Writer unknown
There’s a sleepy little township out beyond the western plains,
Lightning Ridge the town of opal, where there’s heat and scanty rains.
The location is not scenic, just rough ridges all round,
Nature strewed scenes of beauty in Black Opal underground.
If you have never seen Black Opal then you have missed a splendid sight,
Like quicksilver gaily colored, slipping through the shades of night.
Though you have roamed the whole world, and seen all there is to see,
There’s scenes you’ve never dreamed of, in this stone of mystery.
Quite unique in all its beauty, as a gem it stands alone,
Mortal man will never fashion imitations of these stones.
As you look into opal, turn it gently and behold,
Vivid shades of blue and crimson, softly turn to green and gold.
Lit by pools of gleaming fire that appears and fade away,
Moving like a motion picture of some long forgotten day.
Here you’ll see a perfect rainbow mirrored in a blue lagoon,
Crimson sunsets, verdant pastures, blending with the rising moon.
Liquid fire in a valley on a dark and stormy night,
Twinkling stars of changing colors, dancing in a golden light.
Storm clouds over tropic splendors, vivid lightning flashes gleam,
There’s scenes that seem to haunt your memory like some half forgotten dream.
Ever restless, ever changing, scene on scene is gently born,
Opening like a glorious flower wet with dew at the flush of dawn.
Flecked with dust of wattle blossoms, branding it Australia’s own,
Beautiful and mystifying Queen of gems, the opal stone.
Tuesday, March 27, 2007
Tootsie
Memorable quote (s) from the movie:
Michael Dorsey (Dustin Hoffman): Thank you, Gordon. Well, I cannot tell you all how deeply moved I am. I never in my wildest dreams imagined that I would be the object of so much genuine affection. It makes it all the more difficult for me to say what I'm now going to say. Yes. I do feel it's time to set the record straight. You see, I didn't come here just as an administrator, Dr. Brewster; I came to this hospital to settle an old score. Now you all know that my father was a brilliant man; he built this hospital. What you don't know is that to his family, he was an unmerciful tyrant - an absolute dodo bird. He drove my mother, his wife, to - to drink; in fact, she - uh, she she she went riding one time and lost all her teeth. The son Edward became a recluse, and the oldest daughter - the pretty one, the charming one - became pregnant when she was fifteen years old and was driven out of the house. In fact, she was so terrified that she would, uh, that, uh, that, that, that the baby daughter would bear the stigma of illegitimacy that she, she - she decided to change her name and she contracted a disfiguring disease... after moving to Tangiers, which is where she raised the, the, the little girl as her sister. But her one ambition in life - besides the child's happiness - was to become a nurse, so she returned to the States and joined the staff right here at Southwest General. Well, she worked here, she knew she had to speak out wherever she saw injustice and inhumanity. God save us, you do understand that, don't you, Dr. Brewster?
John Van Horne (George Gaynes): I never laid a hand on her.
Michael Dorsey (Dustin Hoffman): Yes, you did. And she was shunned by all you nurses, too... and by a, what do you call it, what do you call it, a - something like a pariah, to you doctors who found her idealistic and reckless. But she was deeply, deeply, deeply, deeply, deeply, deeply loved by her brother. It was this brother who, on the day of her death, swore to the good Lord above that he would follow in her footsteps, and, and, and, and, and, and, and, and, and, and, and, just, just, just, just, just, just, just, just, just, just owe it all up to her. But on her terms. As a woman. And just as proud to be a woman as she ever was. For I am not Emily Kimberly, the daughter of Dwayne and Alma Kimberly. No, I'm not. I'm Edward Kimberly, the recluse brother of my sister Anthea. Edward Kimberly, who has finally vindicated his sister's good name. I am Edward Kimberly. Edward Kimberly. And I'm not mentally ill, but proud, and lucky, and strong enough to be the woman that was the best part of my manhood. The best part of myself.
Michael Dorsey (Dustin Hoffman): Thank you, Gordon. Well, I cannot tell you all how deeply moved I am. I never in my wildest dreams imagined that I would be the object of so much genuine affection. It makes it all the more difficult for me to say what I'm now going to say. Yes. I do feel it's time to set the record straight. You see, I didn't come here just as an administrator, Dr. Brewster; I came to this hospital to settle an old score. Now you all know that my father was a brilliant man; he built this hospital. What you don't know is that to his family, he was an unmerciful tyrant - an absolute dodo bird. He drove my mother, his wife, to - to drink; in fact, she - uh, she she she went riding one time and lost all her teeth. The son Edward became a recluse, and the oldest daughter - the pretty one, the charming one - became pregnant when she was fifteen years old and was driven out of the house. In fact, she was so terrified that she would, uh, that, uh, that, that, that the baby daughter would bear the stigma of illegitimacy that she, she - she decided to change her name and she contracted a disfiguring disease... after moving to Tangiers, which is where she raised the, the, the little girl as her sister. But her one ambition in life - besides the child's happiness - was to become a nurse, so she returned to the States and joined the staff right here at Southwest General. Well, she worked here, she knew she had to speak out wherever she saw injustice and inhumanity. God save us, you do understand that, don't you, Dr. Brewster?
John Van Horne (George Gaynes): I never laid a hand on her.
Michael Dorsey (Dustin Hoffman): Yes, you did. And she was shunned by all you nurses, too... and by a, what do you call it, what do you call it, a - something like a pariah, to you doctors who found her idealistic and reckless. But she was deeply, deeply, deeply, deeply, deeply, deeply loved by her brother. It was this brother who, on the day of her death, swore to the good Lord above that he would follow in her footsteps, and, and, and, and, and, and, and, and, and, and, and, just, just, just, just, just, just, just, just, just, just owe it all up to her. But on her terms. As a woman. And just as proud to be a woman as she ever was. For I am not Emily Kimberly, the daughter of Dwayne and Alma Kimberly. No, I'm not. I'm Edward Kimberly, the recluse brother of my sister Anthea. Edward Kimberly, who has finally vindicated his sister's good name. I am Edward Kimberly. Edward Kimberly. And I'm not mentally ill, but proud, and lucky, and strong enough to be the woman that was the best part of my manhood. The best part of myself.
Benitoite
(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.
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.
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.
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