Monday, July 09, 2007
Code of Practice Favoring Cultured Ambiguity
Chaim Even-Zohar writes about The Council for Responsible Jewellery Practices (CRJP) + its Code of Practices + gaps and shortcomings + other viewpoints @ http://www.idexonline.com/portal_FullEditorial.asp?TextSearch=&KeyMatch=0&id=26245
Sapphire Mining In Chantaburi (Thailand)
2007: Chantaburi has changed a lot since 1973. There are new types of colored stones coming from Africa, South Asia, and Southeast Asia + good quality rubies and sapphires are getting more difficult to find + foreign tourists, dealers, students are still visiting Chantaburi looking for the best deal and making mistakes.
(via The Journal of Gemmology, Vol.13, No.8, October 1973) J A L Pavitt writes:
Thailand, or Siam as it was formerly named, is a well-known source of sapphire, ruby, star-sapphire and zircon and over the years the skill of Thai lapidaries has advanced to a very high degree, making Bangkok, the capital city, an important center for the supply of cut gemstones.
There are a number of gem mining localities in Thailand, many of them in remote areas, but the mines at Chantaburi (also known as Chantabun), 200 miles from Bangkok, can be reached by car in five and a half hours, and soon after our arrival in Thailand in 1971 my wife and I made our first visit to Khau Ploi Waen, or ‘Hill of the Sapphire Ring’, as this mining area at Chantaburi is named. I have since made further visits, the most recent in January 1973 with Mr Kenneth Parkinson during his two week visit to Thailand.
Chantaburi has a very special place in the history and culture of the Kingdom of Thailand. Situated near the coast, only thirty miles from the border with Cambodia, its inhabitants, although loyal and proud Thai nationals have ethnic origins connecting many of them with the diverse civilizations which existed thousands of years ago between the borders of China and the Mekong Delta. These origins are still evident in the customs, skills, religious and dialects to be found among the people of this fertile eastern region of the Kingdom.
It was at Chantaburi that King Taksin marshaled his forces after the fall of the ancient city of Ayuthaya, and finally defeated and drove out the Burmese invaders. Close to the sapphire mines one can see the rusting cannon and remains of the fortress of King Rama III (1787 – 1851).
The gem-bearing deposits at Khau Ploi Waen are about six miles south of the town of Chantaburi, near the village of Ban Kacha. Past records indicate that in 1850 the Shans and Burmese were extracting sapphires here and that in 1850 a British Company obtained a lease but failed to make a success of the venture. In 1919 the Siam Mining Act came into force and since then mining has been solely in the hands of Thai nationals.
The mining area is privately owned and has been cleared of primary growth and planted with rubber trees, although it is obvious that an income from rubber tapping is of minor importance. A lease to dig for gemstones over an area of one ‘rai’ (approx. 0.4 acre) for one year is granted by the landlords for a fee which may be as high as baht 300000 for high yield areas which have not previously been worked. A lease is usually shared by groups or families and there are said to be some 2000 people mining around Khau Ploi Waen.
The method of extracting the stones is very primitive, as are the tools—a pick, a spade and a rattan basket. A vertical shaft of about four feet in diameter is dug in the red/brown clay soil, in between the rubber trees. These vertical shafts sometimes go as far as thirty feet deep and each basketful of soil is lifted to the surface by a crude, but effective, crane arrangement consisting of two bamboo legs and a long bamboo derrick arm with a rope and basket at one end and a counterbalance of large stones tied to the other end.
When a gem-bearing stratum is reached each basketful of soil is placed to one side at the top of the shaft, to be washed and sorted. In some instances a horizontal shaft will be dug to follow the gem-bearing stratum, but as no wooden props or tunnel shores are used the length of these horizontal tunnels is limited by the courage and tenacity of the digger, not to mention his ability to breathe in the tomblike atmosphere. No ladders are provided in the vertical shaft, and entry and exit are effected by bracing the back and hands against one wall and the feet against the opposite side, at the same time exerting the body in a motion that would do credit to James Bond in tightest spot.
There is no natural supply of water for washing the extractions, so the miners pay for this to be brought from the nearby village by water-tank lorries. A small pond about ten feet in diameter and three feet deep is formed near the shaft and the baskets of soil are washed and broken up by members of the group sitting in the pond. As and when the gemstones are found, these are placed in small plastic bags around the perimeter of the pond.
This particular area produces a fair quantity of corundum, most of the crystals being in the form of repeated lamellar twinning. In this form some of the stones can be cut en cabochon to exhibit fine golden six-rayed stars on a dark brown to nearly black background, and on my visit I met Khun Saengroong, a local dealer and cutter, who had just bought a magnificent hexagonal lamellar crystal of star sapphire material weighing 1720 carats. This is of course a rare exception and the average size seldom exceeds 15 carats, and even then only very few of the stones will, when cut, show a well-centered star without the disfiguration of the prominent zone lines which are a feature of the stones from this mine.
The local ‘test’ for rough star sapphire material is to place a drop of water on the stone and to view it from an overhead single light source. In a suitable crystal the ‘star’ will show up clearly when the drop of water is placed in the right position. As it is to be expected, a very great proportion of these opaque corundum crystals show a very poor, or no, star-effect, and these fetch very low prices.
In quantity, the second main gem production of this area is green sapphire, followed by blue/green, yellow/green and more rarely fine blue and yellow sapphire. The hexagonal zoning is easily detected under the lens in a large majority of these stones.
Also associated with the corundum are pyrope garnet (R.I=1.745-1.750) and a fairly large quantity of opaque black stones which take a high polish and are sold both faceted and en cabochon as ‘Thai Jet’. Kenneth Parkinson took ten of these back to the U.K and has since written to tell me that seven of these have a S.G of between 4.1 and 4.2 and with a R.I just visible at the very end of the standard refractometer it seems fairly certain that they are black almandines. The other three stones proved to be black diopside (no star or cat’s eye) with a clear double refraction 1.68 – 1.71. Although this is slightly higher than the normal 1.67 – 1.70, Webster (Gems, 2nd Edition, page 264) notes that the R.I may rise when the material is so dark as to be virtually hedenbergite.
Many jewelers and gem dealers in Bangkok will inform their customers ‘These stones come from our own mine at Chantaburi’, but it is very doubtful whether any of them actually engage in mining themselves, as those who have taken a lease and employed people to dig for them have usually found that somehow their area seems to produce only low-grade stones. The best quality stones will find their way into the market, but not through the lease-holder. The local expression is ‘employ someone to dig and your stone will fly.’
Dealers and middlemen gather at a small group of wooden coffee shops at the fork of two roads leading into the mining area and it is here, in the late afternoon, that the miners bring their daily production for sale.
The existence of these sapphire mines and others in the area producing ruby and zircon, has created a flourishing cutting and setting center in the town of Chantaburi. The standard of work is high, and compared with western prices, cutting costs are very low. A skilled Thai lapidary will be paid about 20 pence for faceting and polishing a zircon of one carat. These low cutting costs have prompted many of the local dealers to import rough gem material for cutting in Thailand and eventual export to the major markets in Europe and the USA. When Kenneth Parkinson and I were in Chantaburi we were shown a parcel of fine blue sapphire crystals recently purchased in Australia. One could not help thinking of the expression ‘bringing coals to Newcastle’.
Although sapphire, ruby and zircon are the principal materials cut at Chantaburi, opal, emerald and other rough is imported for cutting. It is perhaps inevitable that half boules of synthetic corundum are to be seen in many of the gem cutting shops, and, although the majority of dealers will not offer synthetics as anything but what they are, one suspects that a few will be sorely tempted when selling to some of the gullible foreign tourists who are now starting to visit this area.
(via The Journal of Gemmology, Vol.13, No.8, October 1973) J A L Pavitt writes:
Thailand, or Siam as it was formerly named, is a well-known source of sapphire, ruby, star-sapphire and zircon and over the years the skill of Thai lapidaries has advanced to a very high degree, making Bangkok, the capital city, an important center for the supply of cut gemstones.
There are a number of gem mining localities in Thailand, many of them in remote areas, but the mines at Chantaburi (also known as Chantabun), 200 miles from Bangkok, can be reached by car in five and a half hours, and soon after our arrival in Thailand in 1971 my wife and I made our first visit to Khau Ploi Waen, or ‘Hill of the Sapphire Ring’, as this mining area at Chantaburi is named. I have since made further visits, the most recent in January 1973 with Mr Kenneth Parkinson during his two week visit to Thailand.
Chantaburi has a very special place in the history and culture of the Kingdom of Thailand. Situated near the coast, only thirty miles from the border with Cambodia, its inhabitants, although loyal and proud Thai nationals have ethnic origins connecting many of them with the diverse civilizations which existed thousands of years ago between the borders of China and the Mekong Delta. These origins are still evident in the customs, skills, religious and dialects to be found among the people of this fertile eastern region of the Kingdom.
It was at Chantaburi that King Taksin marshaled his forces after the fall of the ancient city of Ayuthaya, and finally defeated and drove out the Burmese invaders. Close to the sapphire mines one can see the rusting cannon and remains of the fortress of King Rama III (1787 – 1851).
The gem-bearing deposits at Khau Ploi Waen are about six miles south of the town of Chantaburi, near the village of Ban Kacha. Past records indicate that in 1850 the Shans and Burmese were extracting sapphires here and that in 1850 a British Company obtained a lease but failed to make a success of the venture. In 1919 the Siam Mining Act came into force and since then mining has been solely in the hands of Thai nationals.
The mining area is privately owned and has been cleared of primary growth and planted with rubber trees, although it is obvious that an income from rubber tapping is of minor importance. A lease to dig for gemstones over an area of one ‘rai’ (approx. 0.4 acre) for one year is granted by the landlords for a fee which may be as high as baht 300000 for high yield areas which have not previously been worked. A lease is usually shared by groups or families and there are said to be some 2000 people mining around Khau Ploi Waen.
The method of extracting the stones is very primitive, as are the tools—a pick, a spade and a rattan basket. A vertical shaft of about four feet in diameter is dug in the red/brown clay soil, in between the rubber trees. These vertical shafts sometimes go as far as thirty feet deep and each basketful of soil is lifted to the surface by a crude, but effective, crane arrangement consisting of two bamboo legs and a long bamboo derrick arm with a rope and basket at one end and a counterbalance of large stones tied to the other end.
When a gem-bearing stratum is reached each basketful of soil is placed to one side at the top of the shaft, to be washed and sorted. In some instances a horizontal shaft will be dug to follow the gem-bearing stratum, but as no wooden props or tunnel shores are used the length of these horizontal tunnels is limited by the courage and tenacity of the digger, not to mention his ability to breathe in the tomblike atmosphere. No ladders are provided in the vertical shaft, and entry and exit are effected by bracing the back and hands against one wall and the feet against the opposite side, at the same time exerting the body in a motion that would do credit to James Bond in tightest spot.
There is no natural supply of water for washing the extractions, so the miners pay for this to be brought from the nearby village by water-tank lorries. A small pond about ten feet in diameter and three feet deep is formed near the shaft and the baskets of soil are washed and broken up by members of the group sitting in the pond. As and when the gemstones are found, these are placed in small plastic bags around the perimeter of the pond.
This particular area produces a fair quantity of corundum, most of the crystals being in the form of repeated lamellar twinning. In this form some of the stones can be cut en cabochon to exhibit fine golden six-rayed stars on a dark brown to nearly black background, and on my visit I met Khun Saengroong, a local dealer and cutter, who had just bought a magnificent hexagonal lamellar crystal of star sapphire material weighing 1720 carats. This is of course a rare exception and the average size seldom exceeds 15 carats, and even then only very few of the stones will, when cut, show a well-centered star without the disfiguration of the prominent zone lines which are a feature of the stones from this mine.
The local ‘test’ for rough star sapphire material is to place a drop of water on the stone and to view it from an overhead single light source. In a suitable crystal the ‘star’ will show up clearly when the drop of water is placed in the right position. As it is to be expected, a very great proportion of these opaque corundum crystals show a very poor, or no, star-effect, and these fetch very low prices.
In quantity, the second main gem production of this area is green sapphire, followed by blue/green, yellow/green and more rarely fine blue and yellow sapphire. The hexagonal zoning is easily detected under the lens in a large majority of these stones.
Also associated with the corundum are pyrope garnet (R.I=1.745-1.750) and a fairly large quantity of opaque black stones which take a high polish and are sold both faceted and en cabochon as ‘Thai Jet’. Kenneth Parkinson took ten of these back to the U.K and has since written to tell me that seven of these have a S.G of between 4.1 and 4.2 and with a R.I just visible at the very end of the standard refractometer it seems fairly certain that they are black almandines. The other three stones proved to be black diopside (no star or cat’s eye) with a clear double refraction 1.68 – 1.71. Although this is slightly higher than the normal 1.67 – 1.70, Webster (Gems, 2nd Edition, page 264) notes that the R.I may rise when the material is so dark as to be virtually hedenbergite.
Many jewelers and gem dealers in Bangkok will inform their customers ‘These stones come from our own mine at Chantaburi’, but it is very doubtful whether any of them actually engage in mining themselves, as those who have taken a lease and employed people to dig for them have usually found that somehow their area seems to produce only low-grade stones. The best quality stones will find their way into the market, but not through the lease-holder. The local expression is ‘employ someone to dig and your stone will fly.’
Dealers and middlemen gather at a small group of wooden coffee shops at the fork of two roads leading into the mining area and it is here, in the late afternoon, that the miners bring their daily production for sale.
The existence of these sapphire mines and others in the area producing ruby and zircon, has created a flourishing cutting and setting center in the town of Chantaburi. The standard of work is high, and compared with western prices, cutting costs are very low. A skilled Thai lapidary will be paid about 20 pence for faceting and polishing a zircon of one carat. These low cutting costs have prompted many of the local dealers to import rough gem material for cutting in Thailand and eventual export to the major markets in Europe and the USA. When Kenneth Parkinson and I were in Chantaburi we were shown a parcel of fine blue sapphire crystals recently purchased in Australia. One could not help thinking of the expression ‘bringing coals to Newcastle’.
Although sapphire, ruby and zircon are the principal materials cut at Chantaburi, opal, emerald and other rough is imported for cutting. It is perhaps inevitable that half boules of synthetic corundum are to be seen in many of the gem cutting shops, and, although the majority of dealers will not offer synthetics as anything but what they are, one suspects that a few will be sorely tempted when selling to some of the gullible foreign tourists who are now starting to visit this area.
Gemmology On A Shoestring
(via The Journal of Gemmology, Vol.10, No.3, July 1966) B W Anderson writes:
Further simple tests
The tests so far suggested have involved only the use of lens and tongs. I am now going to suggest the use of a few very simple ‘extras’ which I feel can be included under our ‘shoestring’ limit, and which will undoubtedly extend quite considerably the scope and certainty of our gem identification. The first extra is the well-known Chelsea filter, which was developed by A Ross Popley from a formula worked out by C J Payne and myself in the early thirties. In knowledgeable hands, and properly used, the filter can be extremely useful. If used without any knowledge of how it functions, it can be quite misleading. Basically, it is a very efficient ‘dichromatic’ filter, transmitting only a narrow band of deep red light and a narrow band of yellow green. Thus, through the filter, a stone can only appear red, green, or a mixture of the two. Filters of this type were originally designed to distinguish between emeralds and pastes or doublets. Emerald, unlike most green stones, both transmits deep red light and emits fluorescent red light when it is brightly illuminated. To see the effect at its best, the stone should be held immediately under a good tungsten light and viewed through the filter held close to the eye. The snags in this simple use of the filter for emerald are that two other green stones, demantoid garnet and fluorspar, may show a reddish residual color when viewed through the filter, that synthetic emeralds appear an even more decisive red than natural emeralds, and that natural emeralds containing enough iron to damp its fluorescence and cause absorption in the deep red do not appear red through the filter. But in my opinion the warning given by the very intense red shown by Chatham synthetic emerald when viewed through the filter is a most useful indication, white its other uses in clearly distinguishing between aquamarine (green appearance) and synthetic blue spinel (orange red) between stained green chalcedony and chrysoprase, etc. serve to add to its value.
Next, quite another kind of filter: Polaroid. This astonishing invention of perhaps the most inventive of modern men, E H Land has placed polarized light, with all its peculiar and revealing properties, within the reach of everyone, and in a form far more compact and convenient than the old Nicol prism. A number of different formulae have been employed in producing the highly dichroic substances in plastic sheets which constitute Polaroid, but the effect in each case is essentially the same—that a ray of light which has passed through such a sheet is vibrating parallel to one direction only—that is, it is completely polarized. Such pieces of polarizing film are capable of far more valuable and fundamental used in the study of gemstones than any color filter can be, and fortunately the material is quite inexpensive; about four shillings per square inch, up to virtually any size required. The most favored type transmits 34% of incident white light, and two pieces of this in the ‘crossed’ position give virtually complete extinction.
One of the most obvious ways of using this material in gem testing is to mount two discs of polaroid in the ‘crossed’ position with a space between them enough to accommodate any gemstone, thereby forming that very sensitive instrument for the detection of double refraction known as the ‘polariscope’. A gadget of this kind can be easily home made, but there are some inexpensive types, carefully designed for convenience in use, which are commercially available. A useful pocket polariscope is one made by Rayner from a design of Dr E Rutland’s, while the same firm make an extremely convenient table model with a built-in light, which leaves ample room for large specimens, either dry or in a cell of suitable liquid; it can also easily accommodate massive pieces of jewelry, stones in necklaces, etc. can be examined, and both hands are free for manipulation.
A gemologist worth his salt will get much more information from such a polariscope than ‘four times light, four times dark—there a doubly refracting crystal’. He will learn to recognize the characteristic types of ‘strain birefringence’ shown by paste imitations (which often show a crude interference cross) by synthetic spinels, with their ‘tabby extinction’ patterns, by diamond, which is never truly isotropic in gem sizes, but shows brilliant interference colors, usually centered on the various points where tiny inclusions can be located, and so on. He will also learn to use a pocket lens to reveal interference figures, at least in the simpler cases, and the sight of a uniaxial figure through the table facet of a ruby or sapphire will give him fairly strong assurance that the stone is a natural one. The unique interference figure of quartz, with its hollow colored center can often provide a quick proof for this mineral. This is beautifully and easily seen in beads of rock crystal or crystal balls, in which the spherical shape makes the figure visible without the use of a lens to provide the ‘conoscope’ effect.
Polaroid can also be used to detect dichroism in gemstones. Two pieces can be set with vibrations at right angles to each other in a pair of old spectacle frames, and a specimen viewed in rapid alternation first with one eye and then the other, often showing a marked change in color, or narrow strips of Polaroid in alternating vibration directions can be counted on a disc of plain glass which can be mounted at one end of a short metal tube with a low power lens at the other. This forms an effective dichroscope for stones that are not too tiny: a dichroic stone viewed through the tube showing alternating stripes of different color or depth of color. Alternatively the Polaroid disc at the end of the tube can be cut into four sectors, the top and bottom sectors transmitting light vibrating, say, north and south, while the left and right hand sectors transmit only light which is vibrating east and west. In testing for dichroism it is best to use daylight reflected from a white surface if possible, and always one should turn both the specimen and the dichroscope tube before deciding on the strength of the dichroism—if there is any.
The next simple and inexpensive aids to gem testing that I want to recommend comprise liquids of various kinds, glass cells of suitable depth and diameter, a glass funnel and some filter papers. These can be used in a number of ways: to enable the color distribution and other internal features of rough or cut stones to be studied with ease: as a rapid test for the density of unmounted stones: and as a means of assessing the refractive index of unknown specimens.
A useful stock to begin with would be two ounces each of methylene iodide, bromoform and bromobenzene, and four ounces of monobromonapthalene, each in screw-top bottles of brown glass.
When stones are immersed in a liquid of similar refractive index the surface reflections and the effects of refraction are largely eliminated and one is able to ‘see into’ the specimens as easily as though they were parallel-sided plates. The ‘frosted’ effect of the surface of rough gem pebbles is also eliminated when they are immersed in a suitable liquid, and lapidaries are well advised to use this means of seeing the color distribution, flaws, etc. of rough gems to enable them to be cut to the best advantage.
Gemologists are familiar with the technique of placing a suspected ruby or sapphire in an immersion cell of liquid before examining it under the microscope, but they may not realize how helpful immersion may be for observations with the naked eye or with a lens. Sapphires in particular can usually be recognized as natural or as synthetic when immersed in bromonapthalene and viewed against a white background. Natural sapphires almost invariably show zones of color with rigidly straight edges, while synthetics slow the well-known curved swathes of color when observed in the correct direction.
A simple and effective means of illumination is to place the stone in its immersion cell on the base of another, inverted glass cell of rather larger size, and direct the light from a bench lamp on to the white blotting paper on which this stands.
For density tests a stone must of course be free from its setting. Granted this, there is no simpler or more decisive way of distinguishing, for instance, between chrysoberyl and quartz cat’s eye, between aquamarine and synthetic spinel, or topaz and yellow quartz, than to put the stone in question into a tube of methylene iodide and seeing whether it floats or sinks. On the whole it is advisable to keep your liquids as pure compounds rather than as mixtures, as in that way their densities and refractive indices remain constant, except for slight variations with temperature. A very useful mixture, however, is one of bromoform diluted with monobromonapthalene until a small clear quartz crystal remains suspended in it. So constant is quartz in its density that this will serve as a virtual identification liquid for any of the transparent quartz gems such as amethyst and citrine. But also it will serve to identify Chatham, Gilson, or Zerfass synthetic emeralds, since the density of these is almost identical to the 2.651 of quartz.
Using liquids as a guide to the refractive index of gemstones has much in common with their used in checking density. In both cases a quite crude test may be all that is required to resolve a doubt, and in both cases quite accurate results can be achieved if this is necessary by taking more time and refining one’s techniques. Even with mounted stones liquids can quickly give useful clues to refractive index. If the small diamonds in a cluster ring, for instance, are suspect, a clear decision can be given if the entire ring be immersed in methylene iodide and the stone viewed with a lens. If the stones are diamond the refractive index is so much higher than that of 1.74 of the liquid that the facets and edges will still appear sharp and clear, while synthetic white spinel and synthetic white sapphire will virtually disappear in this fluid. With loose stones, a very fair idea of their refractivity can be quite quickly and easily obtained by placing the stones table facet down in fair-sized glass cell and pouring in enough monobromonapthalene (R.I = 1.66) to just cove them completely. The cell should be placed on a sheet of white blotting paper and the stones viewed by the light of a single bulb some distance overhead. Those stones with an index higher than that of bromonapthalene will show a distinct dark rim round their periphery, as seen projected on the paper below, and the projection of the facet edges will appear white whereas with stones of lower refractive than the liquid a pale surrounding rim can be seen with the facet edges as dark lines. The degree to which the index of the stone is lower or higher than that of the liquid can be assessed with fair accuracy by noting the width of the dark or pale rim. Unlike the well-known “Becke’ methods for gauging whether an immersed grain is more or less refractive than the liquid, the procedure leaves no doubt at all in the observer’s mind about which has the higher index. A refinement of this simple test is to place the cell containing the immersed stones on a finely-ground glass sheet which is made to act as a bridge between two four-inch blocks of wood or still cardboard. A ‘handbag’ mirror of suitable size is placed at 45º under the cell, enabling the projection onto the glass sheet of the stones, to be seen in detail and in comfort. The effects seen are really very beautiful as well as revealing. If a permanent record is required, a contact photograph can be easily obtained in a dark room by placing the cell containing the stones over a piece of slow film and exposing for a few seconds to an overhead light. Those who are photographers can make use of the narrow beam of light from an enlarger stopped down to f22, and thus obtain very sharp and detailed photographs. Internal features of the stones, in particular color zoning, show up very clearly on such photographs, particularly where the liquid and stones of nearly the same index. I have found that the curved striae in synthetic corundums may be discerned in such photographs even if invisible under the microscope. For this, however, carefully filtered methylene iodide is necessary, and one must be lucky in hitting the right direction for showing the lines. I have only had time to give bare outline of these methods: but anyone seriously interested will find details, with diagrams and photographs, in my book ‘Gem Testing’.
I have included bromobenzene in my short list of useful liquids because this fairly pleasant and inexpensive liquid as a refractive index of 1.56. This makes it an ideal immersion liquid for the critical examination of emerald: it enables the thin rim of dark color to be seen at the edges and corners of the ‘Lechleitner’ type of synthetic emerald, in which a pale, faceted beryl is used as the ‘seed’ on which a thin crystalline layer of synthetic emerald is grown hydrothermally. Quite a few of these stones are now being used in mounted jewelry. The index of bromobenzene is also between that for synthetic emeralds of the Chatham, Gilson and Zerfass types and the indices found in natural emeralds. A good immersion contact photograph of synthetic and natural emeralds immersed in bromobenzene will reveal this.
Two pieces of advice I should like to add because I am so convinced of their importance for any budding gemologist. The first is to start a collection of gemstones, because the ability to compare the appearance and properties of an unknown stone with known samples is of inestimable value in testing. Even a collection of all available synthetics, doublets, pastes, etc. makes a most useful and interesting beginning. For genuine stones the ‘shoestring’ may only permit one to acquire only quite small specimens, or chipped or broken pieces, but one must realize that money spent on any fine specimen is not lost but invested, since the value of these is continuously increasing. The second piece of advice is to have at hand one or two reliable reference books. Two by Robert Webster stand out by reason of their accuracy and comprehensiveness. His ‘Gemologist’s Compendium’ contains all the necessary data gemstones in condensed form, and is very reasonably priced, while his two-volume work ‘Gems’, though expensive, contains such a wealth of information as to be well worth the money for any sizeable firm or jewelers or any serious student of the subject.
A trained gemologist can go a long way in gem identification by intelligent use of a good lens and few simple bits of apparatus, but I must repeat the warning that some of the problems confronting the trade today need more than this for their correct solution: they need all the facilities and skills of a specialized laboratory.
Further simple tests
The tests so far suggested have involved only the use of lens and tongs. I am now going to suggest the use of a few very simple ‘extras’ which I feel can be included under our ‘shoestring’ limit, and which will undoubtedly extend quite considerably the scope and certainty of our gem identification. The first extra is the well-known Chelsea filter, which was developed by A Ross Popley from a formula worked out by C J Payne and myself in the early thirties. In knowledgeable hands, and properly used, the filter can be extremely useful. If used without any knowledge of how it functions, it can be quite misleading. Basically, it is a very efficient ‘dichromatic’ filter, transmitting only a narrow band of deep red light and a narrow band of yellow green. Thus, through the filter, a stone can only appear red, green, or a mixture of the two. Filters of this type were originally designed to distinguish between emeralds and pastes or doublets. Emerald, unlike most green stones, both transmits deep red light and emits fluorescent red light when it is brightly illuminated. To see the effect at its best, the stone should be held immediately under a good tungsten light and viewed through the filter held close to the eye. The snags in this simple use of the filter for emerald are that two other green stones, demantoid garnet and fluorspar, may show a reddish residual color when viewed through the filter, that synthetic emeralds appear an even more decisive red than natural emeralds, and that natural emeralds containing enough iron to damp its fluorescence and cause absorption in the deep red do not appear red through the filter. But in my opinion the warning given by the very intense red shown by Chatham synthetic emerald when viewed through the filter is a most useful indication, white its other uses in clearly distinguishing between aquamarine (green appearance) and synthetic blue spinel (orange red) between stained green chalcedony and chrysoprase, etc. serve to add to its value.
Next, quite another kind of filter: Polaroid. This astonishing invention of perhaps the most inventive of modern men, E H Land has placed polarized light, with all its peculiar and revealing properties, within the reach of everyone, and in a form far more compact and convenient than the old Nicol prism. A number of different formulae have been employed in producing the highly dichroic substances in plastic sheets which constitute Polaroid, but the effect in each case is essentially the same—that a ray of light which has passed through such a sheet is vibrating parallel to one direction only—that is, it is completely polarized. Such pieces of polarizing film are capable of far more valuable and fundamental used in the study of gemstones than any color filter can be, and fortunately the material is quite inexpensive; about four shillings per square inch, up to virtually any size required. The most favored type transmits 34% of incident white light, and two pieces of this in the ‘crossed’ position give virtually complete extinction.
One of the most obvious ways of using this material in gem testing is to mount two discs of polaroid in the ‘crossed’ position with a space between them enough to accommodate any gemstone, thereby forming that very sensitive instrument for the detection of double refraction known as the ‘polariscope’. A gadget of this kind can be easily home made, but there are some inexpensive types, carefully designed for convenience in use, which are commercially available. A useful pocket polariscope is one made by Rayner from a design of Dr E Rutland’s, while the same firm make an extremely convenient table model with a built-in light, which leaves ample room for large specimens, either dry or in a cell of suitable liquid; it can also easily accommodate massive pieces of jewelry, stones in necklaces, etc. can be examined, and both hands are free for manipulation.
A gemologist worth his salt will get much more information from such a polariscope than ‘four times light, four times dark—there a doubly refracting crystal’. He will learn to recognize the characteristic types of ‘strain birefringence’ shown by paste imitations (which often show a crude interference cross) by synthetic spinels, with their ‘tabby extinction’ patterns, by diamond, which is never truly isotropic in gem sizes, but shows brilliant interference colors, usually centered on the various points where tiny inclusions can be located, and so on. He will also learn to use a pocket lens to reveal interference figures, at least in the simpler cases, and the sight of a uniaxial figure through the table facet of a ruby or sapphire will give him fairly strong assurance that the stone is a natural one. The unique interference figure of quartz, with its hollow colored center can often provide a quick proof for this mineral. This is beautifully and easily seen in beads of rock crystal or crystal balls, in which the spherical shape makes the figure visible without the use of a lens to provide the ‘conoscope’ effect.
Polaroid can also be used to detect dichroism in gemstones. Two pieces can be set with vibrations at right angles to each other in a pair of old spectacle frames, and a specimen viewed in rapid alternation first with one eye and then the other, often showing a marked change in color, or narrow strips of Polaroid in alternating vibration directions can be counted on a disc of plain glass which can be mounted at one end of a short metal tube with a low power lens at the other. This forms an effective dichroscope for stones that are not too tiny: a dichroic stone viewed through the tube showing alternating stripes of different color or depth of color. Alternatively the Polaroid disc at the end of the tube can be cut into four sectors, the top and bottom sectors transmitting light vibrating, say, north and south, while the left and right hand sectors transmit only light which is vibrating east and west. In testing for dichroism it is best to use daylight reflected from a white surface if possible, and always one should turn both the specimen and the dichroscope tube before deciding on the strength of the dichroism—if there is any.
The next simple and inexpensive aids to gem testing that I want to recommend comprise liquids of various kinds, glass cells of suitable depth and diameter, a glass funnel and some filter papers. These can be used in a number of ways: to enable the color distribution and other internal features of rough or cut stones to be studied with ease: as a rapid test for the density of unmounted stones: and as a means of assessing the refractive index of unknown specimens.
A useful stock to begin with would be two ounces each of methylene iodide, bromoform and bromobenzene, and four ounces of monobromonapthalene, each in screw-top bottles of brown glass.
When stones are immersed in a liquid of similar refractive index the surface reflections and the effects of refraction are largely eliminated and one is able to ‘see into’ the specimens as easily as though they were parallel-sided plates. The ‘frosted’ effect of the surface of rough gem pebbles is also eliminated when they are immersed in a suitable liquid, and lapidaries are well advised to use this means of seeing the color distribution, flaws, etc. of rough gems to enable them to be cut to the best advantage.
Gemologists are familiar with the technique of placing a suspected ruby or sapphire in an immersion cell of liquid before examining it under the microscope, but they may not realize how helpful immersion may be for observations with the naked eye or with a lens. Sapphires in particular can usually be recognized as natural or as synthetic when immersed in bromonapthalene and viewed against a white background. Natural sapphires almost invariably show zones of color with rigidly straight edges, while synthetics slow the well-known curved swathes of color when observed in the correct direction.
A simple and effective means of illumination is to place the stone in its immersion cell on the base of another, inverted glass cell of rather larger size, and direct the light from a bench lamp on to the white blotting paper on which this stands.
For density tests a stone must of course be free from its setting. Granted this, there is no simpler or more decisive way of distinguishing, for instance, between chrysoberyl and quartz cat’s eye, between aquamarine and synthetic spinel, or topaz and yellow quartz, than to put the stone in question into a tube of methylene iodide and seeing whether it floats or sinks. On the whole it is advisable to keep your liquids as pure compounds rather than as mixtures, as in that way their densities and refractive indices remain constant, except for slight variations with temperature. A very useful mixture, however, is one of bromoform diluted with monobromonapthalene until a small clear quartz crystal remains suspended in it. So constant is quartz in its density that this will serve as a virtual identification liquid for any of the transparent quartz gems such as amethyst and citrine. But also it will serve to identify Chatham, Gilson, or Zerfass synthetic emeralds, since the density of these is almost identical to the 2.651 of quartz.
Using liquids as a guide to the refractive index of gemstones has much in common with their used in checking density. In both cases a quite crude test may be all that is required to resolve a doubt, and in both cases quite accurate results can be achieved if this is necessary by taking more time and refining one’s techniques. Even with mounted stones liquids can quickly give useful clues to refractive index. If the small diamonds in a cluster ring, for instance, are suspect, a clear decision can be given if the entire ring be immersed in methylene iodide and the stone viewed with a lens. If the stones are diamond the refractive index is so much higher than that of 1.74 of the liquid that the facets and edges will still appear sharp and clear, while synthetic white spinel and synthetic white sapphire will virtually disappear in this fluid. With loose stones, a very fair idea of their refractivity can be quite quickly and easily obtained by placing the stones table facet down in fair-sized glass cell and pouring in enough monobromonapthalene (R.I = 1.66) to just cove them completely. The cell should be placed on a sheet of white blotting paper and the stones viewed by the light of a single bulb some distance overhead. Those stones with an index higher than that of bromonapthalene will show a distinct dark rim round their periphery, as seen projected on the paper below, and the projection of the facet edges will appear white whereas with stones of lower refractive than the liquid a pale surrounding rim can be seen with the facet edges as dark lines. The degree to which the index of the stone is lower or higher than that of the liquid can be assessed with fair accuracy by noting the width of the dark or pale rim. Unlike the well-known “Becke’ methods for gauging whether an immersed grain is more or less refractive than the liquid, the procedure leaves no doubt at all in the observer’s mind about which has the higher index. A refinement of this simple test is to place the cell containing the immersed stones on a finely-ground glass sheet which is made to act as a bridge between two four-inch blocks of wood or still cardboard. A ‘handbag’ mirror of suitable size is placed at 45º under the cell, enabling the projection onto the glass sheet of the stones, to be seen in detail and in comfort. The effects seen are really very beautiful as well as revealing. If a permanent record is required, a contact photograph can be easily obtained in a dark room by placing the cell containing the stones over a piece of slow film and exposing for a few seconds to an overhead light. Those who are photographers can make use of the narrow beam of light from an enlarger stopped down to f22, and thus obtain very sharp and detailed photographs. Internal features of the stones, in particular color zoning, show up very clearly on such photographs, particularly where the liquid and stones of nearly the same index. I have found that the curved striae in synthetic corundums may be discerned in such photographs even if invisible under the microscope. For this, however, carefully filtered methylene iodide is necessary, and one must be lucky in hitting the right direction for showing the lines. I have only had time to give bare outline of these methods: but anyone seriously interested will find details, with diagrams and photographs, in my book ‘Gem Testing’.
I have included bromobenzene in my short list of useful liquids because this fairly pleasant and inexpensive liquid as a refractive index of 1.56. This makes it an ideal immersion liquid for the critical examination of emerald: it enables the thin rim of dark color to be seen at the edges and corners of the ‘Lechleitner’ type of synthetic emerald, in which a pale, faceted beryl is used as the ‘seed’ on which a thin crystalline layer of synthetic emerald is grown hydrothermally. Quite a few of these stones are now being used in mounted jewelry. The index of bromobenzene is also between that for synthetic emeralds of the Chatham, Gilson and Zerfass types and the indices found in natural emeralds. A good immersion contact photograph of synthetic and natural emeralds immersed in bromobenzene will reveal this.
Two pieces of advice I should like to add because I am so convinced of their importance for any budding gemologist. The first is to start a collection of gemstones, because the ability to compare the appearance and properties of an unknown stone with known samples is of inestimable value in testing. Even a collection of all available synthetics, doublets, pastes, etc. makes a most useful and interesting beginning. For genuine stones the ‘shoestring’ may only permit one to acquire only quite small specimens, or chipped or broken pieces, but one must realize that money spent on any fine specimen is not lost but invested, since the value of these is continuously increasing. The second piece of advice is to have at hand one or two reliable reference books. Two by Robert Webster stand out by reason of their accuracy and comprehensiveness. His ‘Gemologist’s Compendium’ contains all the necessary data gemstones in condensed form, and is very reasonably priced, while his two-volume work ‘Gems’, though expensive, contains such a wealth of information as to be well worth the money for any sizeable firm or jewelers or any serious student of the subject.
A trained gemologist can go a long way in gem identification by intelligent use of a good lens and few simple bits of apparatus, but I must repeat the warning that some of the problems confronting the trade today need more than this for their correct solution: they need all the facilities and skills of a specialized laboratory.
Sunday, July 08, 2007
Benitoite
Chemistry: Barium titanium silicate
Crystal system: Trigonal; crystal class ditrigonal bipyramidal; commonly as trigonal bipyramids.
Color: Transparent to translucent; blue (most common), violet blue, colorless, pink (rare).
Hardness: 6.5
Cleavage: None; Fracture: conchoidal.
Specific gravity: 3.65
Refractive index: 1.75 – 1.80; Uniaxial positive; 0.047; strong doubling.
Luster: Vitreous – sub-adamantine.
Dispersion: High (masked by body color).
Dichroism: Strong (blue and colorless).
Occurrence: San Benito County, California, U.S.A.
Notes
Discovered in 1906; Collectors stone; Looks like sapphire, but pronounced DR, dichroism and high dispersion, luminescence, and lower SG help in separation; bright blue in short wave; faceted, usually round brilliants to display dispersion.
Crystal system: Trigonal; crystal class ditrigonal bipyramidal; commonly as trigonal bipyramids.
Color: Transparent to translucent; blue (most common), violet blue, colorless, pink (rare).
Hardness: 6.5
Cleavage: None; Fracture: conchoidal.
Specific gravity: 3.65
Refractive index: 1.75 – 1.80; Uniaxial positive; 0.047; strong doubling.
Luster: Vitreous – sub-adamantine.
Dispersion: High (masked by body color).
Dichroism: Strong (blue and colorless).
Occurrence: San Benito County, California, U.S.A.
Notes
Discovered in 1906; Collectors stone; Looks like sapphire, but pronounced DR, dichroism and high dispersion, luminescence, and lower SG help in separation; bright blue in short wave; faceted, usually round brilliants to display dispersion.
U.S. Government Watchdog Demands Better Governmental Controls Over Kimberley Process
Chaim Even-Zohar writes about the GAO, the U.S governmental watchdog + its report to the U.S Congress on Kimberly Process Certification Scheme (KPCS) + other viewpoints @ http://www.idexonline.com/portal_FullEditorial.asp?TextSearch=&KeyMatch=0&id=26271
A Further Note On Diamonds, Real And Imitation, In The Roman Period
(via The Journal of Gemmology, Vol.13, No.8, October 1973) J M Ogden writes:
Since the brief note on Roman imitation diamonds by the writer was published in the Journal of Gemmology two fine Roman rings, both set with interesting stones have been available for study. The first has an attractive openwork-sided setting in which is set an octahedral stone. This stone was at first glance taken to a rock crystal of the type considered by the writer to be a Roman imitation of a natural diamond crystal. Closer inspection of the stone however revealed the typical surface decomposition characteristics of glass and the stone was, in fact, a yellowish white glass (the term paste would be wrong here, as technically this should only refer to those glasses with high refractive index and brilliance). The writer knows of other instances of rings set with glass octahedral, and these, like the rock crystals, might be taken to be imitations of diamond crystals. It might be argued that any reasonably knowledgeable Roman could have told glass from the invincible diamond, but one would expect that these copies of diamond crystals were more in the nature of moral frauds; in other words they would have been worn by those to whom the diamond was, for reasons of economy or rank out of reach. A similar state of affairs can be seen earlier in the Roman period when only free-born citizens were allowed to wear gold rings; slaves and others made do with wearing gilt bronze rings.
The second ring is extremely interesting and possibly even unique, as it is set with a brown diamond. This stone, larger than any other Roman diamond known to the writer, is in the form of rough natural twin octahedral. Alec Farn of the Gem Testing Laboratory very kindly examined and tested this stone and found it to be a brown-series diamond: two lines, at 4980 Angstrom, were visible in the spectrum, and there was a blue fluorescence under X-rays. The weight of the stone was difficult to gauge, but it must have been about 7 carats. The majority of the Roman diamonds known to the writer do not have recorded weights, but they generally would seem to weigh under a carat. This large stone under discussion was by no means obviously a diamond from color or appearance, except to one versed in crystallography; so other stones of a similar nature might exist, unrecognized, in museum or private collections. In its recent history the stone in this ring has been described in a multitude of ways, most recently as ‘Topaz’. This fine ring is of a similar type to the first ring mentioned above, although it is sturdier and its size would indicate that it was definitely a man’s ring. Both these rings were originally in the collection of Count Henri de Clercq Boisgelin, a well-known collector whose ancient jewelry included some of the finest specimens known. There is no cause to doubt that both these rings are genuine, and that they date from the late Roman period (c. 3rd - 4th century A.D). Close examination by the writer revealed no evidence that the stones were not originals: indeed the ring holding the diamond had quite obviously been made for that stone and none other. The coloration, surface appearance under strong magnification and the general ‘feel’ of the gold in both cases would show that the settings were as old as supposed.
No provenance is recorded for either of these rings, though it would seem likely that they were made in Italy or in one of the Eastern Roman centers such as Asia Minor or Egypt. The exact area of origin for the diamond is not known, but it would be likely that it was traded ‘loose’ from India, possibly via Alexandria.
Since the brief note on Roman imitation diamonds by the writer was published in the Journal of Gemmology two fine Roman rings, both set with interesting stones have been available for study. The first has an attractive openwork-sided setting in which is set an octahedral stone. This stone was at first glance taken to a rock crystal of the type considered by the writer to be a Roman imitation of a natural diamond crystal. Closer inspection of the stone however revealed the typical surface decomposition characteristics of glass and the stone was, in fact, a yellowish white glass (the term paste would be wrong here, as technically this should only refer to those glasses with high refractive index and brilliance). The writer knows of other instances of rings set with glass octahedral, and these, like the rock crystals, might be taken to be imitations of diamond crystals. It might be argued that any reasonably knowledgeable Roman could have told glass from the invincible diamond, but one would expect that these copies of diamond crystals were more in the nature of moral frauds; in other words they would have been worn by those to whom the diamond was, for reasons of economy or rank out of reach. A similar state of affairs can be seen earlier in the Roman period when only free-born citizens were allowed to wear gold rings; slaves and others made do with wearing gilt bronze rings.
The second ring is extremely interesting and possibly even unique, as it is set with a brown diamond. This stone, larger than any other Roman diamond known to the writer, is in the form of rough natural twin octahedral. Alec Farn of the Gem Testing Laboratory very kindly examined and tested this stone and found it to be a brown-series diamond: two lines, at 4980 Angstrom, were visible in the spectrum, and there was a blue fluorescence under X-rays. The weight of the stone was difficult to gauge, but it must have been about 7 carats. The majority of the Roman diamonds known to the writer do not have recorded weights, but they generally would seem to weigh under a carat. This large stone under discussion was by no means obviously a diamond from color or appearance, except to one versed in crystallography; so other stones of a similar nature might exist, unrecognized, in museum or private collections. In its recent history the stone in this ring has been described in a multitude of ways, most recently as ‘Topaz’. This fine ring is of a similar type to the first ring mentioned above, although it is sturdier and its size would indicate that it was definitely a man’s ring. Both these rings were originally in the collection of Count Henri de Clercq Boisgelin, a well-known collector whose ancient jewelry included some of the finest specimens known. There is no cause to doubt that both these rings are genuine, and that they date from the late Roman period (c. 3rd - 4th century A.D). Close examination by the writer revealed no evidence that the stones were not originals: indeed the ring holding the diamond had quite obviously been made for that stone and none other. The coloration, surface appearance under strong magnification and the general ‘feel’ of the gold in both cases would show that the settings were as old as supposed.
No provenance is recorded for either of these rings, though it would seem likely that they were made in Italy or in one of the Eastern Roman centers such as Asia Minor or Egypt. The exact area of origin for the diamond is not known, but it would be likely that it was traded ‘loose’ from India, possibly via Alexandria.
Gemmology On A Shoestring
(via The Journal of Gemmology, Vol.10, No.3, July 1966) B W Anderson writes:
Hardness
Hardness as a test has always been considered taboo amongst gemologist, partly because of the danger it implies of damaging the specimen tested, and partly because of its inexactness compared with refractive index or density determinations. But hardness has a marked influence on the degree of polish that a stone can take and maintain and thus affects the appearance of a stone. The sharp facet edges in diamond, for instance, help one to distinguish it from strontium titanate, where the edges often have an almost molded appearance. It is as well to realize that hard stones such as sapphire or even diamond may show an astonishing degree of wear, and one should be careful to avoid jumping to conclusions on this evidence alone. Since the hardness of diamond is unique, a careful trial with an edge of a suspected diamond on a piece of synthetic corundum is sometimes justified. If the specimen ‘bites’ on the corundum and leaves a definite mark, there is nothing else but diamond that it can be. Before the test is done, the corundum surface should be examined with a lens to ensure that no scratches are already there on the part that is to be used; and any mark made by the diamond should be rubbed with the finger and examined with a lens to ensure that it really is a scratch. With jade and the jade-like minerals gentle trials with a knife blade or needle point may yield valuable information, but should only be used where other tests fail, and when one can be sure that no damage results to the specimen. One should also recognize that there may be considerable variations in the hardness of such materials.
Density
Before the coming of the jeweler’s refractometer devised by the late Dr Herbert Smith, tests for specific gravity (density) were the only accurate means of determining the nature of any unmounted gemstone. It remains a thoroughly useful test for any stone free from its setting. Every gemologist knows that a simple trial in a heavy liquid will distinguish at once between yellow quartz and true topaz, or between quartz or chrysoberyl cat’s eyes. To make these distinctions by the ‘feel’ or ‘heft’ of the stone in your hand is a decidedly tricky business, but worth practicing. Even when strung a necklace, the extreme ‘lightness’ of amber can be noticeable, when compared with bakelite or other synthetic resins. The judgment of the weight of a stone in relation to its ‘spread’ is, of course closely bound up with a knowledge of its specific gravity, and here again the gemologist scores.
Cleavage
Where a stone has a marked cleavage, traces of this can often be noticed as flaws or incipient flaws within the stone or on the surface, where any nicks or chips may be seen to have flat sides instead of curved surfaces as in a conchoidal fracture. Cleavage nicks can often be detected round the girdle of a brilliant cut diamond, especially if the stone had been removed from a setting. This adds one more to the many revealing signs that one can find when examining a diamond.
Surface structures
This is rather a comprehensive heading, and can be used to cover such things as the traces of untouched crystal surface (naturals) that can often be detected on the girdle of a cut diamond; similar structures on the rear facets (really crystal faces) of a Lechleitner synthetic emerald, where the overgrowth is purposely left to enhance the color; the ‘flame’ pattern which is so completely distinctive for pink (conch) pearl, and so different from the grained structure of coral; the ‘engine-turned’ pattern on the surface of ivory; the dimpled surface of the fine jadeite; the demarcation line (nearly always above the girdle) marked by a sharp change in luster, when the surface of a garnet-topped doublet is examined in reflected light; the short, parallel crack-like markings (fire marks) due to careless cutting, seen only in corundum, more particularly in synthetic ruby or sapphire; and so on. A complete list of surface signs would be a very long one.
Internal structures
Internal structures or ‘inclusions’ should not really have come so late in the batting order, since such features are often of enormous help in identifying different gemstones and in distinguishing natural stones from their synthetic counterparts. But to study inclusions in their full beauty and detail one undoubtedly needs to examine them under a microscope—preferably a binocular microscope, and immersed in a cell of suitable fluid. Even with a pocket lens some inclusions are completely distinctive: for instance, the ‘horsetail’ inclusions of asbestos fibres which are almost invariably to be seen in demantoid garnet, and the ‘silk’ which is so typical a feature of Burma ruby. In both these cases of course the color and appearance of the stone will already have put you on the right track. The list of such ‘deadsure’ identifications by inclusions I not a very long one, however, except at the gifted hands and eyes of a master of the subject such as Dr Edward Gubelin. One should, however, be certain of an amethyst which shows the curious ‘tiger-stripe’ inclusions; of ‘goldstone’ (aventurine glass) with its glittering triangles of included copper; of a paste when it shows a typical elliptical bubble or so and of a doublet when a layer of bubbles can be seen at the surface where garnet meets the glass. Hessonite garnet, of course, is usually easy to detect with its crowded inclusion-picture of diopside crystals in a treacly golden brown setting. The curved lines in synthetic ruby may be too finely spaced for a lens to detect, but in sapphire the broader curved swathes of color are often more visible to the lens than under the microscope. The stone should be viewed against the white background of a sheet of clean paper or blotting paper, and turned in different directions until the right angle for viewing is found. Immersion in liquid will often help here (I am jumping ahead a little) and will also reveal the straight-sided bands of color so typical of natural sapphire. The ‘feel’ of a stone and its ‘coldness to the touch’ may also on occasion provide evidence of its nature.
Gemmology On A Shoestring (continued)
Hardness
Hardness as a test has always been considered taboo amongst gemologist, partly because of the danger it implies of damaging the specimen tested, and partly because of its inexactness compared with refractive index or density determinations. But hardness has a marked influence on the degree of polish that a stone can take and maintain and thus affects the appearance of a stone. The sharp facet edges in diamond, for instance, help one to distinguish it from strontium titanate, where the edges often have an almost molded appearance. It is as well to realize that hard stones such as sapphire or even diamond may show an astonishing degree of wear, and one should be careful to avoid jumping to conclusions on this evidence alone. Since the hardness of diamond is unique, a careful trial with an edge of a suspected diamond on a piece of synthetic corundum is sometimes justified. If the specimen ‘bites’ on the corundum and leaves a definite mark, there is nothing else but diamond that it can be. Before the test is done, the corundum surface should be examined with a lens to ensure that no scratches are already there on the part that is to be used; and any mark made by the diamond should be rubbed with the finger and examined with a lens to ensure that it really is a scratch. With jade and the jade-like minerals gentle trials with a knife blade or needle point may yield valuable information, but should only be used where other tests fail, and when one can be sure that no damage results to the specimen. One should also recognize that there may be considerable variations in the hardness of such materials.
Density
Before the coming of the jeweler’s refractometer devised by the late Dr Herbert Smith, tests for specific gravity (density) were the only accurate means of determining the nature of any unmounted gemstone. It remains a thoroughly useful test for any stone free from its setting. Every gemologist knows that a simple trial in a heavy liquid will distinguish at once between yellow quartz and true topaz, or between quartz or chrysoberyl cat’s eyes. To make these distinctions by the ‘feel’ or ‘heft’ of the stone in your hand is a decidedly tricky business, but worth practicing. Even when strung a necklace, the extreme ‘lightness’ of amber can be noticeable, when compared with bakelite or other synthetic resins. The judgment of the weight of a stone in relation to its ‘spread’ is, of course closely bound up with a knowledge of its specific gravity, and here again the gemologist scores.
Cleavage
Where a stone has a marked cleavage, traces of this can often be noticed as flaws or incipient flaws within the stone or on the surface, where any nicks or chips may be seen to have flat sides instead of curved surfaces as in a conchoidal fracture. Cleavage nicks can often be detected round the girdle of a brilliant cut diamond, especially if the stone had been removed from a setting. This adds one more to the many revealing signs that one can find when examining a diamond.
Surface structures
This is rather a comprehensive heading, and can be used to cover such things as the traces of untouched crystal surface (naturals) that can often be detected on the girdle of a cut diamond; similar structures on the rear facets (really crystal faces) of a Lechleitner synthetic emerald, where the overgrowth is purposely left to enhance the color; the ‘flame’ pattern which is so completely distinctive for pink (conch) pearl, and so different from the grained structure of coral; the ‘engine-turned’ pattern on the surface of ivory; the dimpled surface of the fine jadeite; the demarcation line (nearly always above the girdle) marked by a sharp change in luster, when the surface of a garnet-topped doublet is examined in reflected light; the short, parallel crack-like markings (fire marks) due to careless cutting, seen only in corundum, more particularly in synthetic ruby or sapphire; and so on. A complete list of surface signs would be a very long one.
Internal structures
Internal structures or ‘inclusions’ should not really have come so late in the batting order, since such features are often of enormous help in identifying different gemstones and in distinguishing natural stones from their synthetic counterparts. But to study inclusions in their full beauty and detail one undoubtedly needs to examine them under a microscope—preferably a binocular microscope, and immersed in a cell of suitable fluid. Even with a pocket lens some inclusions are completely distinctive: for instance, the ‘horsetail’ inclusions of asbestos fibres which are almost invariably to be seen in demantoid garnet, and the ‘silk’ which is so typical a feature of Burma ruby. In both these cases of course the color and appearance of the stone will already have put you on the right track. The list of such ‘deadsure’ identifications by inclusions I not a very long one, however, except at the gifted hands and eyes of a master of the subject such as Dr Edward Gubelin. One should, however, be certain of an amethyst which shows the curious ‘tiger-stripe’ inclusions; of ‘goldstone’ (aventurine glass) with its glittering triangles of included copper; of a paste when it shows a typical elliptical bubble or so and of a doublet when a layer of bubbles can be seen at the surface where garnet meets the glass. Hessonite garnet, of course, is usually easy to detect with its crowded inclusion-picture of diopside crystals in a treacly golden brown setting. The curved lines in synthetic ruby may be too finely spaced for a lens to detect, but in sapphire the broader curved swathes of color are often more visible to the lens than under the microscope. The stone should be viewed against the white background of a sheet of clean paper or blotting paper, and turned in different directions until the right angle for viewing is found. Immersion in liquid will often help here (I am jumping ahead a little) and will also reveal the straight-sided bands of color so typical of natural sapphire. The ‘feel’ of a stone and its ‘coldness to the touch’ may also on occasion provide evidence of its nature.
Gemmology On A Shoestring (continued)
Barytes
Chemistry: Barium sulphate
Crystal system: Orthorhombic; crystals often tabular; massive & stalagmatic form; rosette aggregate form.
Color: Transparent to opaque; colorless, blue, yellow, red, brown, green; massive white.
Hardness: 3
Cleavage: Perfect; in 3 directions, brittle; Fracture: uneven
Specific gravity: 4.3 – 4.6
Refractive index: 1.636 – 1.648; Biaxial positive; 0.012
Luster: Vitreous
Occurrence: Worldwide; Canada, USA, England, Germany, Spain.
Notes
Barytes is also called Barite (or Heavy Spar); massive white may resemble marble; some shows stalagmatic formation; crystal aggregates in the form of rosettes is often known as ‘desert roses’; fluorescent specimens may show faint blue/green colors; usually cut for collectors.
Crystal system: Orthorhombic; crystals often tabular; massive & stalagmatic form; rosette aggregate form.
Color: Transparent to opaque; colorless, blue, yellow, red, brown, green; massive white.
Hardness: 3
Cleavage: Perfect; in 3 directions, brittle; Fracture: uneven
Specific gravity: 4.3 – 4.6
Refractive index: 1.636 – 1.648; Biaxial positive; 0.012
Luster: Vitreous
Occurrence: Worldwide; Canada, USA, England, Germany, Spain.
Notes
Barytes is also called Barite (or Heavy Spar); massive white may resemble marble; some shows stalagmatic formation; crystal aggregates in the form of rosettes is often known as ‘desert roses’; fluorescent specimens may show faint blue/green colors; usually cut for collectors.
Saturday, July 07, 2007
Swarm Theory
The concept does makes sense in the gem and jewelry business. There is a link, and the behavioral pattern of the dealers, jewelers and consumers in the gem and jewelry sector are no different from ants, bees + other group (s) mentioned in the article. Though strange, you will have to 'see through' to understand the importance of swarm behavior.
Peter Miller writes about swarm intelligence + insights that can help humans manage complex systems + the complex behavior of a group + other viewpoints @ http://www7.nationalgeographic.com/ngm/0707/feature5/
Peter Miller writes about swarm intelligence + insights that can help humans manage complex systems + the complex behavior of a group + other viewpoints @ http://www7.nationalgeographic.com/ngm/0707/feature5/
Restructured DTC to Focus Solely on Rough Distribution as Core Business
Chaim Even-Zohar writes about modifications in the Diamond Trading Company’s (DTC) Sightholder selection process + the impact on sightholders + other viewpoints @ http://www.idexonline.com/portal_FullEditorial.asp
For Gemology Students
Dr Edward Gubelin is an inspiring icon (forever). He explains in his usual colorful tone how to connect gemology with other faculties of science (s) + to act with a sense of responsibility + gemology without conscience is the undoing of one's soul + to be honest and always tell the truth.
Dr Edward Gubelin's Address
In his address, following the presentation of awards to the Gemmological Association of Great Britain at Goldsmith’s Hall on 25th November, 1974, including candidates from many different parts of the world, Dr Edward Gubelin said:
What is happening on our planet today? I do not mean the belligerent tensions in the near East nor the failure to adopt a common energy policy nor the worldwide monetary crisis—no, what happens in this world as an entity, what happens at the present for the first time uniquely and so thoroughly that it will be remembered in the centuries to come, just a we still acknowledge and appreciate today the invention of the wheel, of the alphabet, the development of the great religions of the world, or from a geological point of view the folding up of the Alps, as an outstanding and irrevocable phenomenon. Well, what is happening in front of our eyes today? It is a tremendous and in its kind certainly a unique metamorphosis, which could at best compare with the change which mankind underwent during the dark ages and then again at the beginning of the Renaissance. The world happens to be in the midst of a fundamental change of structure with biological, physiological, sociological and even theological effects, and these are of such profundity that we cannot escape them.
To a certain extent we have been experiencing drastic changes also in our profession. Until recently, our idea of sales promotion moved along perspectives which had already been fixed in medieval times and which were almost exclusively limited to the mere action of selling, and best to a successful sales talk, while today after a short time of transition (calculating just a few years) great value is being placed in an extensive professional erudition, profound psychology, sound argumentation and efficient advice. While previously the old Roman warning Caveat Emptor, which originated from distrust, alerted the buyer to be careful, it now has the meaning that the client wishes to be well informed and accurately advised about the goods he is interested in purchasing. This desire may only be fulfilled by the salesman if he masters a fundamental professional knowledge. Science reigns today over all sequences of our life, medicine a well as commerce, production as well as communication, and the last consumer wishes to share in this professional science.
It is the aim of the gemological courses, which you have so successfully completed, to offer this specialized knowledge which will give you greater self-assurance and consequently increase well founded trust to assist your clients in such a way as to justify the confidence they place in your hands. The relatively broad spectrum of knowledge taught in the condensed form of, say, 25 or 30 assignments distributed over two courses challenged your capability to understand connexions and relationships which exist between different disciplines of the science of nature as well as between different properties of gemstones. The capacity of thinking in relationships and coordinations as well as the readiness to engage yourselves and to take responsibility and to accept solidarity should, apart from your technical achievement, be the human or spiritual benefit of your gemological study. In this sense, I wish to congratulate your most cordially on your successful attainment, which is the well deserved result of your perseverance and brave sacrifice during two years of intensive study. Not only your personal interest in gemology has led you to this award but also your thirst for knowledge and education, that marvelous, growing, aching process, whereby the mind develops into a usable instrument with a collection of proved experiences from which to function.
Some of you may consider the diploma examination as the climax of your gemological studies. Yet, may I bring to mind that this is rather the first ‘rung of the ladder’—that you have merely just crossed the threshold of a space spreading before you with no visible horizon, and the heady sensation you may feel now is only the beginning of further studies combined with unexpected experiences which perhaps are more closely linked with your practical everyday life in future. Therefore I recommend you to remain abreast of future developments by joining the advanced post diploma courses and subscribing to gemological periodicals.
Your diploma should not mislead you to consider yourselves as infallible experts. Your status quo is comparable to the situation of a young B.Sc or Ph.D who has just received his academic title, which does not attest him yet as a fully fledged scientist but merely that he has learnt to think and act independently and—as is to be hoped—with a sense of responsibility.
Among the resources offered to the modern science of nature gemology assumes a prominent place. Unfortunately it was considered a superfluous appendage and hardly acknowledged for almost a generation, and gemological publications only appeared as foot notes to mineralogical literature. Yet, indeed, as an independent basis, gemology has often supplied mineralogy with fundamental data and proved to be of invaluable assistance. Gemology was lacking professionalism for a long time and for far too long gemology was merely a trade accessory. Gemological degrees at present are still no more than school degrees, either rewarded by trade associations or by private institutes affiliated with the trade. An academic degree course would help in upgrading the profession’s standing similarly as university training would facilitate gemology and gemologists to meet the increasing technology and standard of investigation.
However, thanks to numerous outstanding achievements in highly scientific gemological research, today gemology is fully recognized as a science. As a matter of fact, gemology is today rightly entitled to claim the merit of having essentially contributed towards the astonishing progress of mineralogical research. The endeavor to expand as far as possible the boundaries within which may be possible, is a central motive of technical and scientific development. It is the same force which led our progenitors to master the use of fire and which drives us today to investigate outer space without knowing where this may lead us to. This intense desire of mankind to question all boundaries again and again is already grappled in the Genesis of the Old Testament by the words ‘Conquer the Earth with all that is within’ and thus deprived of any further argumentation. However, if man conquers the Earth, then he must corroborate by his mental disposition as well as by his moral conduct that he is indeed legitimized for this role—not only a scientist but also in his quality as a human being.
By this I mean to emphasize that we have a right to profit from our knowledge to our own personal advantage, yet never to use it to the harm of others. A French philosopher expressed this thought with the following word: ‘Science sans conscience n’est que ruine de l’ame’—science without conscience is the undoing of one’s soul. Scientific research means searching for the truth. Consequently, we are obliged to be honest and always tell the truth, and if we happen to make a mistake we should summon the courage to admit it.
Irrevocable laws do not only exist in the field of the sciences of nature but also in the sphere of human life and coexistence. In this connexion I may refer to the problematics of liberty and restraint, to all the tensions which occur because man is a personality who must develop in freedom, yet according to the laws of nature he is also a social being, who can only completely unfold himself in a society. It may not be superfluous to remind ourselves of this fact today, when sometimes righteously, but more often with no right whatsoever, scientific or social achievements are assaulted and when the behavior of certain unscrupulous people assumes a most aggressive character. The essence of the intrinsic virtue of the thing stipulates a much more positive and courageous mind, in social, public, religious and scientific domains, in order to defend all these accomplishments of mankind and save them for future generations.
In this sense I bid you a successful future resulting from your freshly acquired gemological knowledge; may many interesting tests be the source of personal satisfaction and happiness to you and the reason of increasing confidence placed in you by your clientele.
Dr Edward Gubelin's Address
In his address, following the presentation of awards to the Gemmological Association of Great Britain at Goldsmith’s Hall on 25th November, 1974, including candidates from many different parts of the world, Dr Edward Gubelin said:
What is happening on our planet today? I do not mean the belligerent tensions in the near East nor the failure to adopt a common energy policy nor the worldwide monetary crisis—no, what happens in this world as an entity, what happens at the present for the first time uniquely and so thoroughly that it will be remembered in the centuries to come, just a we still acknowledge and appreciate today the invention of the wheel, of the alphabet, the development of the great religions of the world, or from a geological point of view the folding up of the Alps, as an outstanding and irrevocable phenomenon. Well, what is happening in front of our eyes today? It is a tremendous and in its kind certainly a unique metamorphosis, which could at best compare with the change which mankind underwent during the dark ages and then again at the beginning of the Renaissance. The world happens to be in the midst of a fundamental change of structure with biological, physiological, sociological and even theological effects, and these are of such profundity that we cannot escape them.
To a certain extent we have been experiencing drastic changes also in our profession. Until recently, our idea of sales promotion moved along perspectives which had already been fixed in medieval times and which were almost exclusively limited to the mere action of selling, and best to a successful sales talk, while today after a short time of transition (calculating just a few years) great value is being placed in an extensive professional erudition, profound psychology, sound argumentation and efficient advice. While previously the old Roman warning Caveat Emptor, which originated from distrust, alerted the buyer to be careful, it now has the meaning that the client wishes to be well informed and accurately advised about the goods he is interested in purchasing. This desire may only be fulfilled by the salesman if he masters a fundamental professional knowledge. Science reigns today over all sequences of our life, medicine a well as commerce, production as well as communication, and the last consumer wishes to share in this professional science.
It is the aim of the gemological courses, which you have so successfully completed, to offer this specialized knowledge which will give you greater self-assurance and consequently increase well founded trust to assist your clients in such a way as to justify the confidence they place in your hands. The relatively broad spectrum of knowledge taught in the condensed form of, say, 25 or 30 assignments distributed over two courses challenged your capability to understand connexions and relationships which exist between different disciplines of the science of nature as well as between different properties of gemstones. The capacity of thinking in relationships and coordinations as well as the readiness to engage yourselves and to take responsibility and to accept solidarity should, apart from your technical achievement, be the human or spiritual benefit of your gemological study. In this sense, I wish to congratulate your most cordially on your successful attainment, which is the well deserved result of your perseverance and brave sacrifice during two years of intensive study. Not only your personal interest in gemology has led you to this award but also your thirst for knowledge and education, that marvelous, growing, aching process, whereby the mind develops into a usable instrument with a collection of proved experiences from which to function.
Some of you may consider the diploma examination as the climax of your gemological studies. Yet, may I bring to mind that this is rather the first ‘rung of the ladder’—that you have merely just crossed the threshold of a space spreading before you with no visible horizon, and the heady sensation you may feel now is only the beginning of further studies combined with unexpected experiences which perhaps are more closely linked with your practical everyday life in future. Therefore I recommend you to remain abreast of future developments by joining the advanced post diploma courses and subscribing to gemological periodicals.
Your diploma should not mislead you to consider yourselves as infallible experts. Your status quo is comparable to the situation of a young B.Sc or Ph.D who has just received his academic title, which does not attest him yet as a fully fledged scientist but merely that he has learnt to think and act independently and—as is to be hoped—with a sense of responsibility.
Among the resources offered to the modern science of nature gemology assumes a prominent place. Unfortunately it was considered a superfluous appendage and hardly acknowledged for almost a generation, and gemological publications only appeared as foot notes to mineralogical literature. Yet, indeed, as an independent basis, gemology has often supplied mineralogy with fundamental data and proved to be of invaluable assistance. Gemology was lacking professionalism for a long time and for far too long gemology was merely a trade accessory. Gemological degrees at present are still no more than school degrees, either rewarded by trade associations or by private institutes affiliated with the trade. An academic degree course would help in upgrading the profession’s standing similarly as university training would facilitate gemology and gemologists to meet the increasing technology and standard of investigation.
However, thanks to numerous outstanding achievements in highly scientific gemological research, today gemology is fully recognized as a science. As a matter of fact, gemology is today rightly entitled to claim the merit of having essentially contributed towards the astonishing progress of mineralogical research. The endeavor to expand as far as possible the boundaries within which may be possible, is a central motive of technical and scientific development. It is the same force which led our progenitors to master the use of fire and which drives us today to investigate outer space without knowing where this may lead us to. This intense desire of mankind to question all boundaries again and again is already grappled in the Genesis of the Old Testament by the words ‘Conquer the Earth with all that is within’ and thus deprived of any further argumentation. However, if man conquers the Earth, then he must corroborate by his mental disposition as well as by his moral conduct that he is indeed legitimized for this role—not only a scientist but also in his quality as a human being.
By this I mean to emphasize that we have a right to profit from our knowledge to our own personal advantage, yet never to use it to the harm of others. A French philosopher expressed this thought with the following word: ‘Science sans conscience n’est que ruine de l’ame’—science without conscience is the undoing of one’s soul. Scientific research means searching for the truth. Consequently, we are obliged to be honest and always tell the truth, and if we happen to make a mistake we should summon the courage to admit it.
Irrevocable laws do not only exist in the field of the sciences of nature but also in the sphere of human life and coexistence. In this connexion I may refer to the problematics of liberty and restraint, to all the tensions which occur because man is a personality who must develop in freedom, yet according to the laws of nature he is also a social being, who can only completely unfold himself in a society. It may not be superfluous to remind ourselves of this fact today, when sometimes righteously, but more often with no right whatsoever, scientific or social achievements are assaulted and when the behavior of certain unscrupulous people assumes a most aggressive character. The essence of the intrinsic virtue of the thing stipulates a much more positive and courageous mind, in social, public, religious and scientific domains, in order to defend all these accomplishments of mankind and save them for future generations.
In this sense I bid you a successful future resulting from your freshly acquired gemological knowledge; may many interesting tests be the source of personal satisfaction and happiness to you and the reason of increasing confidence placed in you by your clientele.
Azurite
Chemistry: Copper carbonate.
Crystal system: Monoclinic; short dense crystals; prismatic, often as spherical radiating groups or botryoidal masses.
Color: Semi-translucent to opaque; dark blue to violetish blue; some transparent crystals.
Hardness: 3.25 - 4
Cleavage: Perfect; Fracture: conchoidal to uneven, brittle.
Specific gravity: 3.7 – 3.9
Refractive index: 1.730 – 1.838; Biaxial positive; 0.108
Luster: Vitreous to waxy
Dichroism: Light blue/dark blue
Occurrence: Secondary ore of copper; found in oxidized portions of copper veins; France, S.Africa, USA, Australia, Russia.
Notes
Unstable. Usually found in conjunction with malachite ‘azurmalachite’; tough variety is called ‘royal gem azurite’ (Las Vagas, USA); effervesces with acid (hydrochloric acid).
Crystal system: Monoclinic; short dense crystals; prismatic, often as spherical radiating groups or botryoidal masses.
Color: Semi-translucent to opaque; dark blue to violetish blue; some transparent crystals.
Hardness: 3.25 - 4
Cleavage: Perfect; Fracture: conchoidal to uneven, brittle.
Specific gravity: 3.7 – 3.9
Refractive index: 1.730 – 1.838; Biaxial positive; 0.108
Luster: Vitreous to waxy
Dichroism: Light blue/dark blue
Occurrence: Secondary ore of copper; found in oxidized portions of copper veins; France, S.Africa, USA, Australia, Russia.
Notes
Unstable. Usually found in conjunction with malachite ‘azurmalachite’; tough variety is called ‘royal gem azurite’ (Las Vagas, USA); effervesces with acid (hydrochloric acid).
Gemmology On A Shoestring
(via The Journal of Gemmology, Vol.10, No.3, July 1966) B W Anderson writes:
It is a worthwhile exercise to make a list of all those gem materials which you believe you can confidently identify by lens inspection only—provided the specimens are clean, not too small, and that the lighting in good. The following list of ‘recognizable’ gems would probably be agreed to by most experienced gemologists, and could, I am sure, be extended: diamond, zircon, demantoid, peridot, opal, amethyst, star sapphire and ruby, chrysoberyl cat’s eye, quartz cat’s eye, iolite, tourmaline, hematite, marcasite, lapis lazuli, ‘Swiss’ lapis, aventurine quartz, bloodstone, ivory, pearl, pink pearl, cultured pearl, imitation pearl, paste, ‘goldstone’, doublets, synthetic star stones, synthetic rutile, strontium titanate, blue sinter spinel. Such a list of thirty materials at least makes an encouraging start; I shall suggest later the basis on which some of the above determinations may rest, and a few simple accessories which may make these and further identifications more simple and more sure.
That the stone examined should be clean (and here I am not referring to inner cleanliness) was stipulated just now, and it is certainly well worthwhile before examining a stone or stones to do a thorough job of cleaning. This is usually quite a simple matter in water containing a little liquid detergent, using soft toothbrush to get into any nooks and crannies of the setting if the stones are mounted. If the stones are then rinsed and shaken, and placed on blotting paper close below the bulb of a desk lamp, they will soon dry. Loose stones, if large, can be handled most safely in the fingers. With small stones, tongs are necessary: these should not be too sharp-nosed, and should have a mild spring. Those who have difficulty in maintaining the correct gentle pressure on the tongs to grip the stone safely while it is being examined may find tongs fitted with a ‘slide’ helpful, as these maintain a fixed pressure. An adjustable desk lamp with an opaque shade is a virtual necessity, enabling a strong light to shine on the specimen without dazzling the eye of the observer. In using a lens, a light interlocking of the left hand holding the specimen and the right hand holding the lens is essential to maintain steadiness and constant focus.
Let us now consider some of the main attributes which enable gemstones to be recognized for what they are.
Color
This is unquestionably the greatest aid of all, though of course it can sometimes be misleading. An attempt to sort out a parcel of mixed colorless stones will soon convince the skeptic how helpful color can be. The gemologist must also be on the look out for parti-coloration, as in many tourmalines; zoned or patchy color as in amethyst, ‘burnt amethyst’, sapphire; dichroism or change of color with direction as in ruby, tourmaline, andalusite, iolite, aquamarine.
Luster
This depends, of course upon the refractive index, but also upon the perfection of polish, which in turn depends largely upon hardness. The polished surface of a diamond will reflect 17% of a ray of light at perpendicular incidence, whereas quartz under the same conditions reflects only 4½% of light. Stones of intermediate refractive index, of course, reflect to extents between these two extremes, in accordance with Fresnel’s well-known formula. The luster of a diamond is certainly one of its outstanding characteristics, and luster can often play a part in distinguishing between similar gems, e.g. between chrysoberyl cat’s eye and quartz cat’s eye.
Fire
The gemologist will know that the effect known as ‘fire’ depends upon the ‘dispersion’ of a stone, which can be stated numerically as the difference between its refractive index for red light of chosen wavelength and for a chosen wavelength of violet light. Fire is most necessary in a colorless stone, if it is to have any beauty and liveliness. Diamond, of course, is our standard here, though considering its high index of refraction its dispersion is decidedly low. By comparison synthetic rutile and even strontium titanate seem to show a rather gaudy display of flashes of spectrum colors. Demantoid garnet owes its lively appearance both to its high luster and its fire: these features should serve to distinguish it at once from either emerald or peridot, even if its color did not. Although the dispersion of synthetic white spinel is only a little higher than that of white sapphire, it does show perceptibly more fire and this makes it a more plausible substitute for diamond, particularly in step cut form.
Transparency
This is contributory factor in the appearance of gemstones which is insufficiently appreciated. Most of the stones used in jewelry would be listed as ‘transparent’, and this would be true insofar as one could read print through a polished block of the stones concerned. But perfect transparency is possessed by very few minerals—diamond, synthetic spinel, and white topaz amongst them—while others, such as zircon, are almost always marred by a slight touch of milkiness. Perfect transparency is, of course, more important in colorless than in colored stones.
Double Refraction
The detection of double refraction in transparent gemstones, and the approximate assessment of its strength, are matters of prime importance in the lens identification of a given specimen, and it is here that a gemologist should score heavily over his unscientific colleagues. The ‘doubling of the back facets’ when viewed through the front of a stone with a lens is very easily in zircon (double refraction 0.06) and sphene (0.13), also in peridot (0.036) and even tourmaline (0.02): but one may need considerable skill in detecting it in quartz and in topaz (0.01, approx.) unless the stone be a large one. It is very important to remember that in all doubly refracting stones there are either one or two ‘optic axes’ along which no double refraction can be observed, and that at right angles to these directions the doubling cannot be seen either, since one image is directly behind the other. Thus one must turn and twist the stone, peering through it at the further facet junctions in all possible directions before deciding whether or not D.R is present, and if so, approximately how strong. Naturally, the larger the stone the greater the effect, and this must be taken into consideration in any assessment made.
Gemmology On A Shoestring (continued)
It is a worthwhile exercise to make a list of all those gem materials which you believe you can confidently identify by lens inspection only—provided the specimens are clean, not too small, and that the lighting in good. The following list of ‘recognizable’ gems would probably be agreed to by most experienced gemologists, and could, I am sure, be extended: diamond, zircon, demantoid, peridot, opal, amethyst, star sapphire and ruby, chrysoberyl cat’s eye, quartz cat’s eye, iolite, tourmaline, hematite, marcasite, lapis lazuli, ‘Swiss’ lapis, aventurine quartz, bloodstone, ivory, pearl, pink pearl, cultured pearl, imitation pearl, paste, ‘goldstone’, doublets, synthetic star stones, synthetic rutile, strontium titanate, blue sinter spinel. Such a list of thirty materials at least makes an encouraging start; I shall suggest later the basis on which some of the above determinations may rest, and a few simple accessories which may make these and further identifications more simple and more sure.
That the stone examined should be clean (and here I am not referring to inner cleanliness) was stipulated just now, and it is certainly well worthwhile before examining a stone or stones to do a thorough job of cleaning. This is usually quite a simple matter in water containing a little liquid detergent, using soft toothbrush to get into any nooks and crannies of the setting if the stones are mounted. If the stones are then rinsed and shaken, and placed on blotting paper close below the bulb of a desk lamp, they will soon dry. Loose stones, if large, can be handled most safely in the fingers. With small stones, tongs are necessary: these should not be too sharp-nosed, and should have a mild spring. Those who have difficulty in maintaining the correct gentle pressure on the tongs to grip the stone safely while it is being examined may find tongs fitted with a ‘slide’ helpful, as these maintain a fixed pressure. An adjustable desk lamp with an opaque shade is a virtual necessity, enabling a strong light to shine on the specimen without dazzling the eye of the observer. In using a lens, a light interlocking of the left hand holding the specimen and the right hand holding the lens is essential to maintain steadiness and constant focus.
Let us now consider some of the main attributes which enable gemstones to be recognized for what they are.
Color
This is unquestionably the greatest aid of all, though of course it can sometimes be misleading. An attempt to sort out a parcel of mixed colorless stones will soon convince the skeptic how helpful color can be. The gemologist must also be on the look out for parti-coloration, as in many tourmalines; zoned or patchy color as in amethyst, ‘burnt amethyst’, sapphire; dichroism or change of color with direction as in ruby, tourmaline, andalusite, iolite, aquamarine.
Luster
This depends, of course upon the refractive index, but also upon the perfection of polish, which in turn depends largely upon hardness. The polished surface of a diamond will reflect 17% of a ray of light at perpendicular incidence, whereas quartz under the same conditions reflects only 4½% of light. Stones of intermediate refractive index, of course, reflect to extents between these two extremes, in accordance with Fresnel’s well-known formula. The luster of a diamond is certainly one of its outstanding characteristics, and luster can often play a part in distinguishing between similar gems, e.g. between chrysoberyl cat’s eye and quartz cat’s eye.
Fire
The gemologist will know that the effect known as ‘fire’ depends upon the ‘dispersion’ of a stone, which can be stated numerically as the difference between its refractive index for red light of chosen wavelength and for a chosen wavelength of violet light. Fire is most necessary in a colorless stone, if it is to have any beauty and liveliness. Diamond, of course, is our standard here, though considering its high index of refraction its dispersion is decidedly low. By comparison synthetic rutile and even strontium titanate seem to show a rather gaudy display of flashes of spectrum colors. Demantoid garnet owes its lively appearance both to its high luster and its fire: these features should serve to distinguish it at once from either emerald or peridot, even if its color did not. Although the dispersion of synthetic white spinel is only a little higher than that of white sapphire, it does show perceptibly more fire and this makes it a more plausible substitute for diamond, particularly in step cut form.
Transparency
This is contributory factor in the appearance of gemstones which is insufficiently appreciated. Most of the stones used in jewelry would be listed as ‘transparent’, and this would be true insofar as one could read print through a polished block of the stones concerned. But perfect transparency is possessed by very few minerals—diamond, synthetic spinel, and white topaz amongst them—while others, such as zircon, are almost always marred by a slight touch of milkiness. Perfect transparency is, of course, more important in colorless than in colored stones.
Double Refraction
The detection of double refraction in transparent gemstones, and the approximate assessment of its strength, are matters of prime importance in the lens identification of a given specimen, and it is here that a gemologist should score heavily over his unscientific colleagues. The ‘doubling of the back facets’ when viewed through the front of a stone with a lens is very easily in zircon (double refraction 0.06) and sphene (0.13), also in peridot (0.036) and even tourmaline (0.02): but one may need considerable skill in detecting it in quartz and in topaz (0.01, approx.) unless the stone be a large one. It is very important to remember that in all doubly refracting stones there are either one or two ‘optic axes’ along which no double refraction can be observed, and that at right angles to these directions the doubling cannot be seen either, since one image is directly behind the other. Thus one must turn and twist the stone, peering through it at the further facet junctions in all possible directions before deciding whether or not D.R is present, and if so, approximately how strong. Naturally, the larger the stone the greater the effect, and this must be taken into consideration in any assessment made.
Gemmology On A Shoestring (continued)
Friday, July 06, 2007
Clear And Present
An interesting article on lighting(for colored stone dealers + diamond dealers + jewelers + consumers). Only a few know the differences between sunlight, daylight and skylight and its effect on human when viewing a colored object, in this case, gemstones, diamonds and jewelry.
Himanshu Burte writes:
Daylight is the most comfortable kind of light for the eyes, reduces fatigue on the job, keeps us connected to the cylce of day and season, and sustains our morale.
Daylight is among the best things in life that come free. And when correctly integrated with adjustable artificial lighting, it can actually be an important factor, particularly in the stressful modern workplace. Its links with general well-being are well documented: It is the most comfortable kind of light for the eyes, reduces fatigue on the job, keeps us connected to the cycle of the day and season, and sustains our morale. And yet, rare is the office in which the “skydome” is the predominant source of light. Why?
Some reasons have to do with the difficulties of harnessing daylight itself. Others are rooted in broader factors such as city planning, cost of real estate and building plans. The difficulty is that light always comes with heat and glare, whether it is from the sun or a lighting system. Thus, improperly managed direct sunlight in a glazed building, say, can make air conditioning very costly. Properly managed, however, daylight generates less heat for the same amount and better quality of light than most electrical lighting systems, and can actually reduce the air-conditioning load. Architectural and interior design are also implicated. For instance, where an office has closed cabins hogging the limited windows length, daylighting for the open office core is quickly sacrificed. Since few decision makers know about the positive relationship between daylight and productivity, the sacrifice is easily made.
Good daylighting design begins with simple principles. In India, almost always, light from the north sky is relatively glare-free and consistent across the day. Of course, other daylighting strategies have to be region-specific. In hot, dry parts, such as in North India, it is best to bring the sun in indirectly and sideways. Here, small openings to the exterior, especially to the west and east from where the sun enters at a low angle and penetrates deep, are appropriate. Bounce sunlight off vertical or horizontal baffles or light wells—such as tiny courtyards of desert houses—before it enters indoors, so that it has already lost some heat and glare. In the humid coastal areas where temperatures don’t reach New Delhi’s levels, however, windows may have to be larger to let in breeze to blow away sweat from the skin. Here, in fact, it may be useful to have one set of openings for breeze and local light and another higher up for general lighting. This only illustrates the most important fact: If it is to work, daylight must be integrated intelligently with many other systems that make up a building.
More info @ http://www.livemint.com/2007/07/05002443/Clear-and-present.html
Himanshu Burte writes:
Daylight is the most comfortable kind of light for the eyes, reduces fatigue on the job, keeps us connected to the cylce of day and season, and sustains our morale.
Daylight is among the best things in life that come free. And when correctly integrated with adjustable artificial lighting, it can actually be an important factor, particularly in the stressful modern workplace. Its links with general well-being are well documented: It is the most comfortable kind of light for the eyes, reduces fatigue on the job, keeps us connected to the cycle of the day and season, and sustains our morale. And yet, rare is the office in which the “skydome” is the predominant source of light. Why?
Some reasons have to do with the difficulties of harnessing daylight itself. Others are rooted in broader factors such as city planning, cost of real estate and building plans. The difficulty is that light always comes with heat and glare, whether it is from the sun or a lighting system. Thus, improperly managed direct sunlight in a glazed building, say, can make air conditioning very costly. Properly managed, however, daylight generates less heat for the same amount and better quality of light than most electrical lighting systems, and can actually reduce the air-conditioning load. Architectural and interior design are also implicated. For instance, where an office has closed cabins hogging the limited windows length, daylighting for the open office core is quickly sacrificed. Since few decision makers know about the positive relationship between daylight and productivity, the sacrifice is easily made.
Good daylighting design begins with simple principles. In India, almost always, light from the north sky is relatively glare-free and consistent across the day. Of course, other daylighting strategies have to be region-specific. In hot, dry parts, such as in North India, it is best to bring the sun in indirectly and sideways. Here, small openings to the exterior, especially to the west and east from where the sun enters at a low angle and penetrates deep, are appropriate. Bounce sunlight off vertical or horizontal baffles or light wells—such as tiny courtyards of desert houses—before it enters indoors, so that it has already lost some heat and glare. In the humid coastal areas where temperatures don’t reach New Delhi’s levels, however, windows may have to be larger to let in breeze to blow away sweat from the skin. Here, in fact, it may be useful to have one set of openings for breeze and local light and another higher up for general lighting. This only illustrates the most important fact: If it is to work, daylight must be integrated intelligently with many other systems that make up a building.
More info @ http://www.livemint.com/2007/07/05002443/Clear-and-present.html
Conflict Diamonds: A New Dataset
Elisabeth Gilmore, Nils Petter Gleditsch, Päivi Lujala & Jan Ketil Rød writes:
Natural resources, and diamonds especially, are commonly believed to play a significant role in the onset and duration of armed civil conflict. Although there is ample case study evidence that diamonds and similar resources have been used by rebel groups to finance fighting, there are few systematic empirical studies assessing the role of lootable resources in civil conflict. This is largely due to lack of reliable data on production and location.
In this article we discuss priorities for the collection of data on conflict-relevant resources and introduce a new dataset, DIADATA that provides a comprehensive list of diamond deposits accompanied by geographic coordinates throughout the world. The dataset includes characteristics relevant to conflict such as production status and geological form of the deposit. Particularly important is the distinction between primary and secondary diamonds, because the latter are more easily lootable. The dataset incorporates a spatial as well as a temporal dimension.
More info @ http://www.prio.no/page/Publication_details/9429/47113.html
http://www.prio.no/page/9649/47115.html
Natural resources, and diamonds especially, are commonly believed to play a significant role in the onset and duration of armed civil conflict. Although there is ample case study evidence that diamonds and similar resources have been used by rebel groups to finance fighting, there are few systematic empirical studies assessing the role of lootable resources in civil conflict. This is largely due to lack of reliable data on production and location.
In this article we discuss priorities for the collection of data on conflict-relevant resources and introduce a new dataset, DIADATA that provides a comprehensive list of diamond deposits accompanied by geographic coordinates throughout the world. The dataset includes characteristics relevant to conflict such as production status and geological form of the deposit. Particularly important is the distinction between primary and secondary diamonds, because the latter are more easily lootable. The dataset incorporates a spatial as well as a temporal dimension.
More info @ http://www.prio.no/page/Publication_details/9429/47113.html
http://www.prio.no/page/9649/47115.html
Cave Home Auctioned For £100,000
A very interesting story.
BBC News writes:
A cave home in Worcestershire complete with a front door, fireplace and pantry, has been sold for £100,000. Rock Cottage in Wolverley, which is hewn out of a sandstone cliff and has three adjoining caves, was last occupied in the late 1940s.
It was auctioned by Halls estate agency for four times its £25,000 guide price. The cave, which comes with windows, a sitting room and bedroom but has no electricity or water supply, generated more than 50 requests for viewings.
'Unbelievable interest'.
A near-neighbour bought the Sladd Lane property because she wanted it "to stay exactly how it is", auctioneer Roger Sadler said.
He added that people came from as far away as Spain to the auction on Wednesday. Mr Sadler said: "We are very pleased. You don't sell caves very often but it was a unique property that attracted an unbelievable amount of interest."
The cave, sold with five acres of mixed woodland and associated garden land, was auctioned off following the death of the current owner. Experts say it is questionable whether it would be suitable for human habitation.
More info @ http://news.bbc.co.uk/2/hi/uk_news/england/hereford/worcs/6271564.stm
BBC News writes:
A cave home in Worcestershire complete with a front door, fireplace and pantry, has been sold for £100,000. Rock Cottage in Wolverley, which is hewn out of a sandstone cliff and has three adjoining caves, was last occupied in the late 1940s.
It was auctioned by Halls estate agency for four times its £25,000 guide price. The cave, which comes with windows, a sitting room and bedroom but has no electricity or water supply, generated more than 50 requests for viewings.
'Unbelievable interest'.
A near-neighbour bought the Sladd Lane property because she wanted it "to stay exactly how it is", auctioneer Roger Sadler said.
He added that people came from as far away as Spain to the auction on Wednesday. Mr Sadler said: "We are very pleased. You don't sell caves very often but it was a unique property that attracted an unbelievable amount of interest."
The cave, sold with five acres of mixed woodland and associated garden land, was auctioned off following the death of the current owner. Experts say it is questionable whether it would be suitable for human habitation.
More info @ http://news.bbc.co.uk/2/hi/uk_news/england/hereford/worcs/6271564.stm
Gemmology On A Shoestring
2007: B W Anderson is one of the god fathers of gemology. His inspiring note (s) on how to identify stones with simple instruments + warning the gemologist (s) against an over dependence upon instruments + the need to use the power of observation (s) to the full + interpret what is seen in simple terms, is a friendly reminder to any enterprising gem dealer/jeweler.
Today we have new diamond simulants like synthetic cubic zirconia, synthetic moissanite and others + new synthetic corundums + new synthetic diamonds + new synthetic beryls + new, modified colored stone treatments to keep gem dealers/jewelers/gemologists/ lab gemologists busy/awake for the rest of their lives.
(via The Journal of Gemmology, Vol.10, No.3, July 1966) B W Anderson writes:
On several occasions I have given talks to post-diploma students under the title ‘Gem testing without instruments’, which I believe have been helpful in warning the student, fresh from his examinations, against an over-dependence upon instruments in his endeavors to identify gemstones. ‘Gemmology on a Shoestring’ is intended to follow much the same theme, but the title purposely suggests a little latitude in allowing for the use of quite simple pieces of apparatus, liquids, and so on, which can aid considerably in making firm decisions instead of merely forming opinions in certain cases.
First I must make it quite clear that to solve many of the problems that confront the gemologist in these days every available instrument may be valuable and necessary if a correct answer is to be ensured. My present intention is not so much to provide easy recipes for individual cases of identification as to persuade those who have gemological training to use their powers of observation to the full and interpret what is seen in the light of their special knowledge. It has often been said that the limited amount of scientific knowledge absorbed in the two year course can actually be a handicap to a young jeweler: into every yellow zircon he dreams a sphene, and in viewing a parcel of tourmalines his mind is cluttered with thoughts of kornerupine. There is enough truth in this to sting a little; but I strongly maintain that in a ‘lens only’ identification test on mixed series of gemstones, the man with a gemological training should be far more sure of his ground than a colleague of otherwise equal ability and experience. As any good artist knows, it is a fallacy to think that any two people of normal eyesight gazing at a given object are necessarily seeing the same thing. It is the interpretation of the image falling on the retina that may enable the artist to see a significant and exciting pattern of shapes, shadows and colors, where his friend may see nothing of any interest whatsoever. In like manner a jeweler who is not a gemologist, when confronted by a mounted and well-cut white zircon, may well feel that it ‘doesn’t look quite right’ for a diamond, but his gemologist friend, noting the strong double refraction in the stone, will be able to make a quite positive identification.
Sheer economic necessity may deprive the average young gemologist of the three really essential instruments for gem identification—the microscope, refractometer, and spectroscope. Ten years or so ago less than fifty pounds would have been required to but the lot: today one may have to pay at least twice as much as this. Indeed the simple liquids which will be recommended in this talk are now so costly that one must ruefully admit that even ‘shoestrings’ have become expensive. Against this one must realize that in the precious stone trade a mistake mean a loss of hundred of pounds or a damaged reputation, and the cost of any instrument which can save such mistakes, or a fee for a laboratory test, is money wisely spent.
To start with, I shall assume that the jeweler has only one ‘instrument’—a pocket lens, and proceed to consider what he can learn about gems with this as his only aid. A good lens is so vitally important that I do insist—make it a good one, magnifying eight or ten diameters. Lower powers are of comparatively little use, however suitable for the scrutiny of watches or hallmarks—while higher powers are difficult to handle and not nearly so flexible in their application.
In our first assessment of any gemstone we are all inevitably influenced in our thinking by its general appearance, which, when analyzed, depends chiefly upon its color, luster, degree of transparency, and ‘fire’. If the stone is unmounted, we may notice from our first ‘feel’ of it is cold or relatively warm to the touch, that it gives a slippery or harsh impression when handled, or that it strikes one as ‘heavy’ or ‘light’ in the hand. Then may follow close examination with a lens. The back facet edges may appear doubled, there may be characteristic inclusion, cleavage chips may appear on the girdle, and so on. All these phenomena may either be accurately measurable or more closely investigated with instruments: our task is to learn all that we can without them—even if later some form of instrument may have to be used as a final court of appeal.
Gemmology On A Shoestring (continued)
Today we have new diamond simulants like synthetic cubic zirconia, synthetic moissanite and others + new synthetic corundums + new synthetic diamonds + new synthetic beryls + new, modified colored stone treatments to keep gem dealers/jewelers/gemologists/ lab gemologists busy/awake for the rest of their lives.
(via The Journal of Gemmology, Vol.10, No.3, July 1966) B W Anderson writes:
On several occasions I have given talks to post-diploma students under the title ‘Gem testing without instruments’, which I believe have been helpful in warning the student, fresh from his examinations, against an over-dependence upon instruments in his endeavors to identify gemstones. ‘Gemmology on a Shoestring’ is intended to follow much the same theme, but the title purposely suggests a little latitude in allowing for the use of quite simple pieces of apparatus, liquids, and so on, which can aid considerably in making firm decisions instead of merely forming opinions in certain cases.
First I must make it quite clear that to solve many of the problems that confront the gemologist in these days every available instrument may be valuable and necessary if a correct answer is to be ensured. My present intention is not so much to provide easy recipes for individual cases of identification as to persuade those who have gemological training to use their powers of observation to the full and interpret what is seen in the light of their special knowledge. It has often been said that the limited amount of scientific knowledge absorbed in the two year course can actually be a handicap to a young jeweler: into every yellow zircon he dreams a sphene, and in viewing a parcel of tourmalines his mind is cluttered with thoughts of kornerupine. There is enough truth in this to sting a little; but I strongly maintain that in a ‘lens only’ identification test on mixed series of gemstones, the man with a gemological training should be far more sure of his ground than a colleague of otherwise equal ability and experience. As any good artist knows, it is a fallacy to think that any two people of normal eyesight gazing at a given object are necessarily seeing the same thing. It is the interpretation of the image falling on the retina that may enable the artist to see a significant and exciting pattern of shapes, shadows and colors, where his friend may see nothing of any interest whatsoever. In like manner a jeweler who is not a gemologist, when confronted by a mounted and well-cut white zircon, may well feel that it ‘doesn’t look quite right’ for a diamond, but his gemologist friend, noting the strong double refraction in the stone, will be able to make a quite positive identification.
Sheer economic necessity may deprive the average young gemologist of the three really essential instruments for gem identification—the microscope, refractometer, and spectroscope. Ten years or so ago less than fifty pounds would have been required to but the lot: today one may have to pay at least twice as much as this. Indeed the simple liquids which will be recommended in this talk are now so costly that one must ruefully admit that even ‘shoestrings’ have become expensive. Against this one must realize that in the precious stone trade a mistake mean a loss of hundred of pounds or a damaged reputation, and the cost of any instrument which can save such mistakes, or a fee for a laboratory test, is money wisely spent.
To start with, I shall assume that the jeweler has only one ‘instrument’—a pocket lens, and proceed to consider what he can learn about gems with this as his only aid. A good lens is so vitally important that I do insist—make it a good one, magnifying eight or ten diameters. Lower powers are of comparatively little use, however suitable for the scrutiny of watches or hallmarks—while higher powers are difficult to handle and not nearly so flexible in their application.
In our first assessment of any gemstone we are all inevitably influenced in our thinking by its general appearance, which, when analyzed, depends chiefly upon its color, luster, degree of transparency, and ‘fire’. If the stone is unmounted, we may notice from our first ‘feel’ of it is cold or relatively warm to the touch, that it gives a slippery or harsh impression when handled, or that it strikes one as ‘heavy’ or ‘light’ in the hand. Then may follow close examination with a lens. The back facet edges may appear doubled, there may be characteristic inclusion, cleavage chips may appear on the girdle, and so on. All these phenomena may either be accurately measurable or more closely investigated with instruments: our task is to learn all that we can without them—even if later some form of instrument may have to be used as a final court of appeal.
Gemmology On A Shoestring (continued)
Axinite
Chemistry: Complex calcium aluminum borosilicate
Crystal system: Triclinic; bladed, wedge-shaped crystals; lamellar masses
Color: Transparent to translucent; brown, more rarely yellow, violet, blue.
Hardness: 6.5 - 7
Cleavage: Perfect: in one direction; Fracture: brittle, conchoidal to uneven.
Specific gravity: 3.28 (3.27 – 3.29)
Refractive index: 1.675 – 1.685; Biaxial negative; 0.010 – 0.012
Luster: Greasy to vitreous
Dichroism: Strong; olive to strong green/violet blue; brown/yellow.
Occurrence: In areas of contact metamorphism; France, Mexico, USA, Sri Lanka, Pakistan.
Notes
Axinite is named after axe-like shape of crystals. The specimens may look like smoky quartz; piezo electric; no luminescence in gem quality specimens but may show in yellow as reddish glow; some show phosphorescence; spectrum: yellow—3 bands, 1 narrow in blue/green, 2 broaded in blue 512, 492, 466nm; faceted for collectors.
Crystal system: Triclinic; bladed, wedge-shaped crystals; lamellar masses
Color: Transparent to translucent; brown, more rarely yellow, violet, blue.
Hardness: 6.5 - 7
Cleavage: Perfect: in one direction; Fracture: brittle, conchoidal to uneven.
Specific gravity: 3.28 (3.27 – 3.29)
Refractive index: 1.675 – 1.685; Biaxial negative; 0.010 – 0.012
Luster: Greasy to vitreous
Dichroism: Strong; olive to strong green/violet blue; brown/yellow.
Occurrence: In areas of contact metamorphism; France, Mexico, USA, Sri Lanka, Pakistan.
Notes
Axinite is named after axe-like shape of crystals. The specimens may look like smoky quartz; piezo electric; no luminescence in gem quality specimens but may show in yellow as reddish glow; some show phosphorescence; spectrum: yellow—3 bands, 1 narrow in blue/green, 2 broaded in blue 512, 492, 466nm; faceted for collectors.
Thursday, July 05, 2007
What's New, Pussycat
Memorable quote (s) from the movie:
Dr. Fritz Fassbender (Peter Sellers): I am a doctor of the mind.
Victor Skakapopulis (Woody Allen): Really?
Dr. Fritz Fassbender (Peter Sellers): Yes!
Victor Skakapopulis (Woody Allen): I have terrible emotional problems. Could you help me?
Dr. Fritz Fassbender (Peter Sellers): You certainly picked a very odd time to ask me, just in the middle of a suicide.
Dr. Fritz Fassbender (Peter Sellers): I am a doctor of the mind.
Victor Skakapopulis (Woody Allen): Really?
Dr. Fritz Fassbender (Peter Sellers): Yes!
Victor Skakapopulis (Woody Allen): I have terrible emotional problems. Could you help me?
Dr. Fritz Fassbender (Peter Sellers): You certainly picked a very odd time to ask me, just in the middle of a suicide.
The Science Of Success
James Surowiecki writes about MediaPredict + the prediction market + the concept of tapping the collective intelligence of everyone playing the market + other viewpoints @ http://www.newyorker.com/talk/financial/2007/07/09/070709ta_talk_surowiecki
Subscribe to:
Posts (Atom)