Wednesday, July 25, 2007
The Luxury Of Dreams
Chaim Even-Zohar writes about the World Diamond Congress + the impacts of the diamond dream + diamond demand, supply and market structure + other viewpoints @ http://www.idexonline.com/portal_FullEditorial.asp?TextSearch=&KeyMatch=0&id=25842
Cosmetics And Gem Materials
(via The Journal of Gemmology, Vol. IX, No.8, October 1964) R Webster writes:
Chalcedony
The only case of possible attack by cosmetics on chalcedony was one referred to the writer some time ago, and for which, at the time, no decision was reached, particularly as the change seemed so fantastic. Here a lady’s signet ring, set (presumably) with a black onyx, was submitted for investigation. The story which came with the enquiry was that the black stone was originally red (cornelian or stained agate) and had turned black. The owner of the ring was said to be a hairdresser and it was questioned whether chemicals used for hair-treatment could have caused the change of color. No information was given as to the nature of the chemicals used, or the type of hair-dressing preparations used by this hair-dresser. The only question asked was whether such an occurrence had been encountered before. To the best of my knowledge it had not, or at least had not been reported, and the matter rested there.
However, intrigued by the effect which, presumably, had occurred with the stone in the lady’s ring, some experiments were carried out. A piece of cornelian, probably dyed agate, was immersed in a tube of 25% sodium sulphide and left for some time, after which it was removed and dried. No apparent effect was then noticed, but some time later, after the stone had lain on a shelf open to daylight, the stone was seen to have darkened, but admittedly did not turn black but to a very dark brown. The notion underlying this experiment was that as the color of cornelian was due to iron, the action of the sodium sulphide might produce the black ferrous sulphide (FeS).
To perform the second experiment a small piece was broken off from the blackened specimen and immersed in a 20-volume solution of hydrogen peroxide and left for twenty four hours. On the removal of the piece from the solution it was seen that it had returned to the original reddish color, that of cornelian. Another piece was broken off the darkened specimen and immersed in ordinary tap water in order to check whether the darkening was just surface deposit which could be washed off. No lightening took place even after three days immersion. Whether the hydrogen peroxide solution would return the color when other dyes were used is a matter for debate and further experiment.
To get further information the writer approached the technical staff of Golden Ltd, the makers and distributors of the hairdressing products of L’Oreal of Paris, who were good enough to submit specimens of cornelian to treatments with some of their products. These tests involved immersion in samples of Pastel and Progress cold-wave lotions, Ciloreal-skin-stain remover, and a number of basic chemicals used in the manufacturing of L’Oreal products, both for hair coloring and permanent waving. Tests were also carried out by the Golden technicians with a 10% sodium sulphide solution; and one stringent test was with a Pastel cold wave No.1 at a temperature of 75ºC for eight hours. On the return of the stones, in no single instance was any blackening of the stones noticed. Later, however, after the stones had been kept in a stone paper for a few months, two of the pieces did seem to have somewhat darkened in color, but they certainly had not turned black.
It is clear from the above that any change in the color of cornelian could only occur after prolonged treatment, as in the case of the hairdresser who could well be using cosmetic chemicals daily, and would anyway be of rare occurrence, and not an expensive item to replace, but it does illustrate what troubles can be encountered.
The objects of this article is to warn the jeweler that cosmetics, when incorrectly used, may have a deleterious effect on certain types of gem materials. This is no criticism of beauty preparations in themselves when they are used with common sense, but so often ladies are oblivious to the fact that they are wearing their jewelry when completing the final touches to their make-up; then the jeweler is challenged as to the resultant changes.
Chalcedony
The only case of possible attack by cosmetics on chalcedony was one referred to the writer some time ago, and for which, at the time, no decision was reached, particularly as the change seemed so fantastic. Here a lady’s signet ring, set (presumably) with a black onyx, was submitted for investigation. The story which came with the enquiry was that the black stone was originally red (cornelian or stained agate) and had turned black. The owner of the ring was said to be a hairdresser and it was questioned whether chemicals used for hair-treatment could have caused the change of color. No information was given as to the nature of the chemicals used, or the type of hair-dressing preparations used by this hair-dresser. The only question asked was whether such an occurrence had been encountered before. To the best of my knowledge it had not, or at least had not been reported, and the matter rested there.
However, intrigued by the effect which, presumably, had occurred with the stone in the lady’s ring, some experiments were carried out. A piece of cornelian, probably dyed agate, was immersed in a tube of 25% sodium sulphide and left for some time, after which it was removed and dried. No apparent effect was then noticed, but some time later, after the stone had lain on a shelf open to daylight, the stone was seen to have darkened, but admittedly did not turn black but to a very dark brown. The notion underlying this experiment was that as the color of cornelian was due to iron, the action of the sodium sulphide might produce the black ferrous sulphide (FeS).
To perform the second experiment a small piece was broken off from the blackened specimen and immersed in a 20-volume solution of hydrogen peroxide and left for twenty four hours. On the removal of the piece from the solution it was seen that it had returned to the original reddish color, that of cornelian. Another piece was broken off the darkened specimen and immersed in ordinary tap water in order to check whether the darkening was just surface deposit which could be washed off. No lightening took place even after three days immersion. Whether the hydrogen peroxide solution would return the color when other dyes were used is a matter for debate and further experiment.
To get further information the writer approached the technical staff of Golden Ltd, the makers and distributors of the hairdressing products of L’Oreal of Paris, who were good enough to submit specimens of cornelian to treatments with some of their products. These tests involved immersion in samples of Pastel and Progress cold-wave lotions, Ciloreal-skin-stain remover, and a number of basic chemicals used in the manufacturing of L’Oreal products, both for hair coloring and permanent waving. Tests were also carried out by the Golden technicians with a 10% sodium sulphide solution; and one stringent test was with a Pastel cold wave No.1 at a temperature of 75ºC for eight hours. On the return of the stones, in no single instance was any blackening of the stones noticed. Later, however, after the stones had been kept in a stone paper for a few months, two of the pieces did seem to have somewhat darkened in color, but they certainly had not turned black.
It is clear from the above that any change in the color of cornelian could only occur after prolonged treatment, as in the case of the hairdresser who could well be using cosmetic chemicals daily, and would anyway be of rare occurrence, and not an expensive item to replace, but it does illustrate what troubles can be encountered.
The objects of this article is to warn the jeweler that cosmetics, when incorrectly used, may have a deleterious effect on certain types of gem materials. This is no criticism of beauty preparations in themselves when they are used with common sense, but so often ladies are oblivious to the fact that they are wearing their jewelry when completing the final touches to their make-up; then the jeweler is challenged as to the resultant changes.
Idocrase (Vesuvianite)
Chemistry: Calcium aluminum silicate.
Crystal system: Tetragonal; Vesuvianite: well-developed square prisms capped with bipyramidal and often basal pinacoid; Californite: massive; Cyprine: massive.
Color: Vesuvianite: transparent, yellow to brown and greenish shades; Californite: transparent to opaque; massive green (mixture of idocrase and grossular garnet); Cyprine: very rare blue variety (Cu).
Hardness: 6 - 7
Cleavage: Indistinct; Fracture: sub-conchoidal.
Specific gravity: 3.35
Refractive index: 1.70 – 1.73 (changes from negative to positive with increasing R.I); 0.005
Luster: Vitreous.
Dispersion: Low
Dichroism: Indistinct.
Occurrence: Canada, Italy, Switzerland, Siberia; Californite: California, USA.
Notes
Vesuvianite cut for collectors; crystals similar to zircon, except zircon rarely shows the basal pinacoid; massive green Californite may look like nephrite jade; massive idocrase often mixed with hydrogrossular; may show rare earth spectrum, strong band at 461nm in the blue; transparent varieties faceted; Californite: cabochon and beads.
Crystal system: Tetragonal; Vesuvianite: well-developed square prisms capped with bipyramidal and often basal pinacoid; Californite: massive; Cyprine: massive.
Color: Vesuvianite: transparent, yellow to brown and greenish shades; Californite: transparent to opaque; massive green (mixture of idocrase and grossular garnet); Cyprine: very rare blue variety (Cu).
Hardness: 6 - 7
Cleavage: Indistinct; Fracture: sub-conchoidal.
Specific gravity: 3.35
Refractive index: 1.70 – 1.73 (changes from negative to positive with increasing R.I); 0.005
Luster: Vitreous.
Dispersion: Low
Dichroism: Indistinct.
Occurrence: Canada, Italy, Switzerland, Siberia; Californite: California, USA.
Notes
Vesuvianite cut for collectors; crystals similar to zircon, except zircon rarely shows the basal pinacoid; massive green Californite may look like nephrite jade; massive idocrase often mixed with hydrogrossular; may show rare earth spectrum, strong band at 461nm in the blue; transparent varieties faceted; Californite: cabochon and beads.
Cirque du Soleil
New Business Model: An excellent insight + a new definition for competition.
(via emergic) An excerpt from the book, Blue Ocean Strategy, in Fast Company:
A one time accordion player, stilt-walker and fire-eater, Guy Laliberte is now CEO of one of Canada's largest cultural exports, Cirque du Soleil (http://www.cirquedusoleil.com). Created in 1984 by a group of street performers, Cirque's productions have been seen by almost 40 million people in 90 cities around the world. In less than 20 years Cirque du Soleil has achieved a revenue level that took Ringling Brothers and Barnum & Bailey's Circus - the global champion of the circus industry - more than one hundred years to attain.
What makes this all the more remarkable is that this rapid growth was not achieved in an attractive industry. It was in a declining industry in which traditional strategic analysis pointed to limited potential for growth. Supplier power on the part of star performers was strong. So was buyer power? From the perspective of competition-based strategy, then, the circus industry appeared unattractive.
Another compelling aspect of Cirque du Soleil's success is that it did not win by taking customers from the already shrinking demand for the circus industry, which historically catered to children. Cirque du Soleil did not compete with Ringling Brothers and Barnum & Bailey's Circus to make this happen. Instead it created uncontested new market space that made the competition irrelevant. It appealed to a whole new group of customers - adults and corporate clients prepared to pay a price that is several times as expensive as traditional circuses for their unprecedented entertainment experience. Significantly, one of the first Cirque productions was titled "We Reinvent the Circus".
Cirque du Soleil succeeded because it realized that to win in the future, companies must stop competing with each other. The only way to beat the competition is to stop trying to beat the competition.
In a brief article in Fast Company, Renee Mauborgne, the co-author of Blue Ocean Strategy, says companies can do what Cirque du Soleil did by following certain guidelines.
- Water, water, everywhere.
- You don't have to compete in a red ocean of bloody competition. Even exhausted industries -- like the circus can be reinvented.
- Don't swim with the school.
- Quit benchmarking the competition or setting your strategic agenda in the context of theirs.
- Find new ponds to fish.
- Don't assume your current customers have the insights you need to rethink your strategy. Look to non-customers instead.
- Cut bait on costs.
- Put as much emphasis on what you can eliminate as on what you can create.
(via emergic) An excerpt from the book, Blue Ocean Strategy, in Fast Company:
A one time accordion player, stilt-walker and fire-eater, Guy Laliberte is now CEO of one of Canada's largest cultural exports, Cirque du Soleil (http://www.cirquedusoleil.com). Created in 1984 by a group of street performers, Cirque's productions have been seen by almost 40 million people in 90 cities around the world. In less than 20 years Cirque du Soleil has achieved a revenue level that took Ringling Brothers and Barnum & Bailey's Circus - the global champion of the circus industry - more than one hundred years to attain.
What makes this all the more remarkable is that this rapid growth was not achieved in an attractive industry. It was in a declining industry in which traditional strategic analysis pointed to limited potential for growth. Supplier power on the part of star performers was strong. So was buyer power? From the perspective of competition-based strategy, then, the circus industry appeared unattractive.
Another compelling aspect of Cirque du Soleil's success is that it did not win by taking customers from the already shrinking demand for the circus industry, which historically catered to children. Cirque du Soleil did not compete with Ringling Brothers and Barnum & Bailey's Circus to make this happen. Instead it created uncontested new market space that made the competition irrelevant. It appealed to a whole new group of customers - adults and corporate clients prepared to pay a price that is several times as expensive as traditional circuses for their unprecedented entertainment experience. Significantly, one of the first Cirque productions was titled "We Reinvent the Circus".
Cirque du Soleil succeeded because it realized that to win in the future, companies must stop competing with each other. The only way to beat the competition is to stop trying to beat the competition.
In a brief article in Fast Company, Renee Mauborgne, the co-author of Blue Ocean Strategy, says companies can do what Cirque du Soleil did by following certain guidelines.
- Water, water, everywhere.
- You don't have to compete in a red ocean of bloody competition. Even exhausted industries -- like the circus can be reinvented.
- Don't swim with the school.
- Quit benchmarking the competition or setting your strategic agenda in the context of theirs.
- Find new ponds to fish.
- Don't assume your current customers have the insights you need to rethink your strategy. Look to non-customers instead.
- Cut bait on costs.
- Put as much emphasis on what you can eliminate as on what you can create.
Tuesday, July 24, 2007
The Private Life Of Henry VIII.
Memorable quote (s) from the movie:
King Henry VIII (Charles Laughton): Diplomacy? Diplomacy, my foot! I'm an Englishman -- I can't say one thing and mean another. What I can do is to build ships, ships, and then more ships!
Thomas Cromwell (Franklin Dyall): You mean, double the fleet?
King Henry VIII (Charles Laughton): Treble it. Fortify Dover. Rule the sea.
Thomas Cromwell (Charles Laughton): To do this will cost us money, sire.
King Henry VIII (Charles Laughton): To leave it undone will cost us England.
King Henry VIII (Charles Laughton): Diplomacy? Diplomacy, my foot! I'm an Englishman -- I can't say one thing and mean another. What I can do is to build ships, ships, and then more ships!
Thomas Cromwell (Franklin Dyall): You mean, double the fleet?
King Henry VIII (Charles Laughton): Treble it. Fortify Dover. Rule the sea.
Thomas Cromwell (Charles Laughton): To do this will cost us money, sire.
King Henry VIII (Charles Laughton): To leave it undone will cost us England.
Biopics Mix Shticks, Kitsch
Peter Plagens writes about movie makers love to dramatise the lives of famous artists + the boom in sub-genre (s) + other viewpoints @ http://artnews.com/issues/article.asp?art_id=2167
A Singapore Jeweler’s Nightmare Scenario
Chaim Even-Zohar writes about David Rasif & Partners, a law firm in Singapore, the police, the diamond market + other viewpoints @ http://www.idexonline.com/portal_FullEditorial.aspTextSearch=&KeyMatch=0&id=25869
Cosmetics And Gem Materials
(via The Journal of Gemmology, Vol. IX, No.8, October 1964) R Webster writes:
Turquoise and jade
Most turquoise has been treated in some way to improve the color and substances used for this treatment may be affected when cosmetic preparations get on to the surface of the stone. Even good colored non-treated turquoise may be affected by certain cosmetics. Robert Crowningshield refers to a case in which turquoise had discolored, apparently from the effects of cosmetics. There has been no report that jades have been affected by beauty preparations, but as jadeite can be dyed, deleterious effects could conceivably occur with this material.
Cosmetics And Gem Materials (continued)
Turquoise and jade
Most turquoise has been treated in some way to improve the color and substances used for this treatment may be affected when cosmetic preparations get on to the surface of the stone. Even good colored non-treated turquoise may be affected by certain cosmetics. Robert Crowningshield refers to a case in which turquoise had discolored, apparently from the effects of cosmetics. There has been no report that jades have been affected by beauty preparations, but as jadeite can be dyed, deleterious effects could conceivably occur with this material.
Cosmetics And Gem Materials (continued)
Hypersthene
Chemistry: Form of Enstatite, with increased iron content, usually opaque.
Crystal system: Orthorhombic; rarely short prismatic crystals; lamellar masses common.
Color: Opaque; gem varieties dark brown with coppery iridescence; hypersthene enstatite: transparent brown.
Hardness: 5 - 6
Cleavage: Good: in 1 direction.
Specific gravity: 3.4 – 3.5
Refractive index: 1.6 – 1.79; 1.673 – 1.731; Biaxial negative (optic sign changes along the series); 0.014
Luster: Vitreous, pearly or silky.
Dispersion: Low
Dichroism: Pinkish to greenish.
Occurrence: Igneous and metamorphic, also from meteorites; Norway, Greenland, Germany, USA, Mexico.
Notes
Also called ferrohypersthene; varieties include bronzite; spectral line at 506nm and 547nm; cabochon, slab.
Crystal system: Orthorhombic; rarely short prismatic crystals; lamellar masses common.
Color: Opaque; gem varieties dark brown with coppery iridescence; hypersthene enstatite: transparent brown.
Hardness: 5 - 6
Cleavage: Good: in 1 direction.
Specific gravity: 3.4 – 3.5
Refractive index: 1.6 – 1.79; 1.673 – 1.731; Biaxial negative (optic sign changes along the series); 0.014
Luster: Vitreous, pearly or silky.
Dispersion: Low
Dichroism: Pinkish to greenish.
Occurrence: Igneous and metamorphic, also from meteorites; Norway, Greenland, Germany, USA, Mexico.
Notes
Also called ferrohypersthene; varieties include bronzite; spectral line at 506nm and 547nm; cabochon, slab.
Monday, July 23, 2007
Is FinCEN’s AML/CFT Jewelry Rule Non-Compliant With International Standards?
Chaim Even-Zohar writes about the lack of harmonization of anti-money laundering rules among the key players + various interpretations by the government, diamond and jewelry sector + other viewpoints @ http://www.idexonline.com/portal_FullEditorial.asp?TextSearch=&KeyMatch=0&id=25907
Botswana Govt 'Own Worst Enemy' In dealing With San Issue
Martin Creamer writes about relocation of the Koisan, the bushmen + De Beer's commitment for near-mine communities + the economic position of the government + other viewpoints @ http://www.miningweekly.co.za/article.php?a_id=112985
Why Diamonds Are For The Long-term
(via Moneyweek) Garry White writes @ ‘Garry Writes’, his views on specific recommendations in the resource, infrastructure and biotech sectors via Outstanding Investments
Cosmetics And Gem Materials
2007: I stumbled upon this article during my research. It's an excellent article on cosmetics and the after-effects on pearls and other gem materials.
(via The Journal of Gemmology, Vol. IX, No.8, October 1964) R Webster writes:
Little has been recorded in literature of the possible effects on certain types of gem materials and pearls by the action of cosmetics used in beauty treatments, despite the fact that the embellishment of the natural appearance of women, and men, by the application of various preparations of mineral, animal and vegetable nature have been used since prehistoric times. The extensive use of the modern artificially made products used in beauty treatments today makes consideration of their effects of some importance.
It is quite clear that no harm will come to those gemstones cut from single crystals, except the greasy components of some cosmetics may adhere to the setting and backs of the stones causing them to lose their brilliancy. This, of course, is most important with diamond, a stone which collects grease so readily, and whose optical properties depend so much on the total internal reflection of light from the rear facets. Periodical cleaning is the answer here, and as this should be done anyway, there is no problem.
Those gem materials which are to some extent porous (and, indeed, these are the gems which can be artificially colored by stain or dye) are obviously those most likely to be adversely affected by the haphazard use of various cosmetic preparations. The most important of such gems are pearl, turquoise, opal and jade, and possibly agate and coral. Pearls are the most likely to suffer damage owing to the nature of their structure and to the fact that in the case of necklets especially, and to some extent earrings, they, when worn lie close to the skin or hair.
When it is realized that cosmetic preparations cover such fields as hair dyes and bleaches, depilatories, skin creams and face powders, hair-setting lotions and sprays, as well as eye shadow, lipstick and nail varnishes, and that each manufacturer has a different formula for his various products, it is obvious that any complete investigation would need the full time services of several workers. This, from economic considerations alone, would be out of the question. Some experiments and some actual cases which have been investigated and which have been reported from other workers are here recorded.
Pearls
Experience has shown that there are two distinct ways in which cosmetics can affect pearls. These are surface contamination and contamination which has worked inwardly through the string canal.
Surface contamination mostly occurs through the use of hair-setting sprays, perspiration deodorant sprays, and atomized perfumes. Hair-setting sprays often contain a synthetic cellulose derivative, such as methyl cellulose, and this, if used when pearls are worn, may give a coating of lacquer to them. Such an accidental lacquering, as has been shown by experiment, so coats the pearls that a pin drawn across the surface will dig up this coating in a similar manner to the effect shown when a pin is pressed against a solid glass type imitation pearl. Further, this coating tends to mask the suture marks, that is the overlapping edges of the aragonite platelets, and this also tends to give the impression that one is dealing with an imitation pearl.
When this extraneous coating ages, or has collected on the pearls rather as droplets than as a complete covering, the coating may peel or flake off and give the impression that it is the pearls that are flaking away. It is well for the jeweler to be mindful of this, as it has not been unknown for a customer to complain of this flaking of her pearls.
The second type of contamination, inwardly, may be illustrated by an actual case where an investigation was carried out. Briefly, a cultured pearl necklet was restrung by a jeweler on behalf of a customer and after about three months had elapsed the lady brought the necklet back and complained that since the pearls had been restrung a number of pearls had turned to a blackish color. The jeweler’s assistant who saw the lady fully agreed that some of the pearls had blackened and asked her to call again and discuss the matter with the manager. Instead of so doing the lady took the necklet to another jeweler, who had previously valued the necklet for insurance purposes. As would be expected the value now placed upon the necklet was considerably less than before, whereupon the indignant lady took the pearls to the local police station and lodged a complaint against the first jeweler.
The police interviewed the jeweler and suggested that a laboratory investigation should be made. The necklet, now in pieces, for the police had cut from the necklet all the blackened pearls, came into the hands of the writer for an investigation as to the cause of the blackening of the pearls. From previous experiments it was known that some pearls appear to darken by possible sulphiding of a metallic compound, which may have adventitiously been taken up by the organic part of the pearl, or by dirty grease entering the pearl through the stringing canal. There is a further, but unlikely, contingency that silver nitrate, which is used in some hair dyes, might be the activating factor, just as it is used for dyeing pearls black.
Examination of the string of the necklet under investigation showed some grease to be present, and that the snap itself was covered by grease, and to such an extent that one of the diamonds set in it was completely covered and could not be seen. Grease was evidently the answer here, but for completeness of the investigation a test for sulphiding was carried out. This gave a negative result.
Some of the discolored pearls were then degreased by using a Soxhlet extraction apparatus. After this treatment the pearls were found to be much whiter, and grease was recovered from the solvent used for the degreasing.
What happened here was that grease, presumably from cosmetic creams, had entered, by capillary attraction, along the stringing canal and up and around the discontinuation layer between the bead nucleus and the outer nacreous layer. The grease had darkened, owning to ageing and admixture with dirt, and this showed through the translucent pearly outside layer and make the pearls appear dark colored.
(continued)
(via The Journal of Gemmology, Vol. IX, No.8, October 1964) R Webster writes:
Little has been recorded in literature of the possible effects on certain types of gem materials and pearls by the action of cosmetics used in beauty treatments, despite the fact that the embellishment of the natural appearance of women, and men, by the application of various preparations of mineral, animal and vegetable nature have been used since prehistoric times. The extensive use of the modern artificially made products used in beauty treatments today makes consideration of their effects of some importance.
It is quite clear that no harm will come to those gemstones cut from single crystals, except the greasy components of some cosmetics may adhere to the setting and backs of the stones causing them to lose their brilliancy. This, of course, is most important with diamond, a stone which collects grease so readily, and whose optical properties depend so much on the total internal reflection of light from the rear facets. Periodical cleaning is the answer here, and as this should be done anyway, there is no problem.
Those gem materials which are to some extent porous (and, indeed, these are the gems which can be artificially colored by stain or dye) are obviously those most likely to be adversely affected by the haphazard use of various cosmetic preparations. The most important of such gems are pearl, turquoise, opal and jade, and possibly agate and coral. Pearls are the most likely to suffer damage owing to the nature of their structure and to the fact that in the case of necklets especially, and to some extent earrings, they, when worn lie close to the skin or hair.
When it is realized that cosmetic preparations cover such fields as hair dyes and bleaches, depilatories, skin creams and face powders, hair-setting lotions and sprays, as well as eye shadow, lipstick and nail varnishes, and that each manufacturer has a different formula for his various products, it is obvious that any complete investigation would need the full time services of several workers. This, from economic considerations alone, would be out of the question. Some experiments and some actual cases which have been investigated and which have been reported from other workers are here recorded.
Pearls
Experience has shown that there are two distinct ways in which cosmetics can affect pearls. These are surface contamination and contamination which has worked inwardly through the string canal.
Surface contamination mostly occurs through the use of hair-setting sprays, perspiration deodorant sprays, and atomized perfumes. Hair-setting sprays often contain a synthetic cellulose derivative, such as methyl cellulose, and this, if used when pearls are worn, may give a coating of lacquer to them. Such an accidental lacquering, as has been shown by experiment, so coats the pearls that a pin drawn across the surface will dig up this coating in a similar manner to the effect shown when a pin is pressed against a solid glass type imitation pearl. Further, this coating tends to mask the suture marks, that is the overlapping edges of the aragonite platelets, and this also tends to give the impression that one is dealing with an imitation pearl.
When this extraneous coating ages, or has collected on the pearls rather as droplets than as a complete covering, the coating may peel or flake off and give the impression that it is the pearls that are flaking away. It is well for the jeweler to be mindful of this, as it has not been unknown for a customer to complain of this flaking of her pearls.
The second type of contamination, inwardly, may be illustrated by an actual case where an investigation was carried out. Briefly, a cultured pearl necklet was restrung by a jeweler on behalf of a customer and after about three months had elapsed the lady brought the necklet back and complained that since the pearls had been restrung a number of pearls had turned to a blackish color. The jeweler’s assistant who saw the lady fully agreed that some of the pearls had blackened and asked her to call again and discuss the matter with the manager. Instead of so doing the lady took the necklet to another jeweler, who had previously valued the necklet for insurance purposes. As would be expected the value now placed upon the necklet was considerably less than before, whereupon the indignant lady took the pearls to the local police station and lodged a complaint against the first jeweler.
The police interviewed the jeweler and suggested that a laboratory investigation should be made. The necklet, now in pieces, for the police had cut from the necklet all the blackened pearls, came into the hands of the writer for an investigation as to the cause of the blackening of the pearls. From previous experiments it was known that some pearls appear to darken by possible sulphiding of a metallic compound, which may have adventitiously been taken up by the organic part of the pearl, or by dirty grease entering the pearl through the stringing canal. There is a further, but unlikely, contingency that silver nitrate, which is used in some hair dyes, might be the activating factor, just as it is used for dyeing pearls black.
Examination of the string of the necklet under investigation showed some grease to be present, and that the snap itself was covered by grease, and to such an extent that one of the diamonds set in it was completely covered and could not be seen. Grease was evidently the answer here, but for completeness of the investigation a test for sulphiding was carried out. This gave a negative result.
Some of the discolored pearls were then degreased by using a Soxhlet extraction apparatus. After this treatment the pearls were found to be much whiter, and grease was recovered from the solvent used for the degreasing.
What happened here was that grease, presumably from cosmetic creams, had entered, by capillary attraction, along the stringing canal and up and around the discontinuation layer between the bead nucleus and the outer nacreous layer. The grease had darkened, owning to ageing and admixture with dirt, and this showed through the translucent pearly outside layer and make the pearls appear dark colored.
(continued)
Howlite
Chemistry: Silico-borate of calcium.
Crystal system: Monoclinic; massive; compact nodules.
Color: Semi translucent to opaque; white material veined with dark gray or black.
Hardness: 3.5
Cleavage: -
Specific gravity: 2.52 (2.52 – 2.57)
Refractive index: 1.53 mean; aggregate.
Luster: Vitreous to sub-vitreous.
Dispersion: -
Dichroism: -
Occurrence: USA
Notes
Ornamental material; frequently dyed blue (turquoise, lapis); less often other colors (coral, jade); identification based on magnification, appearance (texture, color, structural markings); look for dye concentrations in cracks and grain boundaries; color, may be unstable; fluorescence: brownish yellow (short wave); some Californian material may fluoresce orange (long wave); cabochon, beads, carvings.
Crystal system: Monoclinic; massive; compact nodules.
Color: Semi translucent to opaque; white material veined with dark gray or black.
Hardness: 3.5
Cleavage: -
Specific gravity: 2.52 (2.52 – 2.57)
Refractive index: 1.53 mean; aggregate.
Luster: Vitreous to sub-vitreous.
Dispersion: -
Dichroism: -
Occurrence: USA
Notes
Ornamental material; frequently dyed blue (turquoise, lapis); less often other colors (coral, jade); identification based on magnification, appearance (texture, color, structural markings); look for dye concentrations in cracks and grain boundaries; color, may be unstable; fluorescence: brownish yellow (short wave); some Californian material may fluoresce orange (long wave); cabochon, beads, carvings.
Coffee Grading vs Colored Stone Grading
(via Coffee Review) Retailers may also qualify coffee labels by grade name. Grading is a device for controlling the quality of an agricultural commodity so that buyer and seller can do business without personally examining every lot sold. Coffee grading terminology is, unfortunately, varied and obscure. Every coffee-growing country has its own set of terms, and few are distinguished by logical clarity. Kenya AA is an exception: Clearly AA is better than A or B. But though the Colombian terms excelso and supremo are both laudatory, one could hardly determine by reason alone that supremo is the highest grade of Colombian coffee, and excelso a more comprehensive grade consisting of a mixture of supremo and the less desirable extra grade. Although we may be aware that altitude is a prime grading factor in Central American coffees, one could hardly guess without coaching that strictly hard bean refers to Guatemalan coffees grown at altitudes of 4,500 to 5,000 feet, and hard bean to those at 4,000 to 4,500 feet. The higher the altitude, the slower-maturing the bean, and the harder and denser its substance--hence hard bean.
Comparing colored stones with coffee: There are similarities. There are no internationally accepted systematic colored stone grading system in the world yet, with many people in the gem trade opposing to its introduction. Many in the gem industry overlook the advantages of having a systematic colored stone grading system. The benefits are increased consumer confidence and sales. In order to develop a colored stone grading system, one need to create a simple language useful for easy communication so that the relative value can be determined by the market + the consumers benefit from it because of its simplicity.
Colored gemstone dealers have their own grading system (s), and most use terms such as AAA, AA, A, BBB, BB, B, CCC, CC, C and so on. Dealers may understand the gradation but consumers don't. There is also a link between the coffee beans sources and rock types. Like the origin of the coffee beans, rock types of gemstones does play a major role in understanding the color variances of high value stones such as diamonds, rubies (basalt vs marble hosted rocks), sapphires (basalt vs marble hosted rocks, emeralds (hydrothermal vs pegmatite vs metamorphic associations), tourmalines (pegmatite) and other colored stones. Though the concept may not be new to practising gemologists, its application via gem testing/grading laboratories could make a big difference, if used appropriately.
Comparing colored stones with coffee: There are similarities. There are no internationally accepted systematic colored stone grading system in the world yet, with many people in the gem trade opposing to its introduction. Many in the gem industry overlook the advantages of having a systematic colored stone grading system. The benefits are increased consumer confidence and sales. In order to develop a colored stone grading system, one need to create a simple language useful for easy communication so that the relative value can be determined by the market + the consumers benefit from it because of its simplicity.
Colored gemstone dealers have their own grading system (s), and most use terms such as AAA, AA, A, BBB, BB, B, CCC, CC, C and so on. Dealers may understand the gradation but consumers don't. There is also a link between the coffee beans sources and rock types. Like the origin of the coffee beans, rock types of gemstones does play a major role in understanding the color variances of high value stones such as diamonds, rubies (basalt vs marble hosted rocks), sapphires (basalt vs marble hosted rocks, emeralds (hydrothermal vs pegmatite vs metamorphic associations), tourmalines (pegmatite) and other colored stones. Though the concept may not be new to practising gemologists, its application via gem testing/grading laboratories could make a big difference, if used appropriately.
Treated Topaz: Bangkok
For some time there have been a significant increase in the volume of orange + reddish + pinkish brown topaz in the Bangkok market, and there are all sorts of rumors about its origin. Gem dealers have their own tales; some say they are Brazilian, while others claim they are African, Burmese and so on. The stones are not expensive so buyers from all corners of the world are buying them so that they can sell the stones on the internet, but many are not disclosing the color stability of the stones. And the fact of the matter is most specimens are unstable and upon exposure to direct sunlight for several hours, they fade to near colorless. Buyer beware!
Sunday, July 22, 2007
Blood Diamonds
(via History Channel) Diamonds are symbols of wealth, elegance and love around the world. But in several African nations, they have been a means to power, a reason to terrorize millions of innocent civilians, and may have even helped finance some of the world's most brutal terrorists. The human cost of the illicit global diamond trade is examined in the provocative documentary BLOOD DIAMONDS only on THE HISTORY CHANNEL @ http://www.history.com/minisites/blooddiamonds
I think it's one of the best documentary on blood diamonds.
I think it's one of the best documentary on blood diamonds.
The Scientific Gemmologist
2007: I like the snowcap on a mountain analogy. Gemology is gradually morphing, but the basic tenets remains the same. Today there are new analytical instruments for gemologist (s) to analyze and interpret, at a cost, but you still need a third eye to identify unknown gemstones with basic instruments. Today consumers want simplicity. They have no time nor the ability to understand the chemical, physical and optical properites of gemstones + experience alone is not enough; you need that 'otherness', that special feel for gemstones. It's a gift from the gods, and only a few have those skills.
(via The Journal of Gemmology, Vo.IX. No.6, April 1964) G V Axon writes:
The purpose of this article is to examine the current status of gemology, to make a few comments thereon, and to report a minor research project on distinguishing man-made from natural crystals.
There seems to be a general feeling among active gemologists that gemology as a science is somehow up against a brick wall. There is a great deal of useful, interesting, and informative writing, but there is a tendency to spread the well-known techniques over a greater area instead of developing new techniques to deal with problems which currently are without solution or present considerable difficulty even to experienced and highly regarded gemologists.
Thus to a newcomer, such as this writer, there seems a tendency to emphasize the obvious, to repeat the well-known, and to avoid facing up to the fact that gemology as a science needs a new structure in its intellectual basis—perhaps, in fact, a radical decision to recognize the existence of two types of gemologists. These are, of course, the ordinary trade gemologists and those who by reason of their training, interest, and experience are, in fact, scientific gemologists whether they are in the trade or not.
Gemology, today, is rather like a snowcap on a mountain. It is the most interesting part of the mountain. It sparkles in the sun like so many diamonds. It attracts mineralogists and geologists quite apart from members of the trade and trade laboratories, and hobbyists. One can well understand its attraction. But so many of those interested in the snowcap have never bothered to understand why the snow is there, and why it stays there. They are content to play with the snow and have a good time. They are simply not interested in understanding the massive structure on which the snowcap rests.
The result is that many in gem field are walking around on intellectual stilts and might topple over at any time. They would be hard put to explain why no chromium is found in the feldspars, and why fluorite and hydroxyl ions are found in silicate minerals such as topaz and tourmaline. This is not to criticize: it is merely to point out that gems are delightful things to study and handle, and that quite apart from this the vast majority of gemologists are not engaged in any fulltime capacity in the gem field. Even those who have qualified seldom dig deeper into the intellectual basis of gemology.
Of equal importance is the fact that gemology has long been regarded as a step-child of mineralogy. The basic reason for this, of course, is that the most valuable substances used as gems are minerals, and that, without minerals, gemology and the jewelry industry would be very much the poorer.
Yet since time immemorial many of the substances used in jewelry have been man-made. Ancient civilizations have yielded very many examples of man-made gems: they have yielded only a few valuable natural gemstones. Yet because the natural gemstones are the flowers of the mineral kingdom, gemology has had to be content with playing second fiddle to mineralogy.
Plainly, this is no longer acceptable. It is not only that natural gemstones, especially the finest, are becoming increasingly rare, but that the substances used as gems are increasingly varied and increasingly difficult to distinguish. Today, gemologists, having relied probably for far too long on mineralogists, are faced with having to reconstruct the intellectual basis of their profession. The problem is basically one for the scientific gemologists.
Clearly, the first approach must be to shift the intellectual basis of gemology away from the glittering and inviting snowcap to the uninviting and less glamorous rock base. There is a need for a far more fundamental approach to the study of gemology. It should surely start with the formation of the universe, the development of the elements, the formation of the earth, and how the elements came together to form various substances known as rocks, minerals and crystals.
As some gem material is of organic origin, there should be at least some attempt to explain, as far as possible, the development of organic from inorganic life, and the organic structure of the various organic gem materials.
Today, the gemologist is faced not only with a wide variety of man-made substances used as gems, but also with an increasingly wide range of man-made crystals. Only those gemologists who have had time to look into this growing field of man-made crystals can fully appreciate its extent. Not only is there a vast variety of crystals in element and compound form, but many of these crystals may be doped by other substances for various scientific and industrial purposes. It would be almost impossible for gemologists to keep up with the developments even if they had the time. As for distinguishing the man-made from the natural crystal material, it will obviously become more rather than less acute.
Even though many of these man-grown crystals are not suitable for use as gems, the intellectual problem remains. In the United States, especially, there are thousands of amateur lapidaries who are not too willing to test their skills on anything they can put their hands on, from man-grown crystals to coprolites. Sooner or later, these curiosities find their way to the gem trade laboratory.
It was with the intention of discovering any new techniques that inquiries were made of some two dozen crystal-growing firms and scientists in the United States. The idea sprang from a comment on Carbon 14 in correspondence to this writer from J R Jones of Sydney, Australia. It was thought that if techniques were so advanced in one field, perhaps similar techniques (without destroying the material, of course) could be applied to the gem field. There must surely be some differences between natural crystals, say sixty million years old, and crystals being grown this minute in factories and laboratories.
The enquiries yielded a meager harvest. Some of the comments received are listed below mainly out of curiosity. Only in one case, dealt with later, was a basically new idea (at least, new to this writer) advanced.
1. Synthetic quartz crystals cost about twelve times as much as natural quartz.
2. Synthetic quartz crystals often have complete faces whereas natural quartz crystals often have many faces missing.
3. Synthetic crystals are much purer as a rule.
4. Synthetic production techniques often use no water, whereas natural crystals have often been produced by hydrothermal forces. Thus they contain microscopic water pockets (partially filled vacuoles). Unfortunately, analysis techniques destroy the material.
5. The majority of man-made quartz is grown in a sodium hydroxide or sodium carbonate solution. Thus the sodium content is usually higher in the synthetic.
6. Synthetics show fewer absorptions when analyzed by infra-red spectrographic methods.
7. X-ray analysis, neutron activation, and electron and neutron diffraction, were also given as possible methods.
8. X-ray diffraction topography will show a greater concentration of dark lines in the synthetic when measured against a natural crystal. Spectrographic analysis, which requires the grinding of some of the material, usually shows a greater concentration of some elements in the synthetic.
Of particular interest is the electron paramagnetic resonance spectroscopy (EPR) developed by Varian Associates, Palo Alto, California, USA. Unfortunately, the instrument costs some $30000, and the fee quoted tentatively for each spectrum was $25. Although one test may not suffice for full identification, such a test may be able to establish that a gemstone was not natural.
The basis of EPR lies in minute chemical and structural anomalies. The extremely complex instrument is an extremely sensitive, non-destructive way of detecting impurity levels in crystals. A synthetic would be relatively pure. The result is basically a graph showing straight and jagged lines, hills, and valleys, which vary according to the structural perfection and molecular structure of the material analyzed.
According to the material supplied by the company, it is now possible to use the magnetic properties of electrons (as well as of nuclei) to reveal chemical structure and bonding characteristics.
Just as nuclei have charge, mass, angular momenta and magnetic moments, so do electrons, and it is upon this that EPR depends. If the electron has not only an intrinsic magnetic moment along its own spin axis, but also one associated with its circulation in an atomic orbit, the electron will possess a total magnetic moment equal to the vector sum of these magnetic moments. The ratio of this total magnetic moment to the spin value is constant for a given atom and environment, and is called the gyromagnetic ratio or spectroscopic splitting factor for that particular electron. The fact that these ratios differ for various atoms and environments and the fact that local magnetic fields depend on the structure of matter permit the spectral separation and study according to the method of electron paramagnetic resonance spectroscopy.
It must be emphasized that not all atoms and molecules are susceptible to such study. There must be a resultant electronic magnetic moment associated with the atom or molecule under investigation; for example, effects may be observed for electrons in unfilled conduction bands, transition element ions, odd molecules and free radicals, biradicals, color centers, radiation damage sites, impurities in semi-conductors, and triplet electronic states.
The principal components of the EPR spectrometer are an electromagnet, a sweep generator, a stable microwave oscillator, a resonant cavity, a bolometer or crystal detector for demodulating the microwave power reflected from the resonant cavity (for the sample), an audio amplifier and a phase-sensitive detector, and a graphic recorder.
Possibly, this instrument has not been used much, if at all, in gemology, but the descriptions given above may plant a seed in minds better prepared in gemology than that of this writer. Certainly the idea is of great theoretical interest in the crystal field, and it seems to offer possibilities to the gemologist. It is becoming quite impossible to determine, by ordinary gemological methods, the nature of all crystals. If the synthetics and man-made can be weeded out and certified as man-made, it should then at least be easier to concentrate on determining the nature of the natural crystal material.
(via The Journal of Gemmology, Vo.IX. No.6, April 1964) G V Axon writes:
The purpose of this article is to examine the current status of gemology, to make a few comments thereon, and to report a minor research project on distinguishing man-made from natural crystals.
There seems to be a general feeling among active gemologists that gemology as a science is somehow up against a brick wall. There is a great deal of useful, interesting, and informative writing, but there is a tendency to spread the well-known techniques over a greater area instead of developing new techniques to deal with problems which currently are without solution or present considerable difficulty even to experienced and highly regarded gemologists.
Thus to a newcomer, such as this writer, there seems a tendency to emphasize the obvious, to repeat the well-known, and to avoid facing up to the fact that gemology as a science needs a new structure in its intellectual basis—perhaps, in fact, a radical decision to recognize the existence of two types of gemologists. These are, of course, the ordinary trade gemologists and those who by reason of their training, interest, and experience are, in fact, scientific gemologists whether they are in the trade or not.
Gemology, today, is rather like a snowcap on a mountain. It is the most interesting part of the mountain. It sparkles in the sun like so many diamonds. It attracts mineralogists and geologists quite apart from members of the trade and trade laboratories, and hobbyists. One can well understand its attraction. But so many of those interested in the snowcap have never bothered to understand why the snow is there, and why it stays there. They are content to play with the snow and have a good time. They are simply not interested in understanding the massive structure on which the snowcap rests.
The result is that many in gem field are walking around on intellectual stilts and might topple over at any time. They would be hard put to explain why no chromium is found in the feldspars, and why fluorite and hydroxyl ions are found in silicate minerals such as topaz and tourmaline. This is not to criticize: it is merely to point out that gems are delightful things to study and handle, and that quite apart from this the vast majority of gemologists are not engaged in any fulltime capacity in the gem field. Even those who have qualified seldom dig deeper into the intellectual basis of gemology.
Of equal importance is the fact that gemology has long been regarded as a step-child of mineralogy. The basic reason for this, of course, is that the most valuable substances used as gems are minerals, and that, without minerals, gemology and the jewelry industry would be very much the poorer.
Yet since time immemorial many of the substances used in jewelry have been man-made. Ancient civilizations have yielded very many examples of man-made gems: they have yielded only a few valuable natural gemstones. Yet because the natural gemstones are the flowers of the mineral kingdom, gemology has had to be content with playing second fiddle to mineralogy.
Plainly, this is no longer acceptable. It is not only that natural gemstones, especially the finest, are becoming increasingly rare, but that the substances used as gems are increasingly varied and increasingly difficult to distinguish. Today, gemologists, having relied probably for far too long on mineralogists, are faced with having to reconstruct the intellectual basis of their profession. The problem is basically one for the scientific gemologists.
Clearly, the first approach must be to shift the intellectual basis of gemology away from the glittering and inviting snowcap to the uninviting and less glamorous rock base. There is a need for a far more fundamental approach to the study of gemology. It should surely start with the formation of the universe, the development of the elements, the formation of the earth, and how the elements came together to form various substances known as rocks, minerals and crystals.
As some gem material is of organic origin, there should be at least some attempt to explain, as far as possible, the development of organic from inorganic life, and the organic structure of the various organic gem materials.
Today, the gemologist is faced not only with a wide variety of man-made substances used as gems, but also with an increasingly wide range of man-made crystals. Only those gemologists who have had time to look into this growing field of man-made crystals can fully appreciate its extent. Not only is there a vast variety of crystals in element and compound form, but many of these crystals may be doped by other substances for various scientific and industrial purposes. It would be almost impossible for gemologists to keep up with the developments even if they had the time. As for distinguishing the man-made from the natural crystal material, it will obviously become more rather than less acute.
Even though many of these man-grown crystals are not suitable for use as gems, the intellectual problem remains. In the United States, especially, there are thousands of amateur lapidaries who are not too willing to test their skills on anything they can put their hands on, from man-grown crystals to coprolites. Sooner or later, these curiosities find their way to the gem trade laboratory.
It was with the intention of discovering any new techniques that inquiries were made of some two dozen crystal-growing firms and scientists in the United States. The idea sprang from a comment on Carbon 14 in correspondence to this writer from J R Jones of Sydney, Australia. It was thought that if techniques were so advanced in one field, perhaps similar techniques (without destroying the material, of course) could be applied to the gem field. There must surely be some differences between natural crystals, say sixty million years old, and crystals being grown this minute in factories and laboratories.
The enquiries yielded a meager harvest. Some of the comments received are listed below mainly out of curiosity. Only in one case, dealt with later, was a basically new idea (at least, new to this writer) advanced.
1. Synthetic quartz crystals cost about twelve times as much as natural quartz.
2. Synthetic quartz crystals often have complete faces whereas natural quartz crystals often have many faces missing.
3. Synthetic crystals are much purer as a rule.
4. Synthetic production techniques often use no water, whereas natural crystals have often been produced by hydrothermal forces. Thus they contain microscopic water pockets (partially filled vacuoles). Unfortunately, analysis techniques destroy the material.
5. The majority of man-made quartz is grown in a sodium hydroxide or sodium carbonate solution. Thus the sodium content is usually higher in the synthetic.
6. Synthetics show fewer absorptions when analyzed by infra-red spectrographic methods.
7. X-ray analysis, neutron activation, and electron and neutron diffraction, were also given as possible methods.
8. X-ray diffraction topography will show a greater concentration of dark lines in the synthetic when measured against a natural crystal. Spectrographic analysis, which requires the grinding of some of the material, usually shows a greater concentration of some elements in the synthetic.
Of particular interest is the electron paramagnetic resonance spectroscopy (EPR) developed by Varian Associates, Palo Alto, California, USA. Unfortunately, the instrument costs some $30000, and the fee quoted tentatively for each spectrum was $25. Although one test may not suffice for full identification, such a test may be able to establish that a gemstone was not natural.
The basis of EPR lies in minute chemical and structural anomalies. The extremely complex instrument is an extremely sensitive, non-destructive way of detecting impurity levels in crystals. A synthetic would be relatively pure. The result is basically a graph showing straight and jagged lines, hills, and valleys, which vary according to the structural perfection and molecular structure of the material analyzed.
According to the material supplied by the company, it is now possible to use the magnetic properties of electrons (as well as of nuclei) to reveal chemical structure and bonding characteristics.
Just as nuclei have charge, mass, angular momenta and magnetic moments, so do electrons, and it is upon this that EPR depends. If the electron has not only an intrinsic magnetic moment along its own spin axis, but also one associated with its circulation in an atomic orbit, the electron will possess a total magnetic moment equal to the vector sum of these magnetic moments. The ratio of this total magnetic moment to the spin value is constant for a given atom and environment, and is called the gyromagnetic ratio or spectroscopic splitting factor for that particular electron. The fact that these ratios differ for various atoms and environments and the fact that local magnetic fields depend on the structure of matter permit the spectral separation and study according to the method of electron paramagnetic resonance spectroscopy.
It must be emphasized that not all atoms and molecules are susceptible to such study. There must be a resultant electronic magnetic moment associated with the atom or molecule under investigation; for example, effects may be observed for electrons in unfilled conduction bands, transition element ions, odd molecules and free radicals, biradicals, color centers, radiation damage sites, impurities in semi-conductors, and triplet electronic states.
The principal components of the EPR spectrometer are an electromagnet, a sweep generator, a stable microwave oscillator, a resonant cavity, a bolometer or crystal detector for demodulating the microwave power reflected from the resonant cavity (for the sample), an audio amplifier and a phase-sensitive detector, and a graphic recorder.
Possibly, this instrument has not been used much, if at all, in gemology, but the descriptions given above may plant a seed in minds better prepared in gemology than that of this writer. Certainly the idea is of great theoretical interest in the crystal field, and it seems to offer possibilities to the gemologist. It is becoming quite impossible to determine, by ordinary gemological methods, the nature of all crystals. If the synthetics and man-made can be weeded out and certified as man-made, it should then at least be easier to concentrate on determining the nature of the natural crystal material.
Hemimorphite
Chemistry: Zinc silicate
Crystal system: Orthorhombic; double termination, but of different orientation (hemimorphic); tabular and thin striated crystals; fan-shaped aggregates; massive material granular or fibrous, banded or stalactitic.
Color: Transparent to opaque; commonly banded blue or green; colorless or white, also violet, gray, yellow and brown.
Hardness: 4.5 - 5
Cleavage: Perfect: 1 direction; Fracture: brittle, conchoidal to sub-conchoidal.
Specific gravity: 3.4 – 3.5
Refractive index: 1.63 mean; 1.614 – 1.636; Biaxial positive; 0.022
Luster: Vitreous, silky to dull.
Dispersion: -
Dichroism: -
Occurrence: Secondary mineral in oxidation; oxidation zone of zinc containing ore bodies; Italy, Mexico, Namibia, Algeria.
Notes
Usually associated with smithsonite; massive may look like smithsonite, chrysocolla or turquoise; colorless (rare); crystals faceted for collectors; massive blue material cut cabochon.
Crystal system: Orthorhombic; double termination, but of different orientation (hemimorphic); tabular and thin striated crystals; fan-shaped aggregates; massive material granular or fibrous, banded or stalactitic.
Color: Transparent to opaque; commonly banded blue or green; colorless or white, also violet, gray, yellow and brown.
Hardness: 4.5 - 5
Cleavage: Perfect: 1 direction; Fracture: brittle, conchoidal to sub-conchoidal.
Specific gravity: 3.4 – 3.5
Refractive index: 1.63 mean; 1.614 – 1.636; Biaxial positive; 0.022
Luster: Vitreous, silky to dull.
Dispersion: -
Dichroism: -
Occurrence: Secondary mineral in oxidation; oxidation zone of zinc containing ore bodies; Italy, Mexico, Namibia, Algeria.
Notes
Usually associated with smithsonite; massive may look like smithsonite, chrysocolla or turquoise; colorless (rare); crystals faceted for collectors; massive blue material cut cabochon.
Saturday, July 21, 2007
Colored Stone Update
Colored stone markets are growing. The prices for top quality rubies are too expensive with supply getting difficult. Today Burma and Sri Lanka are the key sources for good quality colored stones + buying rubies and sapphires from the Burmese or Sri Lankan in their territory is not an easy task. They really know the world prices and bargain hard + they have also learned how to say No. Other colored stone species and varieties are also becoming popular. The prices for top quality Colombian emerald have increased more than 25%. Fancy sapphires are popular and selling well. Amethyst, citrine, garnet, tourmaline, topaz, ziron, feldspar have all become popular choices for regular markets + television and internet-based retailers have also helped to promote colored stones. They have made a significant impact, because they not only educate consumers by expanding the gemological vocabulary beyond the mainstream colored stones but also on pricing. Consumers have now become familiar with less known colored stones such as sphene, sphalerite, Paraiba-type tourmalines, zircon, peridot, spinel and much more + new treatments, synthetics and imitations. Unique designers have also adapted to the changing trends promoting colored stones. Consumers are gradually becoming like 'little Buddhas'.
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