(via ICA )
A beautiful sapphire blue colored stone, benitoite is a rare mineral and occurs in gem quality crystals only in the Diablo Range of California. Benitoite is named after the country in which it occurs—San Benito County. Having hardness of only 6½ on the Moh’s scale, benitoite is one of the rarest of all mineral that are suitable for jewelry.
Sapphire-blue benitoite is found in association with another rare titanium mineral—neptunite—in a matrix of white natrolite. Stones over 2 carats were very rare until when a deposit with larger stones….some weighing up to 6 carats….was found at the Benitoite Gem Mine in California. A pink benitoite has been reported, but it is extremely rare. Colorless crystals of benitoite are not uncommon but are not considered worth cutting. Benitoite also has been found as tiny grains in rock in a few other Californian localities, as well as in Belgium, Japan, Korea, and Texas. However, these deposits are of little importance to the gem trade.
There are several versions as to who actually discovered the stone; but one of the most likely accounts is that the in late 1906 a prospector by the name of James Crouch was searching for mercury and copper minerals in the area of the San Benito river in California. He discovered some blue crystals in a vein of white natrolite, and it was at first believed that they were sapphires. However, because of the strong colorless to blue dichroism revealed by the stones on subsequent testing by a jeweler, the precise identity of the stone was subsequently questioned. Crystals from this new find were sent to Dr George Louderback, Professor of Geology at the University of California at Berkeley. He identified these as a new mineral, and named it benitoite after its country of origin.
In October 1985, the Governor of California named benitoite California’s official State Gemstone.
Interestingly, it has been claimed that a large benitoite weighing over 6 carats was presented to Benito Mussolini in 1938 by the then Italian Ambassador to the United States. This led some, who were not familiar with the stone’s origin, to assume that benitoite was named after Benito Mussolini…because of the similarity with his first name.
Benitoite is a very beautiful gemstone, although it is not very well known compared to other colored gemstones. It has high refractive indices (1.757 – 1804) and a high dispersion (0.046 vs diamond’s 0.044). Thus the ‘fire’ of benitoite approximates that found in diamond; but the visual effect is masked by the dark blue body color of the stone. Interestingly, blue benitoite fluoresces and identifying strong bluish white when exposed to short wave ultraviolet wavelengths.
Gradually this lovely sapphire blue colored gemstone is beginning to receive the recognition it deserves, and it can now be found more frequently in fine jewelry…particularly in the USA.
Tuesday, March 27, 2007
The Life Cycle Of The Silver-lipped Pearl Oyster
(via Wahroongai News, Volume 33, Number 8, August 1999) Joseph Taylor (Project Manager, Atlas Pacific Ltd) writes:
The basis of the lucrative South-sea pearl industry, the silver or gold-lipped pearl oyster, Pinctada maxima, begins life with the odds well-stacked against its survival. As the oyster matures it generally begins its reproductive life as a male and may change sex to female later in life. The switch from male to female; and even back again, is triggered by environmental conditions. Excellent conditions in terms of food availability and water quality will favor development of females, while adverse conditions tend to favor males. In the wild the sex ratio of male to female is roughly equal in oysters larger than 15cm (greater than two years of age); however, on the farm there considerably more males than males—probably as a result of regular disturbance during cleaning and other farm activities.
In southern Indonesia and Australia (e.g. Kupang and Broome) the breeding season commences in September and continues through to late April or early May. The pearl breeding period is October to February. At Alyui Bay, Waigeo, the season is extended and we have been able to induce spawning (the release of eggs and sperm) in mid-June, and spawning has been observed into July.
Pearl oysters spawn as result of external stimuli such as rising water temperature or changes in salinity. In the hatchery spawning may be induced by increasing the water temperature in the holding tanks. Generally, males spawn before females. The release of sperm into the water stimulates spawning in ‘ripe’ females. Unfertilized eggs or ova are released in enormous numbers, a single female may release up to 50 million eggs. The eggs are initially pear-shaped and become spherical following fertilization. Fertilization in the wild is haphazard and will only occur where sperm and egg are united. In the vast bays and oceans that silver-lipped pearl oysters populate, the chances of successful fertilization are small. In the hatchery fertilization can be controlled due to small water volume and the close proximity of spawning males and females.
The division of cells after fertilization is rapid; and within 24 hours the newly developed larvae have a functional stomach and are able to swim. At this early stage they are called ‘D’ or straight hinge larvae. A week later, the larvae begin to change shape and become more rounded. They are now at the ‘umbo’ stage of life. At this time they are only 0.1mm in size, but appear very much like a cockle or pipi when viewed under a microscope. At between 16 and 20 days of age they will develop two red pigment spots called ‘eye spots’. The ‘eye spots’ are light sensitive. Within a few days the larvae will begin to develop a foot which is used to crawl snail-like on surfaces in order to search out appropriate place to settle. At this stage the larvae are called ‘pediveligers’ and are about 0.2 – 0.3 mm size. In the hatchery specially prepared rope panels, or collectors, are placed in the culture tanks to ‘catch’ settling larvae.
The first stage of settlement occurs when the ‘pediveliger’ secrets hair-like fibres (the byssus) from its fool. The byssal fibres adhere to the surfaces of collectors or other objects in the water. Once firmly attached, the ‘pediveliger’ will begin to metamorphose. This is a traumatic time and many of these larvae will not survive. During the three or four days following settlement larvae lose the ability to swim, and many of the organs that have served them during the early part of their lives are resorbed…….and new organs, such as gills, rapidly develop. The larval shell takes on a new shape and growth is very rapid. With the development of its new shell, the ‘oyster’ is now called ‘plantigrade’, and within a few days of settlement is already nearing a millimeter in size. The ‘plantigrade’ stage only lasts a few days before the small oyster becomes a ‘spat’. The ‘spat’ look much like the adult oyster but come in a multitude of colors that include yellow, brown, black, green and white. A prominent feature of young spat is ‘finger-like’ growth processes that they have along the edge of their shells. Over the next twelve months growth of spat is rapid and most oysters will have reached 10cm sizes during their first year of life.
Between 18 months and two years the silver or gold-lipped pearl oyster reaches maturity… and the cycle of reproduction and growth begin once more.
The basis of the lucrative South-sea pearl industry, the silver or gold-lipped pearl oyster, Pinctada maxima, begins life with the odds well-stacked against its survival. As the oyster matures it generally begins its reproductive life as a male and may change sex to female later in life. The switch from male to female; and even back again, is triggered by environmental conditions. Excellent conditions in terms of food availability and water quality will favor development of females, while adverse conditions tend to favor males. In the wild the sex ratio of male to female is roughly equal in oysters larger than 15cm (greater than two years of age); however, on the farm there considerably more males than males—probably as a result of regular disturbance during cleaning and other farm activities.
In southern Indonesia and Australia (e.g. Kupang and Broome) the breeding season commences in September and continues through to late April or early May. The pearl breeding period is October to February. At Alyui Bay, Waigeo, the season is extended and we have been able to induce spawning (the release of eggs and sperm) in mid-June, and spawning has been observed into July.
Pearl oysters spawn as result of external stimuli such as rising water temperature or changes in salinity. In the hatchery spawning may be induced by increasing the water temperature in the holding tanks. Generally, males spawn before females. The release of sperm into the water stimulates spawning in ‘ripe’ females. Unfertilized eggs or ova are released in enormous numbers, a single female may release up to 50 million eggs. The eggs are initially pear-shaped and become spherical following fertilization. Fertilization in the wild is haphazard and will only occur where sperm and egg are united. In the vast bays and oceans that silver-lipped pearl oysters populate, the chances of successful fertilization are small. In the hatchery fertilization can be controlled due to small water volume and the close proximity of spawning males and females.
The division of cells after fertilization is rapid; and within 24 hours the newly developed larvae have a functional stomach and are able to swim. At this early stage they are called ‘D’ or straight hinge larvae. A week later, the larvae begin to change shape and become more rounded. They are now at the ‘umbo’ stage of life. At this time they are only 0.1mm in size, but appear very much like a cockle or pipi when viewed under a microscope. At between 16 and 20 days of age they will develop two red pigment spots called ‘eye spots’. The ‘eye spots’ are light sensitive. Within a few days the larvae will begin to develop a foot which is used to crawl snail-like on surfaces in order to search out appropriate place to settle. At this stage the larvae are called ‘pediveligers’ and are about 0.2 – 0.3 mm size. In the hatchery specially prepared rope panels, or collectors, are placed in the culture tanks to ‘catch’ settling larvae.
The first stage of settlement occurs when the ‘pediveliger’ secrets hair-like fibres (the byssus) from its fool. The byssal fibres adhere to the surfaces of collectors or other objects in the water. Once firmly attached, the ‘pediveliger’ will begin to metamorphose. This is a traumatic time and many of these larvae will not survive. During the three or four days following settlement larvae lose the ability to swim, and many of the organs that have served them during the early part of their lives are resorbed…….and new organs, such as gills, rapidly develop. The larval shell takes on a new shape and growth is very rapid. With the development of its new shell, the ‘oyster’ is now called ‘plantigrade’, and within a few days of settlement is already nearing a millimeter in size. The ‘plantigrade’ stage only lasts a few days before the small oyster becomes a ‘spat’. The ‘spat’ look much like the adult oyster but come in a multitude of colors that include yellow, brown, black, green and white. A prominent feature of young spat is ‘finger-like’ growth processes that they have along the edge of their shells. Over the next twelve months growth of spat is rapid and most oysters will have reached 10cm sizes during their first year of life.
Between 18 months and two years the silver or gold-lipped pearl oyster reaches maturity… and the cycle of reproduction and growth begin once more.
Greek And Roman Jewellery
By R A Higgins
Metheun and Co Ltd
1961
Metheun and Co writes:
The subject of this book is jewellery from Classical lands from the Early Bronze Age (about 2500 B.C) to the Late Roman period (about A.D 400). It thus covers some 3000 years of almost continuous development.
A full account of the technical methods of making jewellery is followed by a description, period by period, of the jewellery itself. Some periods, such as the Etruscan, have been the subject of detailed studies, but others, such as the Minoan and Mycenaean, have been almost completely neglected by students of ancient jewellery. The author, who is an Assistant Keeper at the British Museum, is particularly fortunate to have at his disposal what is perhaps the finest general collection of ancient jewellery in the world. He has experience of excavation, and has worked on material at Mycenae and Knossos.
The narrative is supplemented by very full site-lists and bibliographical references, which serve as a foundation for the arguments brought forward in the text, and as a guide to further reading. There are 68 plates, four in color, and a number of line drawings.
It is hoped that this book will serve not only as an introduction to a fascinating subject, but also as a work of reference for museums, dealers, archaeologists and collectors.
Metheun and Co Ltd
1961
Metheun and Co writes:
The subject of this book is jewellery from Classical lands from the Early Bronze Age (about 2500 B.C) to the Late Roman period (about A.D 400). It thus covers some 3000 years of almost continuous development.
A full account of the technical methods of making jewellery is followed by a description, period by period, of the jewellery itself. Some periods, such as the Etruscan, have been the subject of detailed studies, but others, such as the Minoan and Mycenaean, have been almost completely neglected by students of ancient jewellery. The author, who is an Assistant Keeper at the British Museum, is particularly fortunate to have at his disposal what is perhaps the finest general collection of ancient jewellery in the world. He has experience of excavation, and has worked on material at Mycenae and Knossos.
The narrative is supplemented by very full site-lists and bibliographical references, which serve as a foundation for the arguments brought forward in the text, and as a guide to further reading. There are 68 plates, four in color, and a number of line drawings.
It is hoped that this book will serve not only as an introduction to a fascinating subject, but also as a work of reference for museums, dealers, archaeologists and collectors.
Monday, March 26, 2007
Tourmaline - Spinel Doublets
(via ICA Early Warning Flash, No. 36, April 2, 1990) GII writes:
Subject: Beads of Tourmaline-Spinel Doublets in a string of natural rubies.
Observations: The string consisted of 52 beads of red color. Each bead (average weight 20 carats) was individually tested for its gemological properties. 50 pieces were identified as Natural Rubies having inclusions of rutile and some crystal inclusions. All beads were transparent red colored and irregular in shape. All beads were showing dichroism in some position or the other.
Microscopic examination of the beads revealed that two of the beads were actually doublets. One portion of these two beads had typical inclusions of spinel (octahedral crystals and thin liquid films) and the other portion showed characteristic inclusions of tourmaline (thread-like cavities and trachites). On further examination the line of demarcation could also be noticed. Refractive indices (spot method) clearly showed that the beads were doublets of red tourmaline and red spinel; R.I 1.62 and 1.719 for tourmaline and spinel respectively.
Warning: The red colored doublets are beads of irregular shape and can be easily mistaken for rubies in the necklace. It is not sufficient to test only a few pieces in the necklace. The refractive indices for the beads should be obtained from different directions. It is also imperative to check the inclusions for all the beads in a necklace.
Subject: Beads of Tourmaline-Spinel Doublets in a string of natural rubies.
Observations: The string consisted of 52 beads of red color. Each bead (average weight 20 carats) was individually tested for its gemological properties. 50 pieces were identified as Natural Rubies having inclusions of rutile and some crystal inclusions. All beads were transparent red colored and irregular in shape. All beads were showing dichroism in some position or the other.
Microscopic examination of the beads revealed that two of the beads were actually doublets. One portion of these two beads had typical inclusions of spinel (octahedral crystals and thin liquid films) and the other portion showed characteristic inclusions of tourmaline (thread-like cavities and trachites). On further examination the line of demarcation could also be noticed. Refractive indices (spot method) clearly showed that the beads were doublets of red tourmaline and red spinel; R.I 1.62 and 1.719 for tourmaline and spinel respectively.
Warning: The red colored doublets are beads of irregular shape and can be easily mistaken for rubies in the necklace. It is not sufficient to test only a few pieces in the necklace. The refractive indices for the beads should be obtained from different directions. It is also imperative to check the inclusions for all the beads in a necklace.
The Bridges Of Madison County
Memorable quote (s) from the movie:
Francesca (Meryl Streep): Robert, please. You don't understand; no-one does. When a woman makes the choice to marry, to have children; in one way her life begins but in another way it stops. You build a life of details. You become a mother, a wife and you stop and stay steady so that your children can move. And when they leave they take your life of details with them. And then you're expected move again only you don't remember what moves you because no-one has asked in so long. Not even yourself. You never in your life think that love like this can happen to you.
Robert Kincaid (Clint Eastwood): But now that you have it...
Francesca (Meryl Streep): I want to keep it forever. I want to love you the way I do now the rest of my life. Don't you understand... we'll lose it if we leave; I can't make an entire life disappear to start a new one. All I can do is try to hold onto to both. Help me. Help me not lose loving you.
Francesca (Meryl Streep): Robert, please. You don't understand; no-one does. When a woman makes the choice to marry, to have children; in one way her life begins but in another way it stops. You build a life of details. You become a mother, a wife and you stop and stay steady so that your children can move. And when they leave they take your life of details with them. And then you're expected move again only you don't remember what moves you because no-one has asked in so long. Not even yourself. You never in your life think that love like this can happen to you.
Robert Kincaid (Clint Eastwood): But now that you have it...
Francesca (Meryl Streep): I want to keep it forever. I want to love you the way I do now the rest of my life. Don't you understand... we'll lose it if we leave; I can't make an entire life disappear to start a new one. All I can do is try to hold onto to both. Help me. Help me not lose loving you.
How Crystals Grow
(via Wahroongai News, Volume 32, Number 8, August 1998) I Sunagawa writes:
Mechanisms of growth
Single crystal synthetics, for jewelry purposes, are grown by two mechanisms: either growth from the melt, or growth from solution. Natural crystal growth is essentially solution growth—either from high temperature inorganic solutions (magmatic crystallization), or from aequeous solutions (supergene, hydrothermal, pneumatolytic, and metamorphic crystallization).
Melt growth
Single crystal growth from the pure melt phase—using Verneuil, float zone, or skull melt, etc technologies—is quite different from the mechanism of crystal growth that occurs in nature. For example, the curved growth (color zoning) of Verneuil synthetics is due to the fact that the solid-liquid interface in melt growth is atomistically rough (thus providing many sites for attachment of the melt to the interface of the growing crystal), and is curved in concordance with the isotherm at this growth interface. In addition, the spacial distribution of dislocations in melt grown crystals also differs from that of natural crystals—which grow from a solution phase.
Solution growth
Under solution growth conditions growth temperatures are lower, and mass transfer processes and solute-solvent interactions play a large part in the crystallization process. As a consequence, the solid-liquid interfaces of solution grown single crystals are atomistically smoother than those of melt growth crystals. This causes crystals grown from solution to have a tendency to develop polyganol crystal shapes that are bounded by flat low index faces. Indeed, this mechanism of growth is reflected in the habits, faces, surface microtopographies (growth spirals, etc), inhomogeneties, and imperfections in the crystals—and their resulting cut stones. Although natural and synthetic crystals each are grown from solutions phases; the crystals have distinct and identifiable growth features that positively identify their mode of formation. Also, synthetic gemstones grown from solutions phases—such as high temperature flux growth, hydrothermal and aequeous growth—do display a range of growth features that are quite different from those of melt growth synthetics.
In solution growth, the solute-solvent complex is transported from the bulk solution to the solid-liquid (growth) interface by diffusion and/or convection. Here the solute is released from its solvent through a desolvation process. The major driving force for crystal growth is a high concentration diffusion boundary layer that develops at the growth interface of the crystal. The rate at which the solute is incorporated into the crystal structure is controlled by the roughness of this solid-liquid interface.
For example, when the interface is atomistically rough, the universal presence of kink sites allows ready incorporation of the solute by adhesive growth, and so allow the interface to grow homogeneously and at a growth rate normal to the interface that is linearly related to the driving force. In contrast, when the interface is atomistically smooth (consisting of flat terraces, steps, and kinks in the step) the solute has difficulty finding suitable sites (e.g kink in a step, outcrops of screw dislocations) that will allow it to be incorporated into the growing crystal. As a result, growth will proceed through lateral, two dimensional spreading of growth layers parallel to the interface. Growth on smooth interfaces is slowest, so the face will develop as the most developed crystal face.
Summary
1. Crystal growth (and dissolution) rates are anisotropic and are controlled by the degree of roughness of the growth interface, e.g. rough interfaces grow fastest, while smooth interfaces grow slowly but are well developed.
2. Growth rates (habits) are modified by growth parameters such as solvent chemistry, impurity content, growth temperature and pressure, supersaturation, etc.
3. Growth sectors form in single crystals due to anisotropic growth rates associated with impurity partitioning at growth interfaces.
4. Growth rates may fluctuate within growth sectors due to fluctuations in overall growth parameters, or imbalance between diffusion and incorporation rates. This leads to variations in the concentration and distribution of point defects and impurity elements responsible for growth or color banding in growth sectors. Growth banding may be straight and parallel, or curved and hummocky—depending on the roughness of the growth surface interface. For example, natural diamonds {111} growth is straight and parallel, while its {100} growth is hummocky.
5. The partition of elements in the growth solution depends both on thermodynamics and growth kinetics. For example, Nitrogen is more concentrated in {111} sectors in diamond than {100} sectors.
6. Changed conditions during growth often lead to dissolution and regrowth, or transformation from one growth morphology to another.
7. Inclusions are trapped particularly when growth parameters are changed, on the surface of seeds, at growth sector boundaries, and at twin compositional planes. Growth controlling dislocations are often generated by these inclusions.
8. Following crystal growth, exsolution or plastic deformation induced phase changes will superimpose exsolution lamellae, mechanical twin lamellae, and dislocation tangles on pre-existing growth features.
Mechanisms of growth
Single crystal synthetics, for jewelry purposes, are grown by two mechanisms: either growth from the melt, or growth from solution. Natural crystal growth is essentially solution growth—either from high temperature inorganic solutions (magmatic crystallization), or from aequeous solutions (supergene, hydrothermal, pneumatolytic, and metamorphic crystallization).
Melt growth
Single crystal growth from the pure melt phase—using Verneuil, float zone, or skull melt, etc technologies—is quite different from the mechanism of crystal growth that occurs in nature. For example, the curved growth (color zoning) of Verneuil synthetics is due to the fact that the solid-liquid interface in melt growth is atomistically rough (thus providing many sites for attachment of the melt to the interface of the growing crystal), and is curved in concordance with the isotherm at this growth interface. In addition, the spacial distribution of dislocations in melt grown crystals also differs from that of natural crystals—which grow from a solution phase.
Solution growth
Under solution growth conditions growth temperatures are lower, and mass transfer processes and solute-solvent interactions play a large part in the crystallization process. As a consequence, the solid-liquid interfaces of solution grown single crystals are atomistically smoother than those of melt growth crystals. This causes crystals grown from solution to have a tendency to develop polyganol crystal shapes that are bounded by flat low index faces. Indeed, this mechanism of growth is reflected in the habits, faces, surface microtopographies (growth spirals, etc), inhomogeneties, and imperfections in the crystals—and their resulting cut stones. Although natural and synthetic crystals each are grown from solutions phases; the crystals have distinct and identifiable growth features that positively identify their mode of formation. Also, synthetic gemstones grown from solutions phases—such as high temperature flux growth, hydrothermal and aequeous growth—do display a range of growth features that are quite different from those of melt growth synthetics.
In solution growth, the solute-solvent complex is transported from the bulk solution to the solid-liquid (growth) interface by diffusion and/or convection. Here the solute is released from its solvent through a desolvation process. The major driving force for crystal growth is a high concentration diffusion boundary layer that develops at the growth interface of the crystal. The rate at which the solute is incorporated into the crystal structure is controlled by the roughness of this solid-liquid interface.
For example, when the interface is atomistically rough, the universal presence of kink sites allows ready incorporation of the solute by adhesive growth, and so allow the interface to grow homogeneously and at a growth rate normal to the interface that is linearly related to the driving force. In contrast, when the interface is atomistically smooth (consisting of flat terraces, steps, and kinks in the step) the solute has difficulty finding suitable sites (e.g kink in a step, outcrops of screw dislocations) that will allow it to be incorporated into the growing crystal. As a result, growth will proceed through lateral, two dimensional spreading of growth layers parallel to the interface. Growth on smooth interfaces is slowest, so the face will develop as the most developed crystal face.
Summary
1. Crystal growth (and dissolution) rates are anisotropic and are controlled by the degree of roughness of the growth interface, e.g. rough interfaces grow fastest, while smooth interfaces grow slowly but are well developed.
2. Growth rates (habits) are modified by growth parameters such as solvent chemistry, impurity content, growth temperature and pressure, supersaturation, etc.
3. Growth sectors form in single crystals due to anisotropic growth rates associated with impurity partitioning at growth interfaces.
4. Growth rates may fluctuate within growth sectors due to fluctuations in overall growth parameters, or imbalance between diffusion and incorporation rates. This leads to variations in the concentration and distribution of point defects and impurity elements responsible for growth or color banding in growth sectors. Growth banding may be straight and parallel, or curved and hummocky—depending on the roughness of the growth surface interface. For example, natural diamonds {111} growth is straight and parallel, while its {100} growth is hummocky.
5. The partition of elements in the growth solution depends both on thermodynamics and growth kinetics. For example, Nitrogen is more concentrated in {111} sectors in diamond than {100} sectors.
6. Changed conditions during growth often lead to dissolution and regrowth, or transformation from one growth morphology to another.
7. Inclusions are trapped particularly when growth parameters are changed, on the surface of seeds, at growth sector boundaries, and at twin compositional planes. Growth controlling dislocations are often generated by these inclusions.
8. Following crystal growth, exsolution or plastic deformation induced phase changes will superimpose exsolution lamellae, mechanical twin lamellae, and dislocation tangles on pre-existing growth features.
Chameleon Diamonds
(via Wahroongai News, Volume 32, Number 4, April 1998)
Chameleon diamonds are rare hydrogen-rich diamonds that change color when exposed to heat. The most famous named chameleon diamond is the 22.28 ct heat-shaped Green Chameleon diamond—a diamond that changes color from grayish green to bright yellow under one of two circumstances.
Heat the green (stable color) chameleon diamond in the flame of an alcohol lamp to a temperature of 200 – 300ºC and its color will convert to an unstable bright yellow. Overheating to ~ 500ºC. If the unstable yellow colored chameleon diamond is in the dark for 24 of more hours, within a few minutes of its removal form the warm darkness its color will revert from unstable bright yellow to stable green color which is caused by the absorption of UV wavelengths from visible light.
The cause of this chameleon effect is an extremely broad absorption extending from ~ 550nm into the infrared, leaving a green window in the visible. Green chameleon diamonds also display characteristic greenish yellow phosphorescence to LWUV, which may last for several minutes after irradiation ceases.
Over recent years at least two other chameleon-type diamonds have been discovered:
-The first group is some pink Argyle diamonds that briefly change to brownish pink when subjected to strong UV irradiation
-The second group is a single specimen that changes from faint pink to colorless after UV irradiation. Gentle heating returns the faint pink color to this diamond. When exposed to UV light this chameleon has a strong apricot pink fluorescence, but a protracted yellowish green phosphorescence to follow.
Chameleon diamonds are rare hydrogen-rich diamonds that change color when exposed to heat. The most famous named chameleon diamond is the 22.28 ct heat-shaped Green Chameleon diamond—a diamond that changes color from grayish green to bright yellow under one of two circumstances.
Heat the green (stable color) chameleon diamond in the flame of an alcohol lamp to a temperature of 200 – 300ºC and its color will convert to an unstable bright yellow. Overheating to ~ 500ºC. If the unstable yellow colored chameleon diamond is in the dark for 24 of more hours, within a few minutes of its removal form the warm darkness its color will revert from unstable bright yellow to stable green color which is caused by the absorption of UV wavelengths from visible light.
The cause of this chameleon effect is an extremely broad absorption extending from ~ 550nm into the infrared, leaving a green window in the visible. Green chameleon diamonds also display characteristic greenish yellow phosphorescence to LWUV, which may last for several minutes after irradiation ceases.
Over recent years at least two other chameleon-type diamonds have been discovered:
-The first group is some pink Argyle diamonds that briefly change to brownish pink when subjected to strong UV irradiation
-The second group is a single specimen that changes from faint pink to colorless after UV irradiation. Gentle heating returns the faint pink color to this diamond. When exposed to UV light this chameleon has a strong apricot pink fluorescence, but a protracted yellowish green phosphorescence to follow.
Riches Of The Earth
By Frank J Anderson
The Rutledge Press
1981 ISBN 0-8317-7739-7
The Rutledge Press writes:
Because of their beauty and usefulness, ornamental, precious, and semi-precious stones have always had a close relationship with human civilization, whether endowed with religious significance, used as building materials, or wrought into works of art.
Riches of the Earth presents a vivid survey of the unique histories of the major precious and semi-precious stones. Beginning with prehistoric man’s first tools and ending with laser beams and holographs, the chapters of Riches of the Earth deal with religion, magic, superstition; associations with famous people and places; legends, discoveries, forgeries, and thefts. Among the wealth of material are the colorful myths surrounding Chinese jade, the story of ornamental stones during the Middle Ages, the magnificence of the world’s most precious royal collections, the symbolism of stones, stories of beautiful treasures lost, and the real powers of stones used today—plus a chapter on the what, where, and how of collecting.
Forty eight pages of full color illustrations enhance this fascinating history of man’s ongoing enchantment with stones. Riches of the Earth is a delight for the connoisseur and a display of excellence to inspire every collector of rocks and minerals.
The Rutledge Press
1981 ISBN 0-8317-7739-7
The Rutledge Press writes:
Because of their beauty and usefulness, ornamental, precious, and semi-precious stones have always had a close relationship with human civilization, whether endowed with religious significance, used as building materials, or wrought into works of art.
Riches of the Earth presents a vivid survey of the unique histories of the major precious and semi-precious stones. Beginning with prehistoric man’s first tools and ending with laser beams and holographs, the chapters of Riches of the Earth deal with religion, magic, superstition; associations with famous people and places; legends, discoveries, forgeries, and thefts. Among the wealth of material are the colorful myths surrounding Chinese jade, the story of ornamental stones during the Middle Ages, the magnificence of the world’s most precious royal collections, the symbolism of stones, stories of beautiful treasures lost, and the real powers of stones used today—plus a chapter on the what, where, and how of collecting.
Forty eight pages of full color illustrations enhance this fascinating history of man’s ongoing enchantment with stones. Riches of the Earth is a delight for the connoisseur and a display of excellence to inspire every collector of rocks and minerals.
Sunday, March 25, 2007
My Fair Lady
Memorable quote (s) from the movie:
Mrs. Higgins (Gladys Cooper): However did you learn good manners with my son around?
Eliza Doolittle (Audrey Hepburn): It was very difficult. I should never have known how ladies and gentlemen really behaved, if it hadn't been for Colonel Pickering. He always showed what he thought and felt about me as if I were something better than a common flower girl. You see, Mrs. Higgins, apart from the things one can pick up, the difference between a lady and a flower girl is not how she behaves, but how she is treated. I shall always be a common flower girl to Professor Higgins, because he always treats me like a common flower girl, and always will. But I know that I shall always be a lady to Colonel Pickering, because he always treats me like a lady, and always will.
Mrs. Higgins (Gladys Cooper): However did you learn good manners with my son around?
Eliza Doolittle (Audrey Hepburn): It was very difficult. I should never have known how ladies and gentlemen really behaved, if it hadn't been for Colonel Pickering. He always showed what he thought and felt about me as if I were something better than a common flower girl. You see, Mrs. Higgins, apart from the things one can pick up, the difference between a lady and a flower girl is not how she behaves, but how she is treated. I shall always be a common flower girl to Professor Higgins, because he always treats me like a common flower girl, and always will. But I know that I shall always be a lady to Colonel Pickering, because he always treats me like a lady, and always will.
A Couple Of Unusual Diamonds
(via Wahroongai News, Volume 32, Number 4, April 1998)
The appearance in the marketplace of parcels of saturated greenish yellow to yellowish green to brownish fancy colored diamonds—with unusual characteristics—has led to suggestions that these colors could have been induced by a new hyperbaric heating treatment that consists of high temperature and pressure heat treatment (? in a Russian Bars apparatus) that reverses naturally occurring aggregation of nitrogen in the diamonds. Suggested source material for this treatment is low quality, mostly Argyle-type natural diamonds.
The treated diamond’s color has two components: a saturated yellow to brownish body color and a strong greenish luminescence to strong visible light emitted by distinctively visible brownish yellow growth lines in the diamond. This gives the green transmitter diamond’s body color a greenish overcast that is readily visible in daylight. When viewed in somewhat subdued lighting these strongly green fluorescent growth lines often contrast strongly against the brownish body color of the diamonds. When exposed to LWUV the growth lines fluoresce a strong green. Examination of the diamond under magnification reveals prominent graining and color zoning paralleling octahedral faces, pitted and corroded (? burnt) facet junctions, girdle, external surfaces of surface-reaching fractures, and heavily bearded girdles.
Examination with gemological hand-held spectroscope revealed pairs of absorption and bright emission lines at 513 and 518nm, absorption lines at 415 (N3 center) and 503nm (H3 center), and a broad absorption band between 465 and 494nm. A more detailed examination with a spectrophotometer confirmed the presence of these features and added a weak absorption peak at 637nm and a weak to strong peak at 985nm (in the invisible near-infrared)—which was assigned to the irradiation high temperature (>1400ºC) annealing induced H2 center.
It is concerning that none of these obviously treated greenish yellow to yellow green to brown diamonds displayed the 595nm, 741nm (GR1) or HIb and HIc absorptions that would be expected to be found in irradiated and heat treated yellow or green diamonds.
The appearance in the marketplace of parcels of saturated greenish yellow to yellowish green to brownish fancy colored diamonds—with unusual characteristics—has led to suggestions that these colors could have been induced by a new hyperbaric heating treatment that consists of high temperature and pressure heat treatment (? in a Russian Bars apparatus) that reverses naturally occurring aggregation of nitrogen in the diamonds. Suggested source material for this treatment is low quality, mostly Argyle-type natural diamonds.
The treated diamond’s color has two components: a saturated yellow to brownish body color and a strong greenish luminescence to strong visible light emitted by distinctively visible brownish yellow growth lines in the diamond. This gives the green transmitter diamond’s body color a greenish overcast that is readily visible in daylight. When viewed in somewhat subdued lighting these strongly green fluorescent growth lines often contrast strongly against the brownish body color of the diamonds. When exposed to LWUV the growth lines fluoresce a strong green. Examination of the diamond under magnification reveals prominent graining and color zoning paralleling octahedral faces, pitted and corroded (? burnt) facet junctions, girdle, external surfaces of surface-reaching fractures, and heavily bearded girdles.
Examination with gemological hand-held spectroscope revealed pairs of absorption and bright emission lines at 513 and 518nm, absorption lines at 415 (N3 center) and 503nm (H3 center), and a broad absorption band between 465 and 494nm. A more detailed examination with a spectrophotometer confirmed the presence of these features and added a weak absorption peak at 637nm and a weak to strong peak at 985nm (in the invisible near-infrared)—which was assigned to the irradiation high temperature (>1400ºC) annealing induced H2 center.
It is concerning that none of these obviously treated greenish yellow to yellow green to brown diamonds displayed the 595nm, 741nm (GR1) or HIb and HIc absorptions that would be expected to be found in irradiated and heat treated yellow or green diamonds.
Sphalerite
(via Wahroongai News, Volume 30, No 12, December, 1996) Grahame Brown writes:
Sphalerite, otherwise known as zinc blende (Zn, Fe, S), is a cubic mineral that commonly occurs as yellow, brown, orange, green, red, and colorless to gray isometric crystals and cleavage fragments. Due to sphalerite’s high refractive index (2.37-2.43), and a very high dispersion (0.156 or x4 diamond), this principal ore of zinc displays a vitreous to adamantine luster on polished surfaces. Its specific gravity varies from 3.9 to 4.1, depending principally on its iron content. Faceted gems, cut from sphalerite, display many diamond-like characteristics. Consequently, this mineral has been used to imitate diamond—in spite of its ready, perfect dodecahedral (6-directions) cleavage.
The source of some of the world’s finest specimen of this mineral have been the lead zinc deposits of the Picos de Europa Mountains in the Cantabria region of northern Spain. The mines of this area, and their minerals, were described and illustrated by de Baranda & Garcia in the May – June 1996 issue of the Mineralogical Record (pp 177-190).
The mines of this area, particularly the Aliva mines, have been sources of gem quality sphalerite from the 1860s until 1990 (when the last mine ceased operations and was permanently sealed). Aliva mine sphalerite, which occurs with smithsonite, hydrozincite, hemimorphite and other sulphides, such as galena, is found in a carbonate (calcite and dolomite) gangue that fills veins and pockets in carbonaceous limestones that form the mountain/s of the region.
Chemical analysis of this sphalerite have revealed that the causes of its attractive red, yellow and green colors are quite complex. While this sphalerite does contain variable amounts of iron, its various colors also contain variable amounts of other rare elements such as germanium, cadmium, and significant amounts of mercury. The interplay of these elemental impurities in creating various colors is interesting. For example, yellow and green varieties contain little germanium, while green varieties contain highest levels of iron, and red varieties contain highest levels of both cadmium and mercury. Obviously there is a need for additional research before precise cause of color of this sphalerite can be established.
Undoubtedly the best paper written on the very gemmy sphalerites from the Aliva mine is a 1992 paper titled Estudio de la esfalerita la mina de Aliva Santander (Espana) by Cristina Sapalski & Fernando Gomez that was published in the June issue of Boletin del Insituto Gemologico Espanol.
Sphalerite, otherwise known as zinc blende (Zn, Fe, S), is a cubic mineral that commonly occurs as yellow, brown, orange, green, red, and colorless to gray isometric crystals and cleavage fragments. Due to sphalerite’s high refractive index (2.37-2.43), and a very high dispersion (0.156 or x4 diamond), this principal ore of zinc displays a vitreous to adamantine luster on polished surfaces. Its specific gravity varies from 3.9 to 4.1, depending principally on its iron content. Faceted gems, cut from sphalerite, display many diamond-like characteristics. Consequently, this mineral has been used to imitate diamond—in spite of its ready, perfect dodecahedral (6-directions) cleavage.
The source of some of the world’s finest specimen of this mineral have been the lead zinc deposits of the Picos de Europa Mountains in the Cantabria region of northern Spain. The mines of this area, and their minerals, were described and illustrated by de Baranda & Garcia in the May – June 1996 issue of the Mineralogical Record (pp 177-190).
The mines of this area, particularly the Aliva mines, have been sources of gem quality sphalerite from the 1860s until 1990 (when the last mine ceased operations and was permanently sealed). Aliva mine sphalerite, which occurs with smithsonite, hydrozincite, hemimorphite and other sulphides, such as galena, is found in a carbonate (calcite and dolomite) gangue that fills veins and pockets in carbonaceous limestones that form the mountain/s of the region.
Chemical analysis of this sphalerite have revealed that the causes of its attractive red, yellow and green colors are quite complex. While this sphalerite does contain variable amounts of iron, its various colors also contain variable amounts of other rare elements such as germanium, cadmium, and significant amounts of mercury. The interplay of these elemental impurities in creating various colors is interesting. For example, yellow and green varieties contain little germanium, while green varieties contain highest levels of iron, and red varieties contain highest levels of both cadmium and mercury. Obviously there is a need for additional research before precise cause of color of this sphalerite can be established.
Undoubtedly the best paper written on the very gemmy sphalerites from the Aliva mine is a 1992 paper titled Estudio de la esfalerita la mina de Aliva Santander (Espana) by Cristina Sapalski & Fernando Gomez that was published in the June issue of Boletin del Insituto Gemologico Espanol.
From The World Of Gemstones
By Prof Dr Hermann Bank
Pinguin – Verlag
1973
Prof Dr Hermann Bank writes:
Gemstones—from antiquity this concept has conjured up the image of something beautiful, something precious, transcending everyday life. Gems are pre-eminently part of the festive occasions of life, of the (now rare) coronations of emperors and kings, of state receptions, evenings at the opera, soirees and family feasts. Set in the appropriate noble metals, they are favored gifts at engagements, weddings, births and similar occasions. Their manifold usage—dynastic, religious, mystic, therapeutic—as well as their employment for adornment and in the industry shows the enormous extent of The World of Gemstones. Apart from the uses of gems it embraces their origin, their recovery, their fashioning and setting, their imitation, testing and evaluation. The present book attempts to answer concisely and intelligibly the manifold questions From The World of Gemstones which have been put by interested laymen, students and budding gemologists during talks, visits to lapidary establishments and lectures. Numerous pictures are intended to complete the information about The World of Gemstones.
About the author
Prof Dr Hermann Bank was the first Chairman of the German Gemmological Society. He taught gemology at the universities of Heidelberg and Mainz, and is the owner of a gem cutting establishment at Idar Oberstein, Germany.
Pinguin – Verlag
1973
Prof Dr Hermann Bank writes:
Gemstones—from antiquity this concept has conjured up the image of something beautiful, something precious, transcending everyday life. Gems are pre-eminently part of the festive occasions of life, of the (now rare) coronations of emperors and kings, of state receptions, evenings at the opera, soirees and family feasts. Set in the appropriate noble metals, they are favored gifts at engagements, weddings, births and similar occasions. Their manifold usage—dynastic, religious, mystic, therapeutic—as well as their employment for adornment and in the industry shows the enormous extent of The World of Gemstones. Apart from the uses of gems it embraces their origin, their recovery, their fashioning and setting, their imitation, testing and evaluation. The present book attempts to answer concisely and intelligibly the manifold questions From The World of Gemstones which have been put by interested laymen, students and budding gemologists during talks, visits to lapidary establishments and lectures. Numerous pictures are intended to complete the information about The World of Gemstones.
About the author
Prof Dr Hermann Bank was the first Chairman of the German Gemmological Society. He taught gemology at the universities of Heidelberg and Mainz, and is the owner of a gem cutting establishment at Idar Oberstein, Germany.
Sideways
Memorable quote (s) from the movie:
Jack (Thomas Haden Church): I might be in love with another woman.
Miles Raymond (Paul Giamatti): In love? Really? 24 hours with some wine-pourer chick and you're fucking in love? Come on! And you're gonna give up everything?
Jack (Thomas Haden Church): Here's what I'm thinking: you and me, we move up here, we buy a vineyard. You design the wine; I'll handle the business side. You get inspired; maybe write another novel, one that can sell.
Miles Raymond (Paul Giamatti): Oh, my God. No, no.
Jack (Thomas Haden Church): As for me, if an audition comes up, LA's right there, man. It's two hours away, not even.........
Miles Raymond (Paul Giamatti): Jesus Christ, you're crazy. You're crazy. You've gone crazy.
Jack (Thomas Haden Church): All I know is that I'm an actor. All I have is my instinct. You're asking me to go against it.
Jack (Thomas Haden Church): I might be in love with another woman.
Miles Raymond (Paul Giamatti): In love? Really? 24 hours with some wine-pourer chick and you're fucking in love? Come on! And you're gonna give up everything?
Jack (Thomas Haden Church): Here's what I'm thinking: you and me, we move up here, we buy a vineyard. You design the wine; I'll handle the business side. You get inspired; maybe write another novel, one that can sell.
Miles Raymond (Paul Giamatti): Oh, my God. No, no.
Jack (Thomas Haden Church): As for me, if an audition comes up, LA's right there, man. It's two hours away, not even.........
Miles Raymond (Paul Giamatti): Jesus Christ, you're crazy. You're crazy. You've gone crazy.
Jack (Thomas Haden Church): All I know is that I'm an actor. All I have is my instinct. You're asking me to go against it.
Natural Colored Blue Quartz
(via Wahroongai News, Volume 30, No.7, July 1996) Grahame Brown writes:
For many years I have made the general statement in lectures on synthetics that ‘blue quartz is never difficult to identify, for blue quartz does not occur naturally’. It would seem that this statement could, and should, be challenged. The reason for this change of opinion is a small paper that was published in the March-April 1996 issue of The Mineralogical Record.
The paper, titled ‘Blue quartz from the Antequera-Olvera Ophite, Malaga, Spain’, describes the occurrence of attractive dipyramidal blue quartz owing its color to aerinite inclusions.
Apparently blue quartz was first reported from the Antequera region of Spain in 1910. This deposit was rediscovered near the Olvera-Pruna road in Cadiz province—a small province that lies just to the east of the British fortress of Gibraltar. Here a clay-lined fractures in an ophitic (rock with a texture dominated by lath-shaped plagioclase crystals completely included within pyroxene) augite diabase = dolerite (a dark colored intrusive rock, containing major labradorite and pyroxene, which characteristically has an ophitic texture) rock host well crystallized dipyramidal (consisting of equally developed positive and negative rhombohedron) blue quartz crystals of 5mm to 1.5cm size.
The blue quartz crystals are actually colorless quartz crystals that are included by fibrous aerinite. These crystals vary in color from deep blue to sky blue. For the interested reader, aerinite is a monoclinic mineral that commonly adopts a fibrous habit.
Other possible causes of blue quartz are……the inclusion of colorless quartz by:
- Submicroscopic inclusions of rutile, producing a blue color in the quartz by Tyndall scattering of white light, and
- Dumortierite, a bluish to purple orthorhombic mineral.
For many years I have made the general statement in lectures on synthetics that ‘blue quartz is never difficult to identify, for blue quartz does not occur naturally’. It would seem that this statement could, and should, be challenged. The reason for this change of opinion is a small paper that was published in the March-April 1996 issue of The Mineralogical Record.
The paper, titled ‘Blue quartz from the Antequera-Olvera Ophite, Malaga, Spain’, describes the occurrence of attractive dipyramidal blue quartz owing its color to aerinite inclusions.
Apparently blue quartz was first reported from the Antequera region of Spain in 1910. This deposit was rediscovered near the Olvera-Pruna road in Cadiz province—a small province that lies just to the east of the British fortress of Gibraltar. Here a clay-lined fractures in an ophitic (rock with a texture dominated by lath-shaped plagioclase crystals completely included within pyroxene) augite diabase = dolerite (a dark colored intrusive rock, containing major labradorite and pyroxene, which characteristically has an ophitic texture) rock host well crystallized dipyramidal (consisting of equally developed positive and negative rhombohedron) blue quartz crystals of 5mm to 1.5cm size.
The blue quartz crystals are actually colorless quartz crystals that are included by fibrous aerinite. These crystals vary in color from deep blue to sky blue. For the interested reader, aerinite is a monoclinic mineral that commonly adopts a fibrous habit.
Other possible causes of blue quartz are……the inclusion of colorless quartz by:
- Submicroscopic inclusions of rutile, producing a blue color in the quartz by Tyndall scattering of white light, and
- Dumortierite, a bluish to purple orthorhombic mineral.
It’s All In The State Of Mind
Author Unknown.
If you think you are beaten, you are
If you think you dare not, you don’t
If you think you’d like to win, but can’t
It’s almost a ‘cinch’ you won’t
If you think you’ll lose, you’ve lost
For out in the world you’ll find
Success begins with a fellow’s will
It’s all in the state of mind
For many a race is lost
Ere even a race is run
And many a coward fails
Ere ever his work’s begun
Think big and your deeds will grow
Think small and you fall behind
Think that you can, and you will
It’s all in the state of the mind
If you think you’re outclassed, you are
You’ve got to think hard to rise
You’ve got to be sure of yourself before
You can ever win a prize
Life’s battle doesn’t always go
To the strongest or fastest man
But sooner or later the man who wins
Is the man who thinks he can
If you think you are beaten, you are
If you think you dare not, you don’t
If you think you’d like to win, but can’t
It’s almost a ‘cinch’ you won’t
If you think you’ll lose, you’ve lost
For out in the world you’ll find
Success begins with a fellow’s will
It’s all in the state of mind
For many a race is lost
Ere even a race is run
And many a coward fails
Ere ever his work’s begun
Think big and your deeds will grow
Think small and you fall behind
Think that you can, and you will
It’s all in the state of the mind
If you think you’re outclassed, you are
You’ve got to think hard to rise
You’ve got to be sure of yourself before
You can ever win a prize
Life’s battle doesn’t always go
To the strongest or fastest man
But sooner or later the man who wins
Is the man who thinks he can
Geological Laboratory Techniques
By M Allman and D F Lawrence
Arco Publishing Company, Inc
1972 ISBN 0-668-03358-4
Arco Publishing Company writes:
This is the first comprehensive handbook for the geologist, whether amateur or professional, who requires practical information on the basic laboratory techniques essential to the study of geology. It also covers advanced and sophisticated procedures.
The topics described include specimen cutting and grinding, the preparation of thin sections of rock for microscope study, the petrological microscope, microfossil separation from various matrixes, isolation of minerals from mixed powders, moulding and casting methods to reproduce fossils, and modern embedding techniques for specimen display.
The equipment, different methods of working and their results are discussed and compared. In many cases an elementary method using simple equipment is described in addition to the more advanced methods which usually require expensive apparatus.
The text is augmented with nearly 200 illustrations. Of these 48 are in magnificent full color, and include 32 pictures showing the different stages of thin section preparation. The inclusion of a full color interference chart, in an extended, pull-out form, will be of particular value to the laboratory technician.
The authors are experts in the geological techniques and have both held appointments as Chief Technician in the Department of Geolgoy at Queen Mary College, University of London. This eminently practical manual will be indispensable in the laboratory to anyone concerned with geology in the universities, technical colleges and in industry.
Arco Publishing Company, Inc
1972 ISBN 0-668-03358-4
Arco Publishing Company writes:
This is the first comprehensive handbook for the geologist, whether amateur or professional, who requires practical information on the basic laboratory techniques essential to the study of geology. It also covers advanced and sophisticated procedures.
The topics described include specimen cutting and grinding, the preparation of thin sections of rock for microscope study, the petrological microscope, microfossil separation from various matrixes, isolation of minerals from mixed powders, moulding and casting methods to reproduce fossils, and modern embedding techniques for specimen display.
The equipment, different methods of working and their results are discussed and compared. In many cases an elementary method using simple equipment is described in addition to the more advanced methods which usually require expensive apparatus.
The text is augmented with nearly 200 illustrations. Of these 48 are in magnificent full color, and include 32 pictures showing the different stages of thin section preparation. The inclusion of a full color interference chart, in an extended, pull-out form, will be of particular value to the laboratory technician.
The authors are experts in the geological techniques and have both held appointments as Chief Technician in the Department of Geolgoy at Queen Mary College, University of London. This eminently practical manual will be indispensable in the laboratory to anyone concerned with geology in the universities, technical colleges and in industry.
Friday, March 23, 2007
The Cause Of Photoluminescence
(via Wahroongai News, Volume 30, No.5, May 1996) Grahame Brown writes:
Many minerals (gemstones) owe their photoluminescent (fluorescent and phosphorescent) properties to the presence of fluorescence activators in their crystal structure. These activators may be either elemental ionic impurities, metallic radicles, e.g., urinate, or structural defects in the crystal structure. Fluorescence activators function by introducing required properly separated raised energy levels for electrons in the mineral’s crystal structure. It is the presence of these defined energy levels (above the ground state) that will allow the mineral to luminesce when irradiated by short wavelength visible light, ultraviolet and x-ray wavelengths, and cathode rays (accelerated electrons).
Substitution of activator ions into a crystal structure is controlled by both the size (radius) and charge of the substituting ions. If a size or charge mismatch does occur, then smaller size and higher charge will affect ionic substitution in crystal structure.
The energy levels required for luminescence may be either:
- Associated with either a single activator, e.g., the europium ions responsible for the blue fluorescence of fluorite.
- Shared with a second co-activator, e.g., the copper and aluminum impurities in sphalerite that are responsible for its fluorescence.
- Shared between the host mineral and an activator, e.g., the green fluorescence of willemite is the result of shared energy levels between the willemite silicate structure and its manganese activator.
In some minerals, e.g., diamond, non-metals such as nitrogen and hydrogen act as fluorescence activators. While there is no lower limit on the concentration of an activator required to produce fluorescence, typical fluorescence activators are present in quite small concentrations that may vary from 1ppm to several percent. However, higher concentrations of activators can inhibit fluorescence by the process known as concentration quenching. A good example of concentration quenching is provided when the concentration of Cr³+ ions start to absorb their neighbors fluorescent emission, thus eventually quenching the red fluorescence of the ruby. Other causes of fluorescence quenching include heat and the additional presence of ions that poison luminescence.
Certainly fluorescence can be quenched by heat. This occurs because heat increases molecular vibrations in the crystal structure. As a consequence, these additional vibrations can interact with an activator or co-activator (sensitizer) to carry off their luminescence excitation energy as heat.
Fluorescence also can be quenched if certain impurities occur in a mineral that has the potential for photoluminescence. For example, the presence of Fe³+ and to a lesser extent Fe²+ in ruby effectively quenches its fluorescence; for the Fe³+ selectively steals blue to ultraviolet wavelengths from Cr³+ to energize a charge transfer reaction between Fe³+ and its surrounding oxygen atoms. Consequently the Cr³+ ion can’t be energized, and minimal red fluorescence (purely from red and green absorption) will occur.
For more information refer to Robbins, M (1994); Geoscience Press, Phoenix.
Many minerals (gemstones) owe their photoluminescent (fluorescent and phosphorescent) properties to the presence of fluorescence activators in their crystal structure. These activators may be either elemental ionic impurities, metallic radicles, e.g., urinate, or structural defects in the crystal structure. Fluorescence activators function by introducing required properly separated raised energy levels for electrons in the mineral’s crystal structure. It is the presence of these defined energy levels (above the ground state) that will allow the mineral to luminesce when irradiated by short wavelength visible light, ultraviolet and x-ray wavelengths, and cathode rays (accelerated electrons).
Substitution of activator ions into a crystal structure is controlled by both the size (radius) and charge of the substituting ions. If a size or charge mismatch does occur, then smaller size and higher charge will affect ionic substitution in crystal structure.
The energy levels required for luminescence may be either:
- Associated with either a single activator, e.g., the europium ions responsible for the blue fluorescence of fluorite.
- Shared with a second co-activator, e.g., the copper and aluminum impurities in sphalerite that are responsible for its fluorescence.
- Shared between the host mineral and an activator, e.g., the green fluorescence of willemite is the result of shared energy levels between the willemite silicate structure and its manganese activator.
In some minerals, e.g., diamond, non-metals such as nitrogen and hydrogen act as fluorescence activators. While there is no lower limit on the concentration of an activator required to produce fluorescence, typical fluorescence activators are present in quite small concentrations that may vary from 1ppm to several percent. However, higher concentrations of activators can inhibit fluorescence by the process known as concentration quenching. A good example of concentration quenching is provided when the concentration of Cr³+ ions start to absorb their neighbors fluorescent emission, thus eventually quenching the red fluorescence of the ruby. Other causes of fluorescence quenching include heat and the additional presence of ions that poison luminescence.
Certainly fluorescence can be quenched by heat. This occurs because heat increases molecular vibrations in the crystal structure. As a consequence, these additional vibrations can interact with an activator or co-activator (sensitizer) to carry off their luminescence excitation energy as heat.
Fluorescence also can be quenched if certain impurities occur in a mineral that has the potential for photoluminescence. For example, the presence of Fe³+ and to a lesser extent Fe²+ in ruby effectively quenches its fluorescence; for the Fe³+ selectively steals blue to ultraviolet wavelengths from Cr³+ to energize a charge transfer reaction between Fe³+ and its surrounding oxygen atoms. Consequently the Cr³+ ion can’t be energized, and minimal red fluorescence (purely from red and green absorption) will occur.
For more information refer to Robbins, M (1994); Geoscience Press, Phoenix.
Bonnie And Clyde
Memorable quote (s) from the movie:
Bonnie's Mother (Mabel Cavitt): You know Clyde, I read about you all in the papers, and I just get scared.
Clyde Barrow (Warren Beatty): Now Ms. Parker, don't you believe what you read in all them newspapers. That's the law talkin' there. They want us to look big so they gonna look big when they catch us. And they ain't gonna catch us. 'Cause I'm even better at runnin' than I am at robbin' banks! Shoot, if we'd done half that stuff they said we'd done in that paper, we'd be millionaires by now, wouldn't we? But Ms. Parker, this here's the way we know best how to make money. But we gonna be quittin' all this, as soon as the hard times are over. I can tell ya that. Why just the other night, me and Bonnie were talkin'. And we were talkin' about the time we're gonna settle down and get us a home. And uh, she says to me, she says, "You know, I couldn't bear to live more than three miles from my precious Mother." Now how'd ya like that, Mother Parker?
Bonnie's Mother (Mabel Cavitt): I don't believe I would. I surely don't. You try to live three miles from me and you won't live long, honey. You best keep runnin', Clyde Barrow. And you know it. Bye, baby.
Bonnie's Mother (Mabel Cavitt): You know Clyde, I read about you all in the papers, and I just get scared.
Clyde Barrow (Warren Beatty): Now Ms. Parker, don't you believe what you read in all them newspapers. That's the law talkin' there. They want us to look big so they gonna look big when they catch us. And they ain't gonna catch us. 'Cause I'm even better at runnin' than I am at robbin' banks! Shoot, if we'd done half that stuff they said we'd done in that paper, we'd be millionaires by now, wouldn't we? But Ms. Parker, this here's the way we know best how to make money. But we gonna be quittin' all this, as soon as the hard times are over. I can tell ya that. Why just the other night, me and Bonnie were talkin'. And we were talkin' about the time we're gonna settle down and get us a home. And uh, she says to me, she says, "You know, I couldn't bear to live more than three miles from my precious Mother." Now how'd ya like that, Mother Parker?
Bonnie's Mother (Mabel Cavitt): I don't believe I would. I surely don't. You try to live three miles from me and you won't live long, honey. You best keep runnin', Clyde Barrow. And you know it. Bye, baby.
Simulants For Paraiba Tourmalines
Today the 4 different types of simulants for Paraiba tourmaline are still encountered in all shapes and sizes.
(via ICA Early Warning Flash, No.47, September 20, 1991) Deutsche Stiftung Edelsteinforschung writes:
Details
In the last weeks some remarkable simulants for blue and greenish blue Paraiba tourmalines have been observed in Idar Oberstein. In lots of cut stones 4 different types of simulants have been found.
- Blue to greenish blue apatite
- Blue irradiated topaz (unheated)
- Beryl-beryl-triplets with a bright blue cement
- Tourmaline glass doublets
Blue and greenish blue apatite has also been found in lots of rough Paraiba tourmalines.
Identification
1. Apatite possesses refractive indices in the same range as tourmaline but the birefringence is distinctly lower. Furthermore, the absorption spectra are quite different; blue and greenish blue apatite shows absorption lines in the red and yellow, which are caused by certain color centers, while Paraiba tourmalines owe their color to copper and manganese, which cause broad absorption bands in the red and green spectral range.
2. Blue irradiated topaz has lower refractive indices than tourmaline and additionally a lower
birefringence, while the density is higher. The artificial coloration by irradiation has been tested by thermoluminescence measurements.
3. The beryl-beryl-triplets are detectable by the lower refractive indices and birefringence compared to tourmaline. The cementing layer can be easily observed by microscopical studies.
4. The tourmaline-glass-doublets can cause more difficulties because the upper part consists of tourmaline. But microscopical observations attest the composite stone. Routine tests revealed doubling of the back facets of tourmaline and single refraction of glass.
Conclusion
Be careful with lots, and investigate each stone of every lot individually even if or especially when the color is similar or nearly the same.
(via ICA Early Warning Flash, No.47, September 20, 1991) Deutsche Stiftung Edelsteinforschung writes:
Details
In the last weeks some remarkable simulants for blue and greenish blue Paraiba tourmalines have been observed in Idar Oberstein. In lots of cut stones 4 different types of simulants have been found.
- Blue to greenish blue apatite
- Blue irradiated topaz (unheated)
- Beryl-beryl-triplets with a bright blue cement
- Tourmaline glass doublets
Blue and greenish blue apatite has also been found in lots of rough Paraiba tourmalines.
Identification
1. Apatite possesses refractive indices in the same range as tourmaline but the birefringence is distinctly lower. Furthermore, the absorption spectra are quite different; blue and greenish blue apatite shows absorption lines in the red and yellow, which are caused by certain color centers, while Paraiba tourmalines owe their color to copper and manganese, which cause broad absorption bands in the red and green spectral range.
2. Blue irradiated topaz has lower refractive indices than tourmaline and additionally a lower
birefringence, while the density is higher. The artificial coloration by irradiation has been tested by thermoluminescence measurements.
3. The beryl-beryl-triplets are detectable by the lower refractive indices and birefringence compared to tourmaline. The cementing layer can be easily observed by microscopical studies.
4. The tourmaline-glass-doublets can cause more difficulties because the upper part consists of tourmaline. But microscopical observations attest the composite stone. Routine tests revealed doubling of the back facets of tourmaline and single refraction of glass.
Conclusion
Be careful with lots, and investigate each stone of every lot individually even if or especially when the color is similar or nearly the same.
Be On The Lookout For Fake Amber
(via Wahroongai News, Volume 32, Number 3, March 1998) Grahame Brown writes:
This warning follows the recently held North Brisbane Lapidary Show at which one dealer was found to be selling materials clearly marked as amber—yet these materials were not amber. One group of the ambers for sale were manufactured from the amber imitation polyberne; and other pale yellowish ambers were obviously recent copal resin (some of which was attractively included by insect inclusions).
To assist members and students not to be taken in by this scam, the following information is supplied on these two amber imitations and their identification.
Copal Resin
Copal resin is a diaphanous brittle colorless, yellow to brownish recent plant resin that may have an age of up to several tens of thousands of years. Commercial copal resins are often given names such as Kauri gum (a misnomer), Manila, Congo or Colombian copal.
Kauri gum and manila are respectively derived from sap from the gymnosperms Agathis australis from the North Island of New Zealand and Agathis albis from the Philippines and the Indonesian archipelago. There are two major African sources of copal resin which also may be termed congo or Zanzibar resin. East African copal, which comes from Tanzania and island of Zanzibar, is derived from sap exuded from damaged trunks and branches of the leguminous (fruit-bearing) angiosperm (flowering plant) Hymenaea verrucosa; while West African copal from the Congo Republic is derived from the sap of the leguminous angiosperm Copiafera demusi. Most Colombian copal comes from ploughed fields in the Departments of Santander, Boyaca, and Bolivar—specifically near the cities and villages of Bucaramanga, Giron, Bonda, Medellin, Penablanca, Mariquita, and Valle du Jesus. Some Colombian copal has been given the tongue-twisting name of bucarimangite. Age dating of specimens of Colombian copal has yielded ages that ranged from 10 to 500 years. The source resin of Colombian copal is undoubtedly three resin producing trees that are still growing in Colombia—the Hymenaea courbaril, the H. oblongifolia, and the H. parvifolia. In these trees the exuded resin accumulates between the bark and wood, and also under the roots of the tree. Common inclusions in this very recent resin include stingless bees, millipedes, centipedes, ants, moths, beetles, cockroaches, silverfish, and termites.
Precisely how long copal resin takes to convert to amber is unknown. However, this (hardening) time is influenced by such conditions as temperature, pressure, moisture, and perhaps the presence or absence of oxygen. Poinar (1994) suggested that 2-4 million years of burial might be required to convert copal resin into amber.
Copal resin and/or kauri gum are excellent amber look-alikes so with the exception copal’s:
Slightly lower hardness (2 on Mohs scale).
Slightly lower specific gravity (varying from 1.3 to 1.09 with age).
Increased solubility in volatile hydrocarbons.
Increased volatility, with a ‘pine’-like odor being emitted when kauri and/or copal is firmly rubbed in the heel of the hand.
Increased shallow surface crazing, restricted to the outer 2mm of the resin, due to continuing evaporation of volatiles.
………these effective amber imitations have an appearance, gemological properties, sectility (chips on peeling), and pattern of inclusions virtually identical to those of amber.
Practically, the increased solubility of kauri gum/copal resin in volatile organic solvents (a potentially destructive test) may be used to effectively discriminate them from amber, as
1. Surfaces of copal resin become sticky to an applied finger following the judicious application of a drop of volatile organic solvent (e.g. ether, chloroform, acetone, or alcohol) to an inconspicuous area of the suspect resin. This is a very useful test that can be applied before you purchase specimens of ? amber; and,
2. A yellow stain will be deposited on the surface of an alcohol-moistened white cloth or tissue, when an inconspicuous surface of kauri and/or copal is wiped briskly with a moistened cloth or tissue.
Polyberne
Polyberne, a man-made composite imitation of amber consists of fragments of amber embedded in brownish polyester casting resin. Polyberne is a distinctly Polish product that displays evidence of:
- Molding.
- Entrapment of air bubbles between the external surface of the imitation and the mold into which the polyester resin was poured.
- Evidence of two components. That is fragments of amber embedded in a resin of different refractive index.
Hand lens examination, looking for evidence of embedding and molding, and perhaps a test for sectility, are all that is required to positively identify the polyberne imitation of amber.
So beware, these materials are in the marketplace. Do not be caught for want of applying a few simple observations and tests.
This warning follows the recently held North Brisbane Lapidary Show at which one dealer was found to be selling materials clearly marked as amber—yet these materials were not amber. One group of the ambers for sale were manufactured from the amber imitation polyberne; and other pale yellowish ambers were obviously recent copal resin (some of which was attractively included by insect inclusions).
To assist members and students not to be taken in by this scam, the following information is supplied on these two amber imitations and their identification.
Copal Resin
Copal resin is a diaphanous brittle colorless, yellow to brownish recent plant resin that may have an age of up to several tens of thousands of years. Commercial copal resins are often given names such as Kauri gum (a misnomer), Manila, Congo or Colombian copal.
Kauri gum and manila are respectively derived from sap from the gymnosperms Agathis australis from the North Island of New Zealand and Agathis albis from the Philippines and the Indonesian archipelago. There are two major African sources of copal resin which also may be termed congo or Zanzibar resin. East African copal, which comes from Tanzania and island of Zanzibar, is derived from sap exuded from damaged trunks and branches of the leguminous (fruit-bearing) angiosperm (flowering plant) Hymenaea verrucosa; while West African copal from the Congo Republic is derived from the sap of the leguminous angiosperm Copiafera demusi. Most Colombian copal comes from ploughed fields in the Departments of Santander, Boyaca, and Bolivar—specifically near the cities and villages of Bucaramanga, Giron, Bonda, Medellin, Penablanca, Mariquita, and Valle du Jesus. Some Colombian copal has been given the tongue-twisting name of bucarimangite. Age dating of specimens of Colombian copal has yielded ages that ranged from 10 to 500 years. The source resin of Colombian copal is undoubtedly three resin producing trees that are still growing in Colombia—the Hymenaea courbaril, the H. oblongifolia, and the H. parvifolia. In these trees the exuded resin accumulates between the bark and wood, and also under the roots of the tree. Common inclusions in this very recent resin include stingless bees, millipedes, centipedes, ants, moths, beetles, cockroaches, silverfish, and termites.
Precisely how long copal resin takes to convert to amber is unknown. However, this (hardening) time is influenced by such conditions as temperature, pressure, moisture, and perhaps the presence or absence of oxygen. Poinar (1994) suggested that 2-4 million years of burial might be required to convert copal resin into amber.
Copal resin and/or kauri gum are excellent amber look-alikes so with the exception copal’s:
Slightly lower hardness (2 on Mohs scale).
Slightly lower specific gravity (varying from 1.3 to 1.09 with age).
Increased solubility in volatile hydrocarbons.
Increased volatility, with a ‘pine’-like odor being emitted when kauri and/or copal is firmly rubbed in the heel of the hand.
Increased shallow surface crazing, restricted to the outer 2mm of the resin, due to continuing evaporation of volatiles.
………these effective amber imitations have an appearance, gemological properties, sectility (chips on peeling), and pattern of inclusions virtually identical to those of amber.
Practically, the increased solubility of kauri gum/copal resin in volatile organic solvents (a potentially destructive test) may be used to effectively discriminate them from amber, as
1. Surfaces of copal resin become sticky to an applied finger following the judicious application of a drop of volatile organic solvent (e.g. ether, chloroform, acetone, or alcohol) to an inconspicuous area of the suspect resin. This is a very useful test that can be applied before you purchase specimens of ? amber; and,
2. A yellow stain will be deposited on the surface of an alcohol-moistened white cloth or tissue, when an inconspicuous surface of kauri and/or copal is wiped briskly with a moistened cloth or tissue.
Polyberne
Polyberne, a man-made composite imitation of amber consists of fragments of amber embedded in brownish polyester casting resin. Polyberne is a distinctly Polish product that displays evidence of:
- Molding.
- Entrapment of air bubbles between the external surface of the imitation and the mold into which the polyester resin was poured.
- Evidence of two components. That is fragments of amber embedded in a resin of different refractive index.
Hand lens examination, looking for evidence of embedding and molding, and perhaps a test for sectility, are all that is required to positively identify the polyberne imitation of amber.
So beware, these materials are in the marketplace. Do not be caught for want of applying a few simple observations and tests.
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