(via Gemmology Queensland, Vol.5, No.3, March 2004)
For about a year, Thai gem merchants have been selling considerable amounts of ruby from a recently discovered alluvial source in central eastern Madagascar. The principal source of this ruby is an area about 15km south-west of the central coastal town of Vatomandry. Ruby from this deposit has several interesting features:
- A considerable proportion of the rough does not require heat treatment.
- Some of the ruby closely resembles premium Burmese ruby in color.
In the recently published July 2001 issue of The Journal of Gemmology (pp 409-416), Schwartz & Schemetzer have described the identifying features of this ruby. The authors research has revealed that although ruby from this deposit displays the conventional properties of ruby, their fluorescence was weak to medium for LWUV and inert to very weak for SWUV (due to their 0.1-0.7 wt% content of Fe³+).
Characteristic inclusions observed in specimens that had not been treated included:
- Twin lamellae oriented in two directions.
- Intersecting twin lamellae decorated by tube to needle-like masses of white boehmite particles.
- Short needles and twinned or elongated plate-like crystals of rutile that are oriented in three directions.
- No visible growth zoning.
- Clusters of small, colorless to whitish birefringent zircon crystals.
- A few large apatite crystals.
- Healed fractures of variable shapes.
Trace element analysis of Vatomandry ruby revealed that this ruby has a higher (0.1-0.7 wt%) iron content than Burmese ruby (0.005 wt%), and it contains more vanadium (0.005-0.07 wt %) that Thai-Cambodian ruby (0.01 wt%).
Further, the authors suggest that heat treatment of this ruby at low temperature (<1450°C) to remove any purplish overtone could be difficult to detect—particularly if the rubies only had rutile and clusters of zircon as their only inclusions.
The authors conclude that this ruby’s unique trace element chemistry, combined with its lack of growth zoning, short rutile needles, and clusters of small zircon, will allow its discrimination from ruby of similar color but differing provenance such as Burma and Thailand-Cambodia.
Saturday, April 14, 2007
Where Did Spectacles Come From?
(via Gemmology Queensland, Vol.4, No.11, November 2003 / IIS Newsletter 80/2003)
Apparently no visual instruments existed at the time of the ancient Egyptians, Greeks, or Romans. At least this view is supported by a letter written by a prominent Roman about 100 B.C in which he stressed his resignation to old age and his complaint that he could no longer read for himself, having instead to rely on his slaves. The Roman tragedian Seneca, born in about 4 B.C is alleged to have read all the books in Rome by peering at them through a glass globe of water to produce magnification. Nero used an emerald held up to his eye while he watched gladiators fight. This is not proof that the Romans had any idea about lenses, since it is likely that Nero used the emerald because of its green color, which filtered the sunlight. Ptolemy mentions the general principle of magnification; but the lenses then available were unsuitable for use in precise magnification.
The oldest known lens was found in the ruins of ancient Nineveh and was made of polished rock crystal, an inch and one-half in diameter. Aristophanes in ‘The Clouds’ refers to a glass for burning holes in parchment and also mentions the use of burning glasses for erasing writing from wax tablets. According to Pliny, physicians used them for cauterizing wounds. Around 1000 A.D the reading stone, what we know as a magnifying glass, was developed. It was a segment of a glass sphere that could be laid against reading material to magnify the letters. It enables presbyopic (short sighted) monks to read and was probably the first reading aid.
The Venetians learned how to produce glass for reading ‘stones’, and later they constructed lenses that could be held in a frame in front of the eyes instead of directly on the reading material. Spectacles as we know them, were invented some 700 hundred years ago, presumably in Northern Italy. The oldest complete specimens date from sometime around 1350 and were found in the excavation of a nunnery near Celle in Germany. The first glasses were made out of beryl, a semi-precious stone, from which glasses obtained their name in Germanic languages, where they are called bril or brille.
The first known artistic representation of eyeglasses was painted by Tommaso da Modena in 1352. He did a series of frescoes of brothers busily reading or copying manuscripts. One holds a magnifying glass, but another has glasses perched on his nose. Once Tommaso had established the precedent, other painters placed spectacles on the noses of all sorts of subjects, probably as a symbol of wisdom and respect.
The first spectacles had quartz lenses because optical glass had not been developed. The lenses were set into bone, metal or even leather mountings, often shaped like two small magnifying glasses with handles riveted together typically in an inverted V shape that could be balanced on the bridge of the nose. The use of spectacles spread from Italy to the Low Countries, Germany, Spain, and France. In England, a Spectacle Makers Company was formed in 1629; its coat of arms showed three pairs of spectacles and a motto: ‘A blessing to the aged’.
Benjamin Franklin in the 1780’s developed the bifocal. Later he wrote, “I therefore had formerly two pairs of spectacles, which I shifted occasionally, as in traveling I sometimes read, and often wanted to regard the prospects. Finding this change troublesome, and not always sufficiently ready, I had the glasses cut and a half of each kind associated in the same circle. By this means, as I wear my own spectacles constantly, I have only to move my eyes by or down, as I want to see distinctly far or near, the proper glasses being always ready.” Modern eyeglass frames can be made of almost any material, including ivory, tortoiseshell, wood, metal, and plastic.
Apparently no visual instruments existed at the time of the ancient Egyptians, Greeks, or Romans. At least this view is supported by a letter written by a prominent Roman about 100 B.C in which he stressed his resignation to old age and his complaint that he could no longer read for himself, having instead to rely on his slaves. The Roman tragedian Seneca, born in about 4 B.C is alleged to have read all the books in Rome by peering at them through a glass globe of water to produce magnification. Nero used an emerald held up to his eye while he watched gladiators fight. This is not proof that the Romans had any idea about lenses, since it is likely that Nero used the emerald because of its green color, which filtered the sunlight. Ptolemy mentions the general principle of magnification; but the lenses then available were unsuitable for use in precise magnification.
The oldest known lens was found in the ruins of ancient Nineveh and was made of polished rock crystal, an inch and one-half in diameter. Aristophanes in ‘The Clouds’ refers to a glass for burning holes in parchment and also mentions the use of burning glasses for erasing writing from wax tablets. According to Pliny, physicians used them for cauterizing wounds. Around 1000 A.D the reading stone, what we know as a magnifying glass, was developed. It was a segment of a glass sphere that could be laid against reading material to magnify the letters. It enables presbyopic (short sighted) monks to read and was probably the first reading aid.
The Venetians learned how to produce glass for reading ‘stones’, and later they constructed lenses that could be held in a frame in front of the eyes instead of directly on the reading material. Spectacles as we know them, were invented some 700 hundred years ago, presumably in Northern Italy. The oldest complete specimens date from sometime around 1350 and were found in the excavation of a nunnery near Celle in Germany. The first glasses were made out of beryl, a semi-precious stone, from which glasses obtained their name in Germanic languages, where they are called bril or brille.
The first known artistic representation of eyeglasses was painted by Tommaso da Modena in 1352. He did a series of frescoes of brothers busily reading or copying manuscripts. One holds a magnifying glass, but another has glasses perched on his nose. Once Tommaso had established the precedent, other painters placed spectacles on the noses of all sorts of subjects, probably as a symbol of wisdom and respect.
The first spectacles had quartz lenses because optical glass had not been developed. The lenses were set into bone, metal or even leather mountings, often shaped like two small magnifying glasses with handles riveted together typically in an inverted V shape that could be balanced on the bridge of the nose. The use of spectacles spread from Italy to the Low Countries, Germany, Spain, and France. In England, a Spectacle Makers Company was formed in 1629; its coat of arms showed three pairs of spectacles and a motto: ‘A blessing to the aged’.
Benjamin Franklin in the 1780’s developed the bifocal. Later he wrote, “I therefore had formerly two pairs of spectacles, which I shifted occasionally, as in traveling I sometimes read, and often wanted to regard the prospects. Finding this change troublesome, and not always sufficiently ready, I had the glasses cut and a half of each kind associated in the same circle. By this means, as I wear my own spectacles constantly, I have only to move my eyes by or down, as I want to see distinctly far or near, the proper glasses being always ready.” Modern eyeglass frames can be made of almost any material, including ivory, tortoiseshell, wood, metal, and plastic.
Administratium
(via Gemmology Queensland, Vol.5, No.6, June 2004) Steve Sorrell writes:
The heaviest element known to science was recently discovered. The element, tentatively named Administratium , has no protons or electrons and thus has an atomic number 0. However, it does have 1 neutron, 125 assistant neutrons, 75 vice neutrons and 111 assistant vice neutrons, giving it an atomic mass of 312. These 312 particles are held together in the nucleus by a force that involves the continuous exchange of meson-like particles called morons.
Since it has no electrons, Administratium is inert. However, it can be detected chemically as it impedes every reaction with which it comes in contact. According to the discoverers, a tiny amount of Administratium caused one reaction to take over 4 days to complete when it would normally occur in less than one second.
Administratium has a normal half-life of approximately 3 years. At this time it doesn’t actually decay but instead undergoes reorganization in which assistant neutrons, vice neutrons, and assistant vice neutrons exchange places. Some studies have shown that the atomic mass actually increased after each reorganization.
Researchers at other laboratories indicated that Administratium occurs naturally in the atmosphere. It tends to concentrate at certain points such as universities, government agencies, large corporations, and schools. The element can be found in the newest, best-appointed and best-maintained buildings.
Scientists point out that Administratium is known to be toxic at any level of concentration and can easily destroy any productive reactions where it is allowed to accumulate. Attempts are being made to determine how Administratium can be controlled to prevent irreversible damage, but results are not promising.
The heaviest element known to science was recently discovered. The element, tentatively named Administratium , has no protons or electrons and thus has an atomic number 0. However, it does have 1 neutron, 125 assistant neutrons, 75 vice neutrons and 111 assistant vice neutrons, giving it an atomic mass of 312. These 312 particles are held together in the nucleus by a force that involves the continuous exchange of meson-like particles called morons.
Since it has no electrons, Administratium is inert. However, it can be detected chemically as it impedes every reaction with which it comes in contact. According to the discoverers, a tiny amount of Administratium caused one reaction to take over 4 days to complete when it would normally occur in less than one second.
Administratium has a normal half-life of approximately 3 years. At this time it doesn’t actually decay but instead undergoes reorganization in which assistant neutrons, vice neutrons, and assistant vice neutrons exchange places. Some studies have shown that the atomic mass actually increased after each reorganization.
Researchers at other laboratories indicated that Administratium occurs naturally in the atmosphere. It tends to concentrate at certain points such as universities, government agencies, large corporations, and schools. The element can be found in the newest, best-appointed and best-maintained buildings.
Scientists point out that Administratium is known to be toxic at any level of concentration and can easily destroy any productive reactions where it is allowed to accumulate. Attempts are being made to determine how Administratium can be controlled to prevent irreversible damage, but results are not promising.
The Monkey Puzzle Tree: Claimed Source Of Jet
(via Gemmology Queensland, Vol.5, No.6, June 2004)
The araucaria family (Araucariaceae) contains three remarkable genera of cone-bearing trees: Araucaria, Agathis, and Wollemia. They are tall trees native to forested regions of South America and Australia. In majestic size and beauty, they certainly rival the coniferous forests of North America and Eurasia. In fact, they are considered the southern counterpart of our northern pine forests. The type genus Araucaria is derived from ‘Arauco’, a region in central Chile where the Araucani Indians live. This is also the land of the ‘monkey puzzle’ tree (A. araucana), so named because the prickly, tangled branches would be difficult for a monkey to climb. Fossil evidence indicates that ancestral araucaria forests resembling the present day monkey puzzle date back to the age of dinosaurs. In fact, it has been suggested the tree’s armor of dagger-like leaves was designed to discourage enormous South American herbivorous dinosaurs, such as Argentinosaurus weighing and estimated 80 to 100 tons. Another ancient South American species called pino parana or parana pine (A. angustifolia) grows in southern Brazil and Argentina.
Any discussion of fossilized araucariads would be incomplete without mentioning a medieval gemstone called jet. Jet is a semi-precious gem excavated in Europe and formed by metamorphosis and anaerobic fossilization of araucaria wood buried under sediments in ancient seas. Ancestral forests that metamorphosed into jet date back to the Jurassic period, about 160 million years ago. They were similar to present day forests of monkey puzzle trees (Araucaria araucana) that grow in South America. Chemically, jet is hard, carbonized form of bituminous coal with a density similar to anthracite coal. Anthracite can be readily identified by its metallic luster. Jet takes a high polish and has been used for shiny black jewelry for thousands of years. It has a specific gravity of 1.3, almost as hard as the ironwood called lignum vitae (Guaiacum officinale). Jet became very popular during the mid 19th century England during the reign of Queen Victoria, and was often worn to ward off evil spirits and during times of mourning. In the first century AD, the Roman naturalist and writer Pliny described the magical and medicinal attributes of this beautiful mineral. The well-known analogy of ‘jet’ and ‘black’ was coined by William Shakespeare in his ‘black as jet’ from Henry VI part 2. One of the most famous areas for mining of Victorian jet is Whitby on the rugged Northeast coast of England. Although they are similar in hardness, anthracite has a metallic luster and jet is dull black. Jet takes a high polish and has been used in various carved jewelry, such as cameos and intaglios. The Victoria jet broach (circa 1890) was a popular item of jewelry during the 19th century.
The araucaria family (Araucariaceae) contains three remarkable genera of cone-bearing trees: Araucaria, Agathis, and Wollemia. They are tall trees native to forested regions of South America and Australia. In majestic size and beauty, they certainly rival the coniferous forests of North America and Eurasia. In fact, they are considered the southern counterpart of our northern pine forests. The type genus Araucaria is derived from ‘Arauco’, a region in central Chile where the Araucani Indians live. This is also the land of the ‘monkey puzzle’ tree (A. araucana), so named because the prickly, tangled branches would be difficult for a monkey to climb. Fossil evidence indicates that ancestral araucaria forests resembling the present day monkey puzzle date back to the age of dinosaurs. In fact, it has been suggested the tree’s armor of dagger-like leaves was designed to discourage enormous South American herbivorous dinosaurs, such as Argentinosaurus weighing and estimated 80 to 100 tons. Another ancient South American species called pino parana or parana pine (A. angustifolia) grows in southern Brazil and Argentina.
Any discussion of fossilized araucariads would be incomplete without mentioning a medieval gemstone called jet. Jet is a semi-precious gem excavated in Europe and formed by metamorphosis and anaerobic fossilization of araucaria wood buried under sediments in ancient seas. Ancestral forests that metamorphosed into jet date back to the Jurassic period, about 160 million years ago. They were similar to present day forests of monkey puzzle trees (Araucaria araucana) that grow in South America. Chemically, jet is hard, carbonized form of bituminous coal with a density similar to anthracite coal. Anthracite can be readily identified by its metallic luster. Jet takes a high polish and has been used for shiny black jewelry for thousands of years. It has a specific gravity of 1.3, almost as hard as the ironwood called lignum vitae (Guaiacum officinale). Jet became very popular during the mid 19th century England during the reign of Queen Victoria, and was often worn to ward off evil spirits and during times of mourning. In the first century AD, the Roman naturalist and writer Pliny described the magical and medicinal attributes of this beautiful mineral. The well-known analogy of ‘jet’ and ‘black’ was coined by William Shakespeare in his ‘black as jet’ from Henry VI part 2. One of the most famous areas for mining of Victorian jet is Whitby on the rugged Northeast coast of England. Although they are similar in hardness, anthracite has a metallic luster and jet is dull black. Jet takes a high polish and has been used in various carved jewelry, such as cameos and intaglios. The Victoria jet broach (circa 1890) was a popular item of jewelry during the 19th century.
Rare Diamond Goes Bright Pink In UV Light
(via Gemmology Queensland, Vol.5, No.7, July 2004/annanova.com 16/1/04)
A potentially unique diamond, which goes vivid pink when exposed to ultraviolet light, has been found in South Africa. The 13.7 carat diamond, being called the Tirisano Easter Diamond, was recovered from the Tirisano Diamond Mine in Ventersdorp diamond district of the Republic of South Africa.
Exposure to (presumably long wave) ultraviolet light causes the diamond to turn vibrant fluorescent pink. It’s not unusual for diamonds to change color in this way, but vivid pink is one of the rarest colors and the stone retains this hue for a period of time after UV exposure. Experts who have examined it so far consider it to be unique but the exact rarity of the stone will have to be established by a laboratory.
It is the property of mining companies Etruscan and Mountain Lake who plan to sell it by auction to a private collector. Les Meyer, a director of National Diamond Marketing, said, “I have had cause to view several million of stones but I have never come across a diamond of this nature, which leads me to believe that it is incredibly rare. It’s an exceptional piece due to the vibrant pink fluorescence and it has caused excitement amongst all who have examined it at National Diamond Marketing. Nobody can quite believe the color transition.”
A potentially unique diamond, which goes vivid pink when exposed to ultraviolet light, has been found in South Africa. The 13.7 carat diamond, being called the Tirisano Easter Diamond, was recovered from the Tirisano Diamond Mine in Ventersdorp diamond district of the Republic of South Africa.
Exposure to (presumably long wave) ultraviolet light causes the diamond to turn vibrant fluorescent pink. It’s not unusual for diamonds to change color in this way, but vivid pink is one of the rarest colors and the stone retains this hue for a period of time after UV exposure. Experts who have examined it so far consider it to be unique but the exact rarity of the stone will have to be established by a laboratory.
It is the property of mining companies Etruscan and Mountain Lake who plan to sell it by auction to a private collector. Les Meyer, a director of National Diamond Marketing, said, “I have had cause to view several million of stones but I have never come across a diamond of this nature, which leads me to believe that it is incredibly rare. It’s an exceptional piece due to the vibrant pink fluorescence and it has caused excitement amongst all who have examined it at National Diamond Marketing. Nobody can quite believe the color transition.”
Thursday, April 12, 2007
Crystal-pulled Synthetic Chrysoberyl
(via Gemmology Queensland, Vol.1, No.2, February 2000)
According to Dr Hisashi Machida, of Japan’s Kyocera Corporation, Inamori currently produces twelve (12) synthetics for gem purposes. These man-made materials include flux-grown emerald, flocculated silica based plastic impregnated white and black opal, and synthetic alexandrite, cat’s eye alexandrite, blue sapphire, ruby, star ruby, pink sapphire, yellow sapphire, padparadscha sapphire, and green chrysoberyl which Machida claims are synthesized by a combination of a flux process and pulling.
Japan’s Kyocera Corporation has been producing gem quality Czochralski grown (crystal pulled) synthetic chrysoberyl for many years. While yellow (Fe³+ bearing), colorless, and Cr³+ containing alexandrite chrysoberyls have been available for some years, green and pink chrysoberyl have only recently been added to the product list.
The light green colored synthetic chrysoberyl is virtually inclusion-free, and is colored by V³+ of similar concentration to that found in Tunduru chrysoberyl of comparable color. Detectable quantities of Fe, Ga, and Sn were not found in the Inamori crystal-pulled synthetic chrysoberyl.
A bluish green synthetic chrysoberyl of possible Russian origin, was colored by five times the V³+ found in equivalently colored natural chrysoberyl, about 0.2 wt% Cr2O3. Like the Inamori synthetic, this green synthetic chrysoberyl had no detectable Fe, Ga, Sn.
An experimental pink synthetic chrysoberyl was colored by Ti³+ (the same chromophore that is found in hydrothermally grown pink synthetic beryl. This synthetic also was virtually inclusion free.
According to Dr Hisashi Machida, of Japan’s Kyocera Corporation, Inamori currently produces twelve (12) synthetics for gem purposes. These man-made materials include flux-grown emerald, flocculated silica based plastic impregnated white and black opal, and synthetic alexandrite, cat’s eye alexandrite, blue sapphire, ruby, star ruby, pink sapphire, yellow sapphire, padparadscha sapphire, and green chrysoberyl which Machida claims are synthesized by a combination of a flux process and pulling.
Japan’s Kyocera Corporation has been producing gem quality Czochralski grown (crystal pulled) synthetic chrysoberyl for many years. While yellow (Fe³+ bearing), colorless, and Cr³+ containing alexandrite chrysoberyls have been available for some years, green and pink chrysoberyl have only recently been added to the product list.
The light green colored synthetic chrysoberyl is virtually inclusion-free, and is colored by V³+ of similar concentration to that found in Tunduru chrysoberyl of comparable color. Detectable quantities of Fe, Ga, and Sn were not found in the Inamori crystal-pulled synthetic chrysoberyl.
A bluish green synthetic chrysoberyl of possible Russian origin, was colored by five times the V³+ found in equivalently colored natural chrysoberyl, about 0.2 wt% Cr2O3. Like the Inamori synthetic, this green synthetic chrysoberyl had no detectable Fe, Ga, Sn.
An experimental pink synthetic chrysoberyl was colored by Ti³+ (the same chromophore that is found in hydrothermally grown pink synthetic beryl. This synthetic also was virtually inclusion free.
Wednesday, April 11, 2007
Identifying Synthetic Moissanite
(via Gems & Jewellery News, December 1998) Jamie Nelson writes:
If a large batch of unmounted diamonds of a range of sizes requires to be checked to determine if the batch has been salted with synthetic moissanites, then there is an easy alternative method to the methylene iodide sink or float separations.
Place the stones, table down, on the bottom of a shallow, flat bottomed, clear glass dish and cover all the stones completely with tap water. The much higher optical dispersion of moissanite (0.104 or almost x 2½ that of diamond) will reveal itself as bright spectral colored flashes, while diamonds (dispersion 0.044) will display less brightly colored sparkles. The method will still work with open-backed bracelets, necklaces and other items provided that all the stones lie table down (i.e. culet uppermost).
This being so, in the case of a finger ring mounted moissanite, the only piece of equipment needed to ensure a confident distinction is a battery-operated hand-held polariscope. The ring is placed between the polars so that the place of the stone’s table lies parallel to the optic axis of the polariscope, i.e. the long torch battery stem. The polariscope is then rotated in the axis of the torch barrel while keeping the ring stationary.
If the stone is moissanite, the usual winking of the stone’s image will be seen. If it is diamond, little or no change in the scattered light intensity will be observed. If the colorless stone happens to be another uniaxial or biaxial material, such as zircon, rutile, lithium niobate, corundum, scheelite, zincite, topaz or enstatite, then of course winking effects also will be seen. But all will be unable to pass a scratch-hardness test using the sharp edge of a carborundum (alpha silicon carbide) monocrystal applied cautiously to the girdle. However, our concern here is only to disclose the presence of moissanite and not to identify a nondiamond stone.
If a large batch of unmounted diamonds of a range of sizes requires to be checked to determine if the batch has been salted with synthetic moissanites, then there is an easy alternative method to the methylene iodide sink or float separations.
Place the stones, table down, on the bottom of a shallow, flat bottomed, clear glass dish and cover all the stones completely with tap water. The much higher optical dispersion of moissanite (0.104 or almost x 2½ that of diamond) will reveal itself as bright spectral colored flashes, while diamonds (dispersion 0.044) will display less brightly colored sparkles. The method will still work with open-backed bracelets, necklaces and other items provided that all the stones lie table down (i.e. culet uppermost).
This being so, in the case of a finger ring mounted moissanite, the only piece of equipment needed to ensure a confident distinction is a battery-operated hand-held polariscope. The ring is placed between the polars so that the place of the stone’s table lies parallel to the optic axis of the polariscope, i.e. the long torch battery stem. The polariscope is then rotated in the axis of the torch barrel while keeping the ring stationary.
If the stone is moissanite, the usual winking of the stone’s image will be seen. If it is diamond, little or no change in the scattered light intensity will be observed. If the colorless stone happens to be another uniaxial or biaxial material, such as zircon, rutile, lithium niobate, corundum, scheelite, zincite, topaz or enstatite, then of course winking effects also will be seen. But all will be unable to pass a scratch-hardness test using the sharp edge of a carborundum (alpha silicon carbide) monocrystal applied cautiously to the girdle. However, our concern here is only to disclose the presence of moissanite and not to identify a nondiamond stone.
Synthetic Aquamarine
(via Gemmology Queensland, Vol.1, No.2, February 2000)
Tairus first produced light to dark greenish blue synthetic aquamarine in Russia in the mid-1990s. It is synthesized hydrothermally, and owes its greenish color to small amounts of Fe²+ and a Fe²+ - Fe³+ charge transfer mechanism. It is grown as flat tabular crystals on seed plates oriented at an angle to the c-axis.
Hyrothermally grown synthetic aquamarine has the following gemological properties:
Color: Light to dark greenish blue
Specific gravity: 2.65 – 2.70
Refractive index: 1.587/1.580 – 1.571/1.577
Birefringence: 0.004/0.008
Pleochroism: Weak to strong blue/colorless
Fluorescence (UV): Inert
VIS absorption spectrum: Bands at 800nm (Fe²+ ), 375nm ( Fe³+ ), shoulder at 650nm (Fe²+ - Fe³+ charge transfer, line at 400nm (Ni³+)
It can be discriminated from natural aquamarine by its:
- Chevron-like growth banding that parallels the seed plate. This growth banding which is made up of pyramidal sub-cellular growth subunits is typical of hydrothermal growth occurring of seed plates oriented at an angle to its c-axis.
- Occasional presence of flake-like aggregates of Ni-pyrrhotite and Ni-pyrite.
Chemical analysis will reveal Ni³+ as a contaminant from the walls of the autoclave in which the synthetic aquamarine was grown.
Tairus first produced light to dark greenish blue synthetic aquamarine in Russia in the mid-1990s. It is synthesized hydrothermally, and owes its greenish color to small amounts of Fe²+ and a Fe²+ - Fe³+ charge transfer mechanism. It is grown as flat tabular crystals on seed plates oriented at an angle to the c-axis.
Hyrothermally grown synthetic aquamarine has the following gemological properties:
Color: Light to dark greenish blue
Specific gravity: 2.65 – 2.70
Refractive index: 1.587/1.580 – 1.571/1.577
Birefringence: 0.004/0.008
Pleochroism: Weak to strong blue/colorless
Fluorescence (UV): Inert
VIS absorption spectrum: Bands at 800nm (Fe²+ ), 375nm ( Fe³+ ), shoulder at 650nm (Fe²+ - Fe³+ charge transfer, line at 400nm (Ni³+)
It can be discriminated from natural aquamarine by its:
- Chevron-like growth banding that parallels the seed plate. This growth banding which is made up of pyramidal sub-cellular growth subunits is typical of hydrothermal growth occurring of seed plates oriented at an angle to its c-axis.
- Occasional presence of flake-like aggregates of Ni-pyrrhotite and Ni-pyrite.
Chemical analysis will reveal Ni³+ as a contaminant from the walls of the autoclave in which the synthetic aquamarine was grown.
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