer 5 shows similar absorption features as polymer 4, plus five more in the range of 2950-3150 cm¯¹. The three jadeites impregnated with this material that we studied are inert in ultraviolet radiation. We could measure the SG on only one of them, and the stone floated in the 3.32 SG liquid (methylene iodide). It is interesting to note that two of these stones displayed ‘sweating’ when tested with T.R.T.
Conclusion
These two new polymers have been seen on a few jadeites submitted for identification, and laboratories involved in B-jade detection should be aware of them. They demonstrate the growing variety of polymers that are being used for jade treatment. One reason for this could be the increasing number of companies involved in this treatment.
Yellow And Orange Sapphires
(via ICA Lab Alert, No.1, June 2, 1987) AIGS writes:
Background
In 1981, we at AIGS were asked to identify what was undoubtedly among the first heat treated Sri Lankan yellows to come out of ovens of Bangkok. We were told that the stone was treated by an unknown process (which was later found to be heat), and were asked to determine the color stability. This we proceeded to do by performing our usual fade test. This consisted of exposing the stone to heat and light at 1cm distance of a 150 watt spotlight for up to one hour. We were truly surprised when, after a few minutes exposure, the color had become much darker and more brownish (stones treated with irradiation would fade; some untreated Sri Lankan yellows will fade, but in most the color will not change). This change was temporary only; as the stone cooled to room temperature the color returned to normal.
Since this time we have tested over a thousand Sri Lankan yellow/orange sapphires and have found that all of the heat treated yellow to orange stones react in this way. Thus, a simple test for detection of heat treatment in Sri Lankan yellow/orange sapphires is possible.
The test
Place the stone in close proximetry to a source of mild source of heat, such as an incandescent bulb.
Results
Heat treated Sri Lankan yellow/orange sapphire —The color darkens temporarily, becoming more brownish. The deeper the original color, the greater the change. As the stone cools, the color returns to its original state. Control stones should be used so as to detect even slight changes in color.
Irradiated Sri Lankan yellow/orange sapphire —The color will fade, usually within one hour.
Untreated Sri Lankan yellow/orange sapphire —Generally no change, however some stones may show some fading.
Thai/Australian yellow/orange sapphire, heat treated or untreated—no change has been observed in the color of these stones.
(To: Mr N Horiuchi; Subject: Response to comment on Lab Alert No.1) AIGS writes:
Discussion
Mr N Horiuchi has commented on the test we previously described in Lab Alert No.1 to detect heat treatment in Sri Lankan yellow/orange sapphires. Mr Horiuchi stated that this color also did not fade under the same condition as reported on (by) AIGS.
From the above statement it appears that Mr Horiuchi has not understood the text of Lab Alert No.1. As others may also have misunderstood the text, we will describe the test again below.
Heat treatment in Sri Lankan yellow to orange sapphires may be detected by applying a simple fade test. (Caution: This test only works for Sri Lankan stones). Once a yellow/orange sapphire has been identified as definitely originating from Sri Lanka, its color is tested by applying a simple fade test. The stone in question should be placed on a glass (or other nonflammable) platform within ½ cm of a hot 150 watt (or more) spotlight. The idea is to expose the stone to lots of light and heat. After about 15 minutes exposure (as the stone heats up), the color of a heat treated yellow/orange sapphire will have been found to have become slightly darker and more brownish (the deeper the starting color before the test, the deeper and more brownish the color after heating up). This change is temporary only. As the stone cools its color will fade back to the color before the test was started, not, we repeat, not back to the color before the stone was heat treated (by someone else presumably). We believe that is where Mr Horiuchi misunderstood the original Lab Alert.
Other possible reactions
If the stone has been irradiated (either by nature or by man) the color will fade, usually within one hour’s exposure. In most natural Sri Lankan sapphires, however, the color will show no change. Natural yellow/orange sapphires from other sources and synthetic yellow/orange sapphires also show no change.
To make this test more accurate, control stones of similar color to the stone being tested should be used. Then after the stone in question heats up it can be compared to the color of the control stone. In the case of heat treated yellow/orange Sri Lankan sapphires, the change is not subtle in deeply colored stones, and anyone with normal vision should easily detect it, but the comparison must be made quickly before the stone tested cools down.
Dr Kurt Nassau has informed us that under certain conditions, yellow/orange sapphires may get darker upon exposure to some kinds of visible light. We have absolutely no information on exactly what kinds of stones do this or under what conditions. However he has promised us that the subject will be described in detail soon in an article he has written for Gems & Gemology. We have also written an article on the subjects covered in Lab Alerts Nos. 1 and 2 and submitted it to Gems & Gemology. We don’t know when it will appear (or if it will appear). We have had no reply of any kind, even though we sent it 8 weeks ago.
The subject of color in yellow sapphires is extremely complex. We have no illusions that the above information is the last word on the subject. However, over the past ten years we have tested thousands of pieces of yellow/orange sapphire from all sources and this is what we have found. If anyone else could she additional light on the subject, we would love to hear from them.
Dr K Schmetzer replies:
A. Fe³+ or by Fe³+ and Ti³+: Type 1, originating from Nigeria, Thailand, Australia or
B. By a yellow color center: Type 2, originating from Sri Lanka.
By heat or irradiation heat treatment, yellow stones with similar color centers, i.e with absorption spectrum similar to the spectrum of Type 2, but with different stabilities to light or heat are produced.
C. Irradiation treatment, color center: Type 3
D. Heat treatment, color center: Type 4
According to my experience and knowledge, AIGS describes a test for Type 4 stones, and N Horiuchi is dealing with Type 3 stones. Dr Nassau describes Type 2 stones in Alert No.9, and this type of yellow color center may be connected with natural irradiation. The reason for the higher stability of this naturally irradiated yellow compared to artificially irradiated yellow is an unknown but similar results were found by myself with natural irradiated yellow quartz (citrine) and artificially irradiated yellow quartz.
Background
In 1981, we at AIGS were asked to identify what was undoubtedly among the first heat treated Sri Lankan yellows to come out of ovens of Bangkok. We were told that the stone was treated by an unknown process (which was later found to be heat), and were asked to determine the color stability. This we proceeded to do by performing our usual fade test. This consisted of exposing the stone to heat and light at 1cm distance of a 150 watt spotlight for up to one hour. We were truly surprised when, after a few minutes exposure, the color had become much darker and more brownish (stones treated with irradiation would fade; some untreated Sri Lankan yellows will fade, but in most the color will not change). This change was temporary only; as the stone cooled to room temperature the color returned to normal.
Since this time we have tested over a thousand Sri Lankan yellow/orange sapphires and have found that all of the heat treated yellow to orange stones react in this way. Thus, a simple test for detection of heat treatment in Sri Lankan yellow/orange sapphires is possible.
The test
Place the stone in close proximetry to a source of mild source of heat, such as an incandescent bulb.
Results
Heat treated Sri Lankan yellow/orange sapphire —The color darkens temporarily, becoming more brownish. The deeper the original color, the greater the change. As the stone cools, the color returns to its original state. Control stones should be used so as to detect even slight changes in color.
Irradiated Sri Lankan yellow/orange sapphire —The color will fade, usually within one hour.
Untreated Sri Lankan yellow/orange sapphire —Generally no change, however some stones may show some fading.
Thai/Australian yellow/orange sapphire, heat treated or untreated—no change has been observed in the color of these stones.
(To: Mr N Horiuchi; Subject: Response to comment on Lab Alert No.1) AIGS writes:
Discussion
Mr N Horiuchi has commented on the test we previously described in Lab Alert No.1 to detect heat treatment in Sri Lankan yellow/orange sapphires. Mr Horiuchi stated that this color also did not fade under the same condition as reported on (by) AIGS.
From the above statement it appears that Mr Horiuchi has not understood the text of Lab Alert No.1. As others may also have misunderstood the text, we will describe the test again below.
Heat treatment in Sri Lankan yellow to orange sapphires may be detected by applying a simple fade test. (Caution: This test only works for Sri Lankan stones). Once a yellow/orange sapphire has been identified as definitely originating from Sri Lanka, its color is tested by applying a simple fade test. The stone in question should be placed on a glass (or other nonflammable) platform within ½ cm of a hot 150 watt (or more) spotlight. The idea is to expose the stone to lots of light and heat. After about 15 minutes exposure (as the stone heats up), the color of a heat treated yellow/orange sapphire will have been found to have become slightly darker and more brownish (the deeper the starting color before the test, the deeper and more brownish the color after heating up). This change is temporary only. As the stone cools its color will fade back to the color before the test was started, not, we repeat, not back to the color before the stone was heat treated (by someone else presumably). We believe that is where Mr Horiuchi misunderstood the original Lab Alert.
Other possible reactions
If the stone has been irradiated (either by nature or by man) the color will fade, usually within one hour’s exposure. In most natural Sri Lankan sapphires, however, the color will show no change. Natural yellow/orange sapphires from other sources and synthetic yellow/orange sapphires also show no change.
To make this test more accurate, control stones of similar color to the stone being tested should be used. Then after the stone in question heats up it can be compared to the color of the control stone. In the case of heat treated yellow/orange Sri Lankan sapphires, the change is not subtle in deeply colored stones, and anyone with normal vision should easily detect it, but the comparison must be made quickly before the stone tested cools down.
Dr Kurt Nassau has informed us that under certain conditions, yellow/orange sapphires may get darker upon exposure to some kinds of visible light. We have absolutely no information on exactly what kinds of stones do this or under what conditions. However he has promised us that the subject will be described in detail soon in an article he has written for Gems & Gemology. We have also written an article on the subjects covered in Lab Alerts Nos. 1 and 2 and submitted it to Gems & Gemology. We don’t know when it will appear (or if it will appear). We have had no reply of any kind, even though we sent it 8 weeks ago.
The subject of color in yellow sapphires is extremely complex. We have no illusions that the above information is the last word on the subject. However, over the past ten years we have tested thousands of pieces of yellow/orange sapphire from all sources and this is what we have found. If anyone else could she additional light on the subject, we would love to hear from them.
Dr K Schmetzer replies:
A. Fe³+ or by Fe³+ and Ti³+: Type 1, originating from Nigeria, Thailand, Australia or
B. By a yellow color center: Type 2, originating from Sri Lanka.
By heat or irradiation heat treatment, yellow stones with similar color centers, i.e with absorption spectrum similar to the spectrum of Type 2, but with different stabilities to light or heat are produced.
C. Irradiation treatment, color center: Type 3
D. Heat treatment, color center: Type 4
According to my experience and knowledge, AIGS describes a test for Type 4 stones, and N Horiuchi is dealing with Type 3 stones. Dr Nassau describes Type 2 stones in Alert No.9, and this type of yellow color center may be connected with natural irradiation. The reason for the higher stability of this naturally irradiated yellow compared to artificially irradiated yellow is an unknown but similar results were found by myself with natural irradiated yellow quartz (citrine) and artificially irradiated yellow quartz.
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