Short Cuts To Certainty

2007: B W Anderson is a giant in gemology. This is an excellent article for students, gem traders, lab gemologists and consumers. The methodology is simple and straightforward. Many in the trade do not understand lab gemologist's problems. The trade and consumers want quick results; they want lab gemologists to make god-like statements. To detect intruders in a mixed parcel of colored stones requires insight, knowledge, analytical skills and speed. This skill will come only with discipline, experience and guerilla concentration. Today's gemologists will have to be familiar with new synthetics, treated stones, and a variety of simulants very different from the 1970s.

(via The Australian Gemmologist, Vol.12. No.2, May 1974) B W Anderson writes:

The procedure when testing gemstones in a busy trade laboratory, such as that in which I spent all my professional life, must of necessity differ radically from the adopted by a student. And this difference does not depend so much on the apparatus available as upon the purpose of the exercise. The student’s chief task is to learn; the professional’s task is, above all, to identify.

For the student it is both interesting and advisable to study each specimen in an orderly and planned manner, beginning in most cases with the determination of its refractive indices on the refractometer, and continuing with a study of its inclusions under the microscope, its absorption of light by means of the spectroscope, its dichroism, and so on. There may even be time for an accurate determination of its specific gravity. By doing all this, the young gemologist becomes accustomed to handling all his instruments, and gradually learns from first-hand the properties of each gem variety. The values he measures cease to be figures in a textbook and become recognized as living attributes of the stones concerned. If his teacher is wise he will also become trained in the intelligent use of a 10x lens, which alone can be his constant companion outside the laboratory, and with which so many gemological decisions can be made without resort to more elaborate instruments.

For the laboratory gemologists, while the first essential is of an accurate appraisal of each specimen, the next and pressing necessity is for speed. Once he has achieved a conclusive result he may have to deny himself the pleasure of further examining a stone in all its fascinating aspects, and after completing his report, must pass on to the next test. So often it seems that his client is waiting to known his decision before signing a cheque to conclude a deal.

There will usually be a wide choice of test available, but, after careful preliminary inspection (which in itself may prove conclusive) the expert must decide which test or tests will provide him with a specific answer. Since commercial gem testing so often consists in distinguishing between natural and synthetic stones, the refractometer is seldom needed, which is just as well as, however carefully handled, the soft glass of that instrument soon becomes marred by scratches and must then be repolished. A refractometer on which 1000 stones have been tested will certainly need repair while, in contrast, a micrometer or spectroscope through which a hundred times that number have been examined will have suffered no ill effects.

The nature of the goods will often dictate the first step in testing quite clearly. For example, where hundreds of small rubies are submitted it will be a valid assumption that the stones are all red corundums, the point at issue being whether they are natural or synthetic. The gemologist will therefore turn first to the microscope, knowing that in the course of examination of the stones under magnification he will, as an experienced gemologist, be able to satisfy himself as to both the origin and the species. Initially the stones can be examined in the dry state suitably distributed in lines on a glass plate. Any stones which do not at once show distinctive features can be put on one side for more thorough examination, either under oil immersion or by alternative methods.

To take another instance—a parcel of stones purporting to be tourmalines. In this case the stones would clearly be destined for a refractometer test, since here the microscope would of little value since there are (thank goodness) no synthetic tourmalines yet available, and refractive index and birefringence measurements will provide the definite answer required. In passing, one may remark that in testing such stones as tourmaline, quartz or beryl, which have a low R.I, it is very advantageous to use a Rayner ‘spinel’ refractometer, since this gives easy readings to three places of decimals in ordinary white light and suffers hardly any mechanical damage.

It is much difficult to decide a plan of action where a large parcel of mixed stones is to be tested, or a brooch or necklace set with a variety of stones, as each species may well need a different approach, and it is tedious and time consuming to be moving constantly from one instrument to another. In the case of a large parcel of mixed stones it may indeed be worth while to begin by sorting the stones by eye into groups which appear to be of the same type, after which the determination of each group will be far more rapid. Where the majority of stones in a parcel or group are all of one kind there are several ways in which any ‘intruders’ may be rapidly detected. For example, when in a parcel of yellow topaz stones some citrines have intruded, a flotation test in a bromoform solution will quickly separate them, and another useful technique is to make plain any differences in refractive index by immersion in a suitable liquid. One such case was clearly demonstrated when a contact photograph was made of a necklace consisting mainly of colored tourmaline beads. In this case the necklace was immersed in bromobenzene (R.I=1.56) in a glass dish under which a slow photographic film was placed in a dark room and exposed for a few seconds to an overhead light. The print from the developed film showed clearly a thick dark outline in each of the tourmaline beads indicating that their R.I was well above 1.56, whereas the five aquamarines which were mixed in with the tourmalines nearly matched the liquid in R.I and showed hardly any outline, making them very easy to distinguish.

Sometimes the detection of ‘intruders’ may be accomplished in a quite unorthodox manner. I can remember when some 30 years ago I had to test a packet of 117 small green stones, labeled ‘dark olivines’, which a preliminary inspection revealed as being mainly demantoid garnets. Here the most rapid and positive test proved to be examination under a low power microscope. I had recently become aware of the prevalence of ‘horsetail’ asbestos fibres as an almost inevitable inclusion in demantoid garnets, and was delighted to see these most characteristic features in all but seven of the stones. These seven were then examined with a spectroscope, which enabled me to complete the test in a very short time. One stone was a ‘clean’ demantoid, two were peridots, one a green sapphire, and three were green andalusites from Brazil of that kind which show delicate absorption bands due to manganese.

Of course, even an experienced gemologist may choose a wrong approach to a problem, and is annoyed to feel that he has wasted too much time in completing a test. Mathematicians have a word for the proof of a problem which is not only sound but also rapid and incisive. They speak of such as an ‘elegant’ proof. And it is an ‘elegant’ proof that a good gemologist would always wish to choose, and which gives him real satisfaction as a craftsman and as a scientist.

In the interests of time-saving the experienced gemologist is glad to take advantage of certain features which he knows to be unique to one species or one variety of gemstone. Particularly valuable are those tests which not only determine the species of gemstone, but at the same time prove it to be natural or synthetic in origin. Such are ‘shortcuts to certainty’ referred to in the title of this article, and I will now proceed to give details of some of these which have proved of particular value in the London laboratory.

First in importance I would undoubtedly place the group of absorption bands in the blue part of the spectrum (in particular the strongest of these, at 4500 Å) which can be seen in natural sapphires. Since C J Payne and I first observed this band in 1933 we have noted its presence in many thousands of natural sapphires but never in any faceted synthetic sapphire. We thus came to regard the presence of the 4500 Å band as a valuable and undeniably proof that the stone concerned was a natural sapphire (though nowadays the possibility of a doublet consisting in part of natural sapphire must be borne in mind). The band also indicates that geographical origin of the stone to some extent, according to the content of Fe2O3 typical for each locality. Thus while Ceylon sapphires may show only a single faint and narrow band at 4500 Å, Australian stones and green sapphires show a strong and broad absorption block within which the three main bands at 4500, 4600 and 4710 Å can be discerned. Sapphires from other localities, arranged in order or increasing absorption strength, can be written thus: Burma, Kashmir, Siam, Kenya, Montana. In cases where the band is almost invisibly weak, as is often true of Ceylon stones, it is wise to confirm it by wavelength measurement to ensure that the supposed band is not a matter of imagination or wishful thinking. The Beck ‘wavelength’ spectroscope is admirable for this purpose, since the crosswires in the eyepiece can be made to traverse the spectrum by rotating a drum marked in supposed band without the observer knowing what the reading is until he looks at the scale on the drum.

Observation is greatly assisted in this part of the spectrum if the light is filtered through a flask containing strong copper sulphate solution, and, since the 4500 Å band is an ‘ordinary’ ray phenomenon, a Polaroid disc may also serve to emphasize the reality of its presence.

The 4500 Å complex is also useful in confirming that yellow sapphires from Siam (Thailand) or Australia are not synthetic corundums, as these show the bands quite strongly. In yellow sapphires from Ceylon the band is seldom visible, but here an apricot-colored fluorescence under longwave ultraviolet light is a helpful sign (as well, of course, as the inclusions which are usually present).

Looking at the problem from the synthetic side, the common reaction of synthetic blue sapphires to shortwave ultraviolet light is to show a curious whitish or greenish surface fluorescence which is so weak that it needs a darkened room and dark-adapted eyes for its observation. Since natural Ceylon sapphires have on rare occasions been known to show a similar stringent one by examining the surface of the fluorescing stone, since this frequently reveals curved structure lines, even when these are hard to see in ordinary light.

The wise gemologist will not supersede the conventional examination of sapphires under lens or microscope, which in themselves often enable him to make a sure and quick decision, but they can be enormously helpful in providing proof in the case of ‘clean’ stones showing no easily observable structures.

Short Cuts To Certainty (continued)

Variscite

(Utahlite)
Chemistry: Hydrous aluminum iron phosphate; amarice with quartz.
Crystal system: Orthorhombic; massive as nodules, cavity fillers and crusts.
Color: Semi translucent to opaque; yellow green, bluish green, greenish blue; specimens contain brownish yellow to greenish yellow matrix.
Hardness: 5
Cleavage: Perfect: 1 direction; Fracture: brittle, conchoidal.
Specific gravity: 2.55 (2.52- 2.6)
Refractive index: 1.56 mean (1.56-1.59); biaxial negative.
Luster: Massive: vitreous, dull.
Dispersion:-
Dichroism: -
Occurrence: Sedimentary (by direct deposition from phosphate-bearing water that has reacted with aluminum rich rocks in near surface environments); Australia, USA.

Notes
Sometimes called Utahlite from its USA occurrence; may look like turquoise but hardness and SG lower; spectrum: strong line at 688nm, weak line at 650nm, not diagnostic; cabochons, carvings.

Can You Identify This Stone?

(via The Canadian Gemmologist, Vol.III, No.3, Spring, 1982) . I am quite new as a faceted gemstone. I have been known for a long time as massive material, but only recently did they discover me in transparent crystals. I am strongly pleochroic, and crystallize in orthorhombic prisms. If I were a bit harder, I could pass muster as one of the so-called ‘precious’ gemstones. But my hardness of 6½ does not mean that I am cheap. What am I?
Answer: Zoisite, variety Tanzanite

Communities Dominate Brands

Good Books: (via Emergic) Tomi Ahonen and Alan Moore's Communities Dominate Brands: Business and Marketing Challenges for the 21st Century is about the new phenomenon in everything we do; from computing, blogging, videogaming, modified mobile phones and so on. It's an interesting book to read because it's happening quietly.

From the book description:
[It] is a book about how the new phenomenon of digitally connected and empowered customer-communities, such as blogging, videogaming and mobile phone smart mobs are emerging as a force to counterbalance the power of the business and marketing. The book discusses how disruptive effects of digitalisation and connectedness introduce threats to business opportunities. The authors compellingly illustrate how modern consumers are forming communities and peer-groups to pool their power resulting in a dramatic revolution of how businesses interact with their customers. The book explores the problems faced by branding, marketing and advertising in this decade.

Here is an excerpt from the foreword by Stephen Jones:
It is difficult to put a lens on a developing social trend moving as fast as connected communities but Alan and Tomi have done that. Together they have made a rare and important breakthrough insight, have developed a credible hypothesis and backed it up with validated supporting points. This is not radical misinformed extremist hype. This work is an accurate description of the issue, the opportunity and the crisis confronting marketers if they don’t cut loose the shackles of the traditional advertising agency and TV network model and explore the world of possibilities recommended by this book.

Move quickly but act thoughtfully, even slowly. You want to implement this without sending your organization into a tail spin. The traditional marketing company that wastes its investments solely on TV advertising is underpinned by bureaucratic values of safety, efficiency and control. The marketing group that embraces these insights and moves forward to implement them is underpinned by interdependent values of sharing, listening, equity rights, global harmony and synergy. That’s a big leap.

One of the chapters in the book is about Generation-C: Generation-C stands for the Community Generation. The defining and distinguishing characteristic for Gen-C is the continuous connection to and responding to digital communities. This is very different from any other communities. Even a die-hard 40 year old football fan of Chelsea may wear his colours every day and spend most of his free time with friends who are also fans. Yes, he is obviously a member of the Chelsea fan community. But when that Chelsea fan goes to visit his parents and suddenly gets into an argument, he is no longer a Chelsea community member. He probably will tell his Chelsea mates what happened, afterwards, next day at the pub. The difference is that a Gen-C member carries his/her community in the pocket and accesses that community at all times. Thus the young Gen-C member would share the anger and frustration of the argument with parents, within the next few minutes, via a text message to close friends...Members of Generation-C will regularly, on a daily basis, consult with friends and colleagues from their various communities. To do so, they have to have continous access to their network. They must be 'always-on' and only the mobile phone allows this.

For more, you can also read the blog by the authors.

Forger Back At Work - And This Time It's All Above Board

Hugh Muir writes about Robert Thwaites + the audacious frauds that stunned and embarrassed the art world + other viewpoints @ http://arts.guardian.co.uk/art/news/story/0,,2137637,00.html

The story reminds of treated/synthetic/imitation gemstones sold as natural in the gem and jewelry industry. Today only a very few may know to recognize the tell-tale signs; even the so-called trained gemologists and jewelers make spectacular mistakes. Rapid sight identification is a natural gift from the gods. One may be trained to describe the fine details but spotting an unnatural stone (s) at the right time require (s) more than textbook knowledge and diplomas. I think we are going to experience 'momentary autism' periodically forever.

De Beers After 2008: No Russian Rough – Forever!

Chaim Even-Zohar writes about the legal commitment between De Beers and Alrosa + the impact + other viewpoints @ http://www.idexonline.com/portal_FullEditorial.asp?TextSearch=&KeyMatch=0&id=25298

Aqua Aura

(via Wikipedia) Aqua Aura is a term used to describe a natural crystal that has been coated with gold fumes. It is created in a vacuum chamber from quartz crystals and gold vapor. The quartz is heated to 1600 degrees Fahrenheit in a vacuum, and then gold vapor is added to the chamber. The gold atoms fuse to the crystal's surface, which gives the crystal an iridescent metallic sheen. The process was awarded the United States Patent No. 6997014 on Feb 14, 2006. The process was invented by Steven F. Starcke, Ronald H. Kearnes and Keven E. Bennet. While the patent might have been given in 2006, this material has been produced by this method for dozens of years prior.

The patent says "The invention provides a decorative object comprising a transparent or translucent substrate having a body and at least one surface bearing a thin film coating. The coating imparts in the substrate a body color that appears substantially constant at different angles of observation. This body color is imparted in the substrate at least in part by absorption of visible radiation that is transmitted through said coating. The coating includes a high absorption layer comprising film that is highly absorptive of visible radiation. Also provided are methods of coating gems and other decorative objects, as well as methods of heat treating coated gems and other decorative objects."

Aqua Aura is a very popular item in metaphysical items and a popular item in jewellery. It is the exact same process that is used to coat steel balls used as bearings. The term Aqua aura specifically is used for the blue colored quartz. Additional elements can be used to treat quartz, such as indium, titanium and copper. The coloring of this treatment is only on the surface, so all faceted and polished material you find has been treated after it has been made originally. Often, quartz of lesser quality, with fractures and weak spots, will break apart during the coating process.

A little known fact is that the Aqua aura treatment can be used to reveal twinning in quartz crystals that would otherwise go undetected. While most all treated quartz is destined for the metaphysical marketplace, it does have a use in the field of mineralogy. (http://en.wikipedia.org/wiki/Aqua_aura)

Aqua Aura treated quartz or topaz could be visually confused for heat treated zircons because the prominent iridescence in treated specimens may be confused for dispersion. Standard gemological tests such as refractive index, birefringence and specific gravity should easily identify the stones. Also cobalt-doped blue synthetic quartz may look very similar to Aqua Aura treated stones. In this case Chelsea color filter reaction and absorption spectrum should easily provide diagnostic results; as the synthetic quartz will show pink through the Chelsea color filter + cobalt absorption spectrum. Aqua Aura treated topaz may be confused for irradiated blue topaz. In the case of quartz and topaz the unnatural iridescence is the indicator + magnification. The absence of pleochroism is also another indicator. Another interested aspect is when you study the treated quartz + topaz under proper magnification you may notice dark color concentrations of color along facet junctions + the uneven coloration very similar to blue diffusion-treated sapphires. Buyer beware!

Tugtupite

(Reindeer Stone)
Chemistry: Sodium aluminum beryllium silicate
Crystal system: Tetragonal; massive allied to sodalite; crystals rare.
Color: Various shades of red, from pale pink to violetish red and violet; may contain black needles or yellow spots; transparent materials rare, facetable material also found.
Hardness: 6.5
Cleavage: Massive: none; Fracture: granular
Specific gravity: 2.3 – 2.57; 2.3 depending on porosity and other minerals present.
Refractive index: 1.496 – 1.502; Uniaxial positive; 0.006 (0.004-0.006)
Luster: Vitreous to greasy
Dispersion:-
Dichroism: Bluish red; orange red
Occurrence: Red angular masses in Albite-rich hydrothermal veins; Greenland, Russia.

Notes
Found in 1960; ornamental stone may resemble rhodochrosite; massive is mottled white with shades of red; fluorescence: orange (LW), salmon (SW), bright red (UV); cabochon, carvings, beads.