(via ICA Early Warning Flash, No. 32, February 16, 1990) GIA writes:
General background
At one of the gem shows held in Tucson, Arizona, during February of 1990 one exhibitor was offering for sale blue sapphires which were reportedly enhanced with a ‘deep’ diffusion treatment. The authors of this report were shown two plastic bags of reportedly treated material, each containing an estimated several hundred carats of these treated stones. A number of these were purchased for investigation.
Gemological properties
Eleven treated stones were examined. Basic gemological properties—refractive index, birefringence, optic character, Chelsea filter reaction—were all consistent with those reported in the literature for natural blue sapphires.
The color of the stones was fairly uniform, being a medium dark slightly violetish blue. All were very transparent.
None of the stones exhibited any absorption features of the type association with iron-bearing blue sapphires. Three of the stones, however, exhibited a bright fluorescent line centered at 693nm. It is interesting in this regard that the vendor’s promotional flier states that ‘….all stones treated are genuine Ceylon sapphires…’
Key identifying features
Under longwave ultraviolet radiation all but two of the stones were inert; these same stones all fluoresced a weak to moderate, chalky yellowish green to short wave ultraviolet. The other two stones fluoresced a weak to moderate pinkish orange to longwave ultraviolet; the shortwave reaction was similar but weaker in intensity. None of the stones exhibited any phosphorescence.
Magnification and darkfield illumination revealed some features associated with corundum that has been subjected to high temperatures: diffused color banding, broken ‘dot-like’ acicular inclusions, melted included crystals resembling ‘snowballs’ with surrounding spatter halos, and superficial sintering in surface pits. It should be noted that these features were, in general, minor.
Examination using diffused transmitted light without immersion or magnification showed color concentrations along facet junctions and outlining of the girdle edge. Also noted was some variation in color from one facet to another.
Using immersion and diffused transmitted light without magnification the color concentrations along facet junctions and the girdle as well as the uneven facet-to-facet coloration were again noted. In many cases these features were significantly more obvious when immersion was now used.
Suggestion
Diffusion treated sapphires are now being made increasingly available in the market. It this becomes important to use diffused transmitted illumination and immersion in the routine examination of corundum.
Friday, March 30, 2007
The Shawshank Redemption
Memorable quote (s) from the movie:
Andy Dufresne (Tim Robbins): You know what the Mexicans say about the Pacific?
Red (Morgan Freeman): No.
Andy Dufresne (Tim Robbins): They say it has no memory. That's where I want to live the rest of my life. A warm place with no memory.
Andy Dufresne (Tim Robbins): You know what the Mexicans say about the Pacific?
Red (Morgan Freeman): No.
Andy Dufresne (Tim Robbins): They say it has no memory. That's where I want to live the rest of my life. A warm place with no memory.
Hardness Testing Of Gemstones: A Re-evaluation Of The Values
(via Gemmology Queensland, Vol 3, No.1, Jan 2002/IGC Conference Madrid 2001) Michael Gray writes:
Hardness testing is one of the methods that a mineralogist uses to determine the identity of a mineral sample, but which has rarely been used by the gemologist. A mineralogist can usually find some inconspicuous face or broken area to conduct a scratch test, but the gemologist rarely has had a surface on a gemstone to do a comparable test without visible damage to the polish of the stone. However, the ability to choose a random surface may give a false value when a range of hardness exist, as in the case of kyanite, which has a documented variation from 4.5 to 5 on the Moh’s scale of hardness. While a species with such a diverse range can be easy to identify and test, there are many other species that have smaller variations that have not been measured. We are preparing a method of testing hardness during the faceting process. Our present system was developed by Friedrich Mohs in 1822, whereby he set relative values of hardness to ten easily obtainable species for comparison to each other, and measured by making scratches on surfaces of the unknown material with these ten species. This scale is still used as the standard, but variations in hardness has been known since at least 1844 using a device called sclerometer, and researchers were able to deduce objective values, although some variations in these scales are noted, depending upon the method and preparation used. In fact, some researchers determined that topaz is less hard than quartz when the sclerometer was used on powders of these two species.
Lapidaries have always noticed some of these variations in hardness in some species, especially noticeable in heat treated sapphires and rubies. A good example of this variation is the species fresnoite. In the references, the published hardness varies from “3 to 4” to a value of 4.7. A lapidary must rely upon these figures to determine which cutting and polishing laps and media to use in fashioning a gemstone. A great variation in hardness was noticed in the grinding and polishing of the stone, with only one direction being noticeably ‘soft’ as compared to the other facets. There is only one direction being in the range of 4 in hardness, with all other directions being noticeably harder.
These are hardly the only examples to cite; there are many materials, such as spodumene, sillimanite, elbaite, and many of the garnets that exhibit some noticeable variation in hardness during faceting. Diamond cutters know of the variations in their specialty, and use that knowledge in the fashioning of those gems.
The argument could be made that Moh’s scale has worked for almost two centuries, and that there is n need to change this system. That is not the purpose of this study. There are a number of purposes why this study has been initiated to determine the actual hardness of a species, such as fresnoite, where the original description may be inaccurate to document the variation of hardness, as well ad ‘normal’ hardness, within a species. To determine if a variation of hardness may be caused by a man-induced treatment, such as heat treatment of corundum, which then can be used as a way of detecting these treatments. This might also be taken further to determine origin, as well, depending upon impurities, coloring agents, and variations in chemical composition to help clear up conflicting values in different publications to relate these values to the existing Moh’s scale of hardness so that the numbers are understandable to academics and lay persons alike.
Equipment has been developed recently that makes it much easier to conduct hardness testing. The development of ultrasonic indenters that can be calibrated based on the Rockwell and Vickers scales, two of the glass and metal industry’s standards, should eliminate most of the danger of stone breakage during hardness testing. Our testing will be done during the cutting stages, so any noticeable marks made on the softer stones can be polished out.
The ten species used in the Moh’s scale will have been measured, resulting in a set of numbers that will set the parameters for the decimal places between species. Stones are being faceted of these materials to make note of any noticeable variations during cutting, and then measurements taken of these materials. After these values are established, checked, and documented, other species will be faceted, with noticeable hard and soft areas marked for testing. On stones with variable hardnesses, at least four hardness tests will be performed, one each on the ‘softest’ and ‘hardest’ directions, since these normally occur only in one direction, and several tests to establish the ‘normal’ hardness, the hardness over the rest of the material. Therefore, while a range may be established, a third number may represent the general hardness of the material.
The practicality of using gemstones for hardness testing is the general ‘purity’ of the sample being used. Many of the published hardness values were obtained using tiny pieces of the type specimens when they were first discovered and therefore were probably unable to get much accuracy, especially minerals described prior to the 1960s. Unfortunately, once a mineral is named and documented, the values may come up dependent upon the locality and/or if the material has been treated, and all of this information will be documented, as well, whenever possible. Ultimately, we should be able to document the crystal orientation that these variable hardnesses will occur.
There is also an important side benefit to this testing. While hardness testing is only used in a miniscule number of gem identifications, we hope to show that this test can be used in gem labs, using the modern equipment available today. The marks made by a skilled and knowledgeable worker using this modern equipment can be so tiny as to be undetectable by the naked eye, and can be placed on an inconspicuous spot on the girdle or pavilion of the stone. With the values obtained through this research, there will be one more test available for questionable gems. It should also be possible to test mounted stones as well, where refractive indices and specific gravities may not be able to be obtained without removal of the stone from the mounting.
Hardness testing is one of the methods that a mineralogist uses to determine the identity of a mineral sample, but which has rarely been used by the gemologist. A mineralogist can usually find some inconspicuous face or broken area to conduct a scratch test, but the gemologist rarely has had a surface on a gemstone to do a comparable test without visible damage to the polish of the stone. However, the ability to choose a random surface may give a false value when a range of hardness exist, as in the case of kyanite, which has a documented variation from 4.5 to 5 on the Moh’s scale of hardness. While a species with such a diverse range can be easy to identify and test, there are many other species that have smaller variations that have not been measured. We are preparing a method of testing hardness during the faceting process. Our present system was developed by Friedrich Mohs in 1822, whereby he set relative values of hardness to ten easily obtainable species for comparison to each other, and measured by making scratches on surfaces of the unknown material with these ten species. This scale is still used as the standard, but variations in hardness has been known since at least 1844 using a device called sclerometer, and researchers were able to deduce objective values, although some variations in these scales are noted, depending upon the method and preparation used. In fact, some researchers determined that topaz is less hard than quartz when the sclerometer was used on powders of these two species.
Lapidaries have always noticed some of these variations in hardness in some species, especially noticeable in heat treated sapphires and rubies. A good example of this variation is the species fresnoite. In the references, the published hardness varies from “3 to 4” to a value of 4.7. A lapidary must rely upon these figures to determine which cutting and polishing laps and media to use in fashioning a gemstone. A great variation in hardness was noticed in the grinding and polishing of the stone, with only one direction being noticeably ‘soft’ as compared to the other facets. There is only one direction being in the range of 4 in hardness, with all other directions being noticeably harder.
These are hardly the only examples to cite; there are many materials, such as spodumene, sillimanite, elbaite, and many of the garnets that exhibit some noticeable variation in hardness during faceting. Diamond cutters know of the variations in their specialty, and use that knowledge in the fashioning of those gems.
The argument could be made that Moh’s scale has worked for almost two centuries, and that there is n need to change this system. That is not the purpose of this study. There are a number of purposes why this study has been initiated to determine the actual hardness of a species, such as fresnoite, where the original description may be inaccurate to document the variation of hardness, as well ad ‘normal’ hardness, within a species. To determine if a variation of hardness may be caused by a man-induced treatment, such as heat treatment of corundum, which then can be used as a way of detecting these treatments. This might also be taken further to determine origin, as well, depending upon impurities, coloring agents, and variations in chemical composition to help clear up conflicting values in different publications to relate these values to the existing Moh’s scale of hardness so that the numbers are understandable to academics and lay persons alike.
Equipment has been developed recently that makes it much easier to conduct hardness testing. The development of ultrasonic indenters that can be calibrated based on the Rockwell and Vickers scales, two of the glass and metal industry’s standards, should eliminate most of the danger of stone breakage during hardness testing. Our testing will be done during the cutting stages, so any noticeable marks made on the softer stones can be polished out.
The ten species used in the Moh’s scale will have been measured, resulting in a set of numbers that will set the parameters for the decimal places between species. Stones are being faceted of these materials to make note of any noticeable variations during cutting, and then measurements taken of these materials. After these values are established, checked, and documented, other species will be faceted, with noticeable hard and soft areas marked for testing. On stones with variable hardnesses, at least four hardness tests will be performed, one each on the ‘softest’ and ‘hardest’ directions, since these normally occur only in one direction, and several tests to establish the ‘normal’ hardness, the hardness over the rest of the material. Therefore, while a range may be established, a third number may represent the general hardness of the material.
The practicality of using gemstones for hardness testing is the general ‘purity’ of the sample being used. Many of the published hardness values were obtained using tiny pieces of the type specimens when they were first discovered and therefore were probably unable to get much accuracy, especially minerals described prior to the 1960s. Unfortunately, once a mineral is named and documented, the values may come up dependent upon the locality and/or if the material has been treated, and all of this information will be documented, as well, whenever possible. Ultimately, we should be able to document the crystal orientation that these variable hardnesses will occur.
There is also an important side benefit to this testing. While hardness testing is only used in a miniscule number of gem identifications, we hope to show that this test can be used in gem labs, using the modern equipment available today. The marks made by a skilled and knowledgeable worker using this modern equipment can be so tiny as to be undetectable by the naked eye, and can be placed on an inconspicuous spot on the girdle or pavilion of the stone. With the values obtained through this research, there will be one more test available for questionable gems. It should also be possible to test mounted stones as well, where refractive indices and specific gravities may not be able to be obtained without removal of the stone from the mounting.
Elements Of Physical Geology
By James H Zumberge & Clemens A Nelson
John Wiley & Sons, Inc
1976 ISBN 0-471-98674-7
James H Zumberge & Clemens A Nelson writes:
This book is a direct outgrowth of our Elements of Geology, Third Edition. It is intended for a one-term course in physical geology for the nonmajor. Because we think that a historical perspective is essential to the understanding of earth science, a number of items commonly reserved for books on earth history are included in Chapter 6, Geologic Time. To provide for an appreciation of geologic time in the earlier chapters, the geologic time scale is introduced in the first chapter.
Although many recent text have used the exciting developments in sea floor spreading and place tectonics as a theme around which to organize the subject matter of physical geology, we have preferred the more traditional approach for pedagogic reasons. We believe that an investigation of the earth from the inside out provides a better basis on which student can begin to understand his environment. Thus, the first nine chapters deal with the fundamental materials of the earth and its internal characteristics and processes; the following seven chapters deal with processes that have shaped the surface of the earth and provided its infinite variety of topographic forms.
It is also common practice for current texts to devote a single unit to Environmental Geology. We believe that geology has always been a fundamental environmental science and that the subject of the environment, including geologic hazards, is better served by its inclusion in the chapters where it is natural part of the subject under discussion. Thus, the reader will find environmental problems treated in the chapters on volcanoes, earthquakes, climate, landslides, groundwater, rivers, wind, glaciers, oceans, and resources.
The text of most chapters from Elements of Geology has been revised, and new illustrations have been added. The materials can structures of the crust of the earth are treated in chapter 3, Materials of the Earth’s Crust, and chapter 4, Structures of the Earth’s Crust. These subjects were incorporated into a single chapter in Elements of Geology. Chapter 9, Global Tectonics and Mountain Building, has been revised and expanded and includes a historical account of mountain building theories and a detailed account of the new revolution in geology—that of sea floor spreading and plate tectonics. In each of the chapters dealing with surface processes (chapters 10 to 16), examples from the geologic record have been included to illustrate the uniformitarian relationships between present observations and the past record of the earth.
Chapter 17, Resources from the Earth, is new; it incorporates a number of separate discussions from Elements of Geology and current problems of environmental geology and mineral and energy resources.
We are grateful to the people who supplied photographs for this book. We particularly thank Tad Nichols of Tucson, Arizona, for providing many outstanding photographs of geologic features and phenomena. Sources are given for all photographic illustrations except the ones taken by us. We also thank the National Geographic Society for permission to use parts of their colored maps of the Atlantic and Pacific Ocean floors, which appear as Plates V and VI, preceding Chapter 9. Again we thank Derwin Bell of the Department of Geology at the University of Michigan whose excellent illustrations from Elements of Geology have served so well. We also thank Jeanie Martinez of the Department of Geology, University of California, Los Angeles, for several additional illustrations, and Kathyryn Brown at the University of California, Los Angeles, for help in manuscript preparation.
A great many people have made general and specific contributions in the preparation of the book. Our colleagues in the College of Earth Sciences at the University of Arizona, the Department of Geology, University of Nebraska, and the Department of Geology, University of California, Los Angeles, have been especially generous of their expertise. Don Deneck of Wiley has been both a spur and helpful associate during the many stages of preparation. We express our gratitude to our wives, Marilyn Zumberge and Ruth Nelson, for their patience and understanding while this book was being written.
John Wiley & Sons, Inc
1976 ISBN 0-471-98674-7
James H Zumberge & Clemens A Nelson writes:
This book is a direct outgrowth of our Elements of Geology, Third Edition. It is intended for a one-term course in physical geology for the nonmajor. Because we think that a historical perspective is essential to the understanding of earth science, a number of items commonly reserved for books on earth history are included in Chapter 6, Geologic Time. To provide for an appreciation of geologic time in the earlier chapters, the geologic time scale is introduced in the first chapter.
Although many recent text have used the exciting developments in sea floor spreading and place tectonics as a theme around which to organize the subject matter of physical geology, we have preferred the more traditional approach for pedagogic reasons. We believe that an investigation of the earth from the inside out provides a better basis on which student can begin to understand his environment. Thus, the first nine chapters deal with the fundamental materials of the earth and its internal characteristics and processes; the following seven chapters deal with processes that have shaped the surface of the earth and provided its infinite variety of topographic forms.
It is also common practice for current texts to devote a single unit to Environmental Geology. We believe that geology has always been a fundamental environmental science and that the subject of the environment, including geologic hazards, is better served by its inclusion in the chapters where it is natural part of the subject under discussion. Thus, the reader will find environmental problems treated in the chapters on volcanoes, earthquakes, climate, landslides, groundwater, rivers, wind, glaciers, oceans, and resources.
The text of most chapters from Elements of Geology has been revised, and new illustrations have been added. The materials can structures of the crust of the earth are treated in chapter 3, Materials of the Earth’s Crust, and chapter 4, Structures of the Earth’s Crust. These subjects were incorporated into a single chapter in Elements of Geology. Chapter 9, Global Tectonics and Mountain Building, has been revised and expanded and includes a historical account of mountain building theories and a detailed account of the new revolution in geology—that of sea floor spreading and plate tectonics. In each of the chapters dealing with surface processes (chapters 10 to 16), examples from the geologic record have been included to illustrate the uniformitarian relationships between present observations and the past record of the earth.
Chapter 17, Resources from the Earth, is new; it incorporates a number of separate discussions from Elements of Geology and current problems of environmental geology and mineral and energy resources.
We are grateful to the people who supplied photographs for this book. We particularly thank Tad Nichols of Tucson, Arizona, for providing many outstanding photographs of geologic features and phenomena. Sources are given for all photographic illustrations except the ones taken by us. We also thank the National Geographic Society for permission to use parts of their colored maps of the Atlantic and Pacific Ocean floors, which appear as Plates V and VI, preceding Chapter 9. Again we thank Derwin Bell of the Department of Geology at the University of Michigan whose excellent illustrations from Elements of Geology have served so well. We also thank Jeanie Martinez of the Department of Geology, University of California, Los Angeles, for several additional illustrations, and Kathyryn Brown at the University of California, Los Angeles, for help in manuscript preparation.
A great many people have made general and specific contributions in the preparation of the book. Our colleagues in the College of Earth Sciences at the University of Arizona, the Department of Geology, University of Nebraska, and the Department of Geology, University of California, Los Angeles, have been especially generous of their expertise. Don Deneck of Wiley has been both a spur and helpful associate during the many stages of preparation. We express our gratitude to our wives, Marilyn Zumberge and Ruth Nelson, for their patience and understanding while this book was being written.
The Founders Of Geology
By Sir Andrew Geikie
Dover Publications, Inc
1962
Dover Publication writes:
The later half of the 19th century and the first two decades of the 20th century are especially interesting to students of geology, for it was during those seventy years that the main modern foundations of the science were laid. This book surveys the high moments and central figures in that era of seminal geological activity.
It recounts the story of the progress of geological ideas by reviewing the careers of some of the leaders by whom the progress was chiefly effected, giving full consideration to the lives and work of these major figures, and indicating in the process how geological ideas arose and were slowly worked out into the forms which they now wear. Some of the men whose careers and contributions are examined are Palissy, Guettard, Desmarest, Pallas, De Saussure, Arduino, Lehman, Fuchsel, Werner, Hutton, Playfair, Sir James Hall, Giraud-Soulavie, Cuvier, Michell, Lyell, Logan, Darwin, Agassiz, Nicol, and others.
The author discusses such matters as geological ideas among the Greeks and Romans; growth of geological ideas in the Middle Ages; scientific cosmogonists—Descartes and Leibnitz; the rise of geology in France; the foundation of volcanic geology; the rise of geological travel; the history of the doctrine of geological succession; the Wernerian school of geology; the rise of the modern conception of the theory of the earth; the birth of experimental geology; the rise of stratigraphical geology and paleontology; early teachers and textbooks; the transition or Greywacke formation resolved into the Cambrian, Silurian and Devonian systems; the primordial fauna of Barrande; the pre-Cambrian rocks first begun to be set in order; the influence of Darwin; adoption of zonal stratigraphy of fossiliferous rocks; the rise of glacial geology; the development of geological map-making in Europe and North America; the rise of petrographical geology; and other related topics.
Dover Publications, Inc
1962
Dover Publication writes:
The later half of the 19th century and the first two decades of the 20th century are especially interesting to students of geology, for it was during those seventy years that the main modern foundations of the science were laid. This book surveys the high moments and central figures in that era of seminal geological activity.
It recounts the story of the progress of geological ideas by reviewing the careers of some of the leaders by whom the progress was chiefly effected, giving full consideration to the lives and work of these major figures, and indicating in the process how geological ideas arose and were slowly worked out into the forms which they now wear. Some of the men whose careers and contributions are examined are Palissy, Guettard, Desmarest, Pallas, De Saussure, Arduino, Lehman, Fuchsel, Werner, Hutton, Playfair, Sir James Hall, Giraud-Soulavie, Cuvier, Michell, Lyell, Logan, Darwin, Agassiz, Nicol, and others.
The author discusses such matters as geological ideas among the Greeks and Romans; growth of geological ideas in the Middle Ages; scientific cosmogonists—Descartes and Leibnitz; the rise of geology in France; the foundation of volcanic geology; the rise of geological travel; the history of the doctrine of geological succession; the Wernerian school of geology; the rise of the modern conception of the theory of the earth; the birth of experimental geology; the rise of stratigraphical geology and paleontology; early teachers and textbooks; the transition or Greywacke formation resolved into the Cambrian, Silurian and Devonian systems; the primordial fauna of Barrande; the pre-Cambrian rocks first begun to be set in order; the influence of Darwin; adoption of zonal stratigraphy of fossiliferous rocks; the rise of glacial geology; the development of geological map-making in Europe and North America; the rise of petrographical geology; and other related topics.
Thursday, March 29, 2007
Manufacturing, Production, And Trade Of Synthetic And Enhanced Gems In Modern Russia
(via Gemmology Queensland, Vol 3, No.1, Jan 2002/IGC Conference Madrid 2001) Vladimir S Balitsky writes:
Synthetic gems
In modern Russia in industrial scales practically all kinds and varieties of synthetic analogues of natural gems are produced as well as it was in former USSR. Moreover, crystals of the whole row of compounds having no analogues in nature but possessing properties of gems are synthesized. A list of all synthetic gems produced at present in Russia is given in Table 1 with methods of their obtaining approximate volumes of production and their prices. As can be seen, leuco-sapphire, ruby and sapphires are produced in large quantities. They are grown mainly from the melt by the methods of Verneuil, Czochralski, Kyropulus and Zone melting. Lately they have been grown in small quantities by hydrothermal and flux methods. Traditional Russian synthetic gems also include quartz and its colored varieties especially amethyst, citrine, blue and green quartz. Lately they have developed new technologies of producing two colored amethyst-citrine quartz (ametrine), pink transparent phosphorous-bearing quartz and unusual copper-bearing aventurine in small quantities. Under artificial conditions drusses of both colorless and colored quartz are also grown.
Table 1
Synthetic gems produced in Russia at present
Name: Alexandrite
Growth technique: Czochralski
Approximate production/kg per year: up to one hundred
Approximate price of raw material (US$/per kg): 1000 – 7500
Name: Alexandrite
Growth technique: Flux
Approximate production/kg per year: a few kg’s
Approximate price of raw material (US$/per kg): 1000 – 7500
Name: Amethyst
Growth technique: Hydrothermal
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 50 – 150
Name: Ametrine
Growth technique: Hydrothermal
Approximate production/kg per year: a few hundred
Approximate price of raw material (US$/per kg): 100 - 150
Name: Aquamarine
Growth technique: Hydrothermal/Flux
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 3000 – 5000
Name: Cubic Zirconium Oxide (CZ)
Growth technique: Skull Melting
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 30 – 60
Name: Diamond
Growth technique: HPHT
Approximate production/kg per year: up to 2
Approximate price of raw material (US$/per kg): 1000000
Name: Emerald
Growth technique: Hydrothermal / Flux
Approximate production/kg per year: up to 50
Approximate price of raw material (US$/per kg): 5000 – 7500
Name: Emerald Drusses
Growth technique: Flux
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 1000 – 15000
Name: Forsterite
Growth technique: Czochralski
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 5000
Name: Gadolium Gallium Garnet (GGG)
Growth technique: Czochralski
Approximate production/kg per year: a few dozen
Approximate price of raw material (US$/per kg): 10000
Name: Leuco sapphire
Growth technique: Czochralski
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 350 - 400
Name: Leuco sapphire
Growth technique: Vernueil
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 250 – 300
Name: Leuco sapphire
Growth technique: Kyropulus
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 350 - 400
Name: Leuco sapphire
Growth technique: Horizontal Zoning Melt
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 400 – 500
Name: Morganite
Growth technique: Hydrothermal / Flux
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 3000 – 7000
Name: Malachite
Growth technique: Chemical precipitation from aqueous solutions
Approximate production/kg per year: up to thousand
Approximate price of raw material (US$/per kg): 40 -70
Name: Moissanite
Growth technique: High pressure sublimation
Approximate production/kg per year: a few dozen
Approximate price of raw material (US$/per kg): 25000 – 50000
Name: Opal noble
Growth technique: Chemical precipitation + impregnation by plastic or zirconium hydroxide or silica + high temperature treatment
Approximate production/kg per year: a few dozen
Approximate price of raw material (US$/per kg): 20000 – 35000
Name: Quartz colorless
Growth technique: Hydrothermal
Approximate production/kg per year: a few hundreds of thousands
Approximate price of raw material (US$/per kg): 40 – 600
Name: Quartz colored (yellow, green, blue, brown, smoky, milky)
Growth technique: Hydrothermal
Approximate production/kg per year: a few hundreds of thousands
Approximate price of raw material (US$/per kg): 40 – 80
Name: Quartz pink (transparent)
Growth technique: Hydrothermal
Approximate production/kg per year: a few dozens
Approximate price of raw material (US$/per kg): 3000 - 5000
Name: Quartz drusses
Growth technique: Hydrothermal
Approximate production/kg per year: a few dozens
Approximate price of raw material (US$/per kg): 50 – 100
Name: Ruby
Growth technique: Vernueil / Czochralski / Horizontal Zoning Melt
Approximate production/kg per year: a few thousands
Approximate price of raw material (US$/per kg): 250 – 1000
Name: Ruby
Growth technique: Hydrothermal
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 5000 - 10000
Name: Sapphire
Growth technique: Verneuil / Czochralski
Approximate production/kg per year: a few thousands
Approximate price of raw material (US$/per kg): 250 – 1000
Name: Sapphire
Growth technique: Hydrothermal
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 5000 – 10000
Name: Spinel
Growth technique: Flux
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 25000
Name: Spinel drusses
Growth technique: Flux
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 25000
Name: Turquoise
Growth technique: Chemical precipitation + high pressure treatment
Approximate production/kg per year: a few hundreds
Approximate price of raw material (US$/per kg): 50 – 80
Name: Yttrium Aluminum Garnet (YAG) (Colorless and colored)
Growth technique: Czochralski / Horizontal Zone Melting
Approximate production/kg per year: a few thousands
Approximate price of raw material (US$/per kg): 400 – 700
Name: Zincate
Growth technique: Hydrothermal
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 30000
An essential role in the production of synthetic gems in modern Russia belongs to emerald. It is mainly grown under hydrothermal conditions, but in small quantities it is obtained from flux. Besides emerald, other colored varieties of beryl are grown in very limited quantities. Among other popular synthetic gems grown in Russia, one should notice alexandrite and spinel. First, it was grown by Czochralski and flux methods, and then by Verneuil and flux. The most precious of them are crystals grown from flux. Among other synthetic gems, refined black and white noble opal is also produced. The material may look very similar to the natural opal. Synthetic malachite has also been produced successfully. A considerable progress has been made in the synthesis of large diamonds (yellow, blue and colorless) with the maximum weight up to 5 ct. Within the last two years synthetic moissanite has also been produced. However both synthetic diamonds and synthetic moissanites are produced in rather restricted quantities.
Enhanced gems
Many gems found and imported into Russia (corundum, topaz, quartz, garnet, danburite, scapolite, beryl, tourmaline, turquoise, coral, charoite, lazurite, agates etc.) are of low quality. The gems are often subjected to enhancement with the purpose of increasing their quality. Table 2 gives a list of stones with indicative treatments.
Name: Agate (chalcedony)
Enhancement process: impregnation / heat treatment / irradiation
Enhancement effect: pale colors to yellow, brown, green, blue, black and red; pale colors to brown and red; change of color to dark gray.
Name: Amazonite
Enhancement process: heat treatment / dyeing
Enhancement effect: improvement of color
Name: Amber
Enhancement process: reconstruction / heat treatment / pressing
Enhancement effect: augmentation of weight; improvement of inner structure with induced cracking; augmentation of weight
Name: Charoite
Enhancement process: dyeing
Enhancement effect: improvement of color
Name: Corundum (colorless and colored)
Enhancement process: heat treatment / heat treatment with diffusion / surface coating
Enhancement effect: colorless and pale colors to blue
Name: Danburite
Enhancement process: irradiation / heat treatment
Enhancement effect: remove colorless to brownish—pink / fading
Name: Heliodor
Enhancement process: heat treatment
Enhancement effect: remove yellow to blue (aquamarine)
Name: Lazurite
Enhancement process: impregnation / heat treatment
Enhancement effect: improvement of color
Name: Nephrite
Enhancement process: hydrothermal treatment / irradiation
Enhancement effect: lightening of dark green color to white / darkening of green and brown to black
Name: Quartz
Enhancement process: heat treatment / irradiation / surface coating
Enhancement effect: dark smoky to pale smoky or greenish yellow or colorless / colorless and pale colors to smoky or greenish yellow / colorless and pale colors to pink or blue
Name: Radonite
Enhancement process: dyeing
Enhancement effect: improvement of color
Name: Topaz
Enhancement process: irradiation / irradiation + heat treatment
Enhancement effect: colorless and pale colors to yellow brown or reddish brown / colorless or brown to brownish green or blue / brown or orange to pink / brown or green or blue to colorless
Name: Turquoise
Enhancement process: impregnation under high temperature and high pressure
Enhancement effect: improvement of color / rise of hardness
Synthetic gems
In modern Russia in industrial scales practically all kinds and varieties of synthetic analogues of natural gems are produced as well as it was in former USSR. Moreover, crystals of the whole row of compounds having no analogues in nature but possessing properties of gems are synthesized. A list of all synthetic gems produced at present in Russia is given in Table 1 with methods of their obtaining approximate volumes of production and their prices. As can be seen, leuco-sapphire, ruby and sapphires are produced in large quantities. They are grown mainly from the melt by the methods of Verneuil, Czochralski, Kyropulus and Zone melting. Lately they have been grown in small quantities by hydrothermal and flux methods. Traditional Russian synthetic gems also include quartz and its colored varieties especially amethyst, citrine, blue and green quartz. Lately they have developed new technologies of producing two colored amethyst-citrine quartz (ametrine), pink transparent phosphorous-bearing quartz and unusual copper-bearing aventurine in small quantities. Under artificial conditions drusses of both colorless and colored quartz are also grown.
Table 1
Synthetic gems produced in Russia at present
Name: Alexandrite
Growth technique: Czochralski
Approximate production/kg per year: up to one hundred
Approximate price of raw material (US$/per kg): 1000 – 7500
Name: Alexandrite
Growth technique: Flux
Approximate production/kg per year: a few kg’s
Approximate price of raw material (US$/per kg): 1000 – 7500
Name: Amethyst
Growth technique: Hydrothermal
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 50 – 150
Name: Ametrine
Growth technique: Hydrothermal
Approximate production/kg per year: a few hundred
Approximate price of raw material (US$/per kg): 100 - 150
Name: Aquamarine
Growth technique: Hydrothermal/Flux
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 3000 – 5000
Name: Cubic Zirconium Oxide (CZ)
Growth technique: Skull Melting
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 30 – 60
Name: Diamond
Growth technique: HPHT
Approximate production/kg per year: up to 2
Approximate price of raw material (US$/per kg): 1000000
Name: Emerald
Growth technique: Hydrothermal / Flux
Approximate production/kg per year: up to 50
Approximate price of raw material (US$/per kg): 5000 – 7500
Name: Emerald Drusses
Growth technique: Flux
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 1000 – 15000
Name: Forsterite
Growth technique: Czochralski
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 5000
Name: Gadolium Gallium Garnet (GGG)
Growth technique: Czochralski
Approximate production/kg per year: a few dozen
Approximate price of raw material (US$/per kg): 10000
Name: Leuco sapphire
Growth technique: Czochralski
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 350 - 400
Name: Leuco sapphire
Growth technique: Vernueil
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 250 – 300
Name: Leuco sapphire
Growth technique: Kyropulus
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 350 - 400
Name: Leuco sapphire
Growth technique: Horizontal Zoning Melt
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 400 – 500
Name: Morganite
Growth technique: Hydrothermal / Flux
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 3000 – 7000
Name: Malachite
Growth technique: Chemical precipitation from aqueous solutions
Approximate production/kg per year: up to thousand
Approximate price of raw material (US$/per kg): 40 -70
Name: Moissanite
Growth technique: High pressure sublimation
Approximate production/kg per year: a few dozen
Approximate price of raw material (US$/per kg): 25000 – 50000
Name: Opal noble
Growth technique: Chemical precipitation + impregnation by plastic or zirconium hydroxide or silica + high temperature treatment
Approximate production/kg per year: a few dozen
Approximate price of raw material (US$/per kg): 20000 – 35000
Name: Quartz colorless
Growth technique: Hydrothermal
Approximate production/kg per year: a few hundreds of thousands
Approximate price of raw material (US$/per kg): 40 – 600
Name: Quartz colored (yellow, green, blue, brown, smoky, milky)
Growth technique: Hydrothermal
Approximate production/kg per year: a few hundreds of thousands
Approximate price of raw material (US$/per kg): 40 – 80
Name: Quartz pink (transparent)
Growth technique: Hydrothermal
Approximate production/kg per year: a few dozens
Approximate price of raw material (US$/per kg): 3000 - 5000
Name: Quartz drusses
Growth technique: Hydrothermal
Approximate production/kg per year: a few dozens
Approximate price of raw material (US$/per kg): 50 – 100
Name: Ruby
Growth technique: Vernueil / Czochralski / Horizontal Zoning Melt
Approximate production/kg per year: a few thousands
Approximate price of raw material (US$/per kg): 250 – 1000
Name: Ruby
Growth technique: Hydrothermal
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 5000 - 10000
Name: Sapphire
Growth technique: Verneuil / Czochralski
Approximate production/kg per year: a few thousands
Approximate price of raw material (US$/per kg): 250 – 1000
Name: Sapphire
Growth technique: Hydrothermal
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 5000 – 10000
Name: Spinel
Growth technique: Flux
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 25000
Name: Spinel drusses
Growth technique: Flux
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 25000
Name: Turquoise
Growth technique: Chemical precipitation + high pressure treatment
Approximate production/kg per year: a few hundreds
Approximate price of raw material (US$/per kg): 50 – 80
Name: Yttrium Aluminum Garnet (YAG) (Colorless and colored)
Growth technique: Czochralski / Horizontal Zone Melting
Approximate production/kg per year: a few thousands
Approximate price of raw material (US$/per kg): 400 – 700
Name: Zincate
Growth technique: Hydrothermal
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 30000
An essential role in the production of synthetic gems in modern Russia belongs to emerald. It is mainly grown under hydrothermal conditions, but in small quantities it is obtained from flux. Besides emerald, other colored varieties of beryl are grown in very limited quantities. Among other popular synthetic gems grown in Russia, one should notice alexandrite and spinel. First, it was grown by Czochralski and flux methods, and then by Verneuil and flux. The most precious of them are crystals grown from flux. Among other synthetic gems, refined black and white noble opal is also produced. The material may look very similar to the natural opal. Synthetic malachite has also been produced successfully. A considerable progress has been made in the synthesis of large diamonds (yellow, blue and colorless) with the maximum weight up to 5 ct. Within the last two years synthetic moissanite has also been produced. However both synthetic diamonds and synthetic moissanites are produced in rather restricted quantities.
Enhanced gems
Many gems found and imported into Russia (corundum, topaz, quartz, garnet, danburite, scapolite, beryl, tourmaline, turquoise, coral, charoite, lazurite, agates etc.) are of low quality. The gems are often subjected to enhancement with the purpose of increasing their quality. Table 2 gives a list of stones with indicative treatments.
Name: Agate (chalcedony)
Enhancement process: impregnation / heat treatment / irradiation
Enhancement effect: pale colors to yellow, brown, green, blue, black and red; pale colors to brown and red; change of color to dark gray.
Name: Amazonite
Enhancement process: heat treatment / dyeing
Enhancement effect: improvement of color
Name: Amber
Enhancement process: reconstruction / heat treatment / pressing
Enhancement effect: augmentation of weight; improvement of inner structure with induced cracking; augmentation of weight
Name: Charoite
Enhancement process: dyeing
Enhancement effect: improvement of color
Name: Corundum (colorless and colored)
Enhancement process: heat treatment / heat treatment with diffusion / surface coating
Enhancement effect: colorless and pale colors to blue
Name: Danburite
Enhancement process: irradiation / heat treatment
Enhancement effect: remove colorless to brownish—pink / fading
Name: Heliodor
Enhancement process: heat treatment
Enhancement effect: remove yellow to blue (aquamarine)
Name: Lazurite
Enhancement process: impregnation / heat treatment
Enhancement effect: improvement of color
Name: Nephrite
Enhancement process: hydrothermal treatment / irradiation
Enhancement effect: lightening of dark green color to white / darkening of green and brown to black
Name: Quartz
Enhancement process: heat treatment / irradiation / surface coating
Enhancement effect: dark smoky to pale smoky or greenish yellow or colorless / colorless and pale colors to smoky or greenish yellow / colorless and pale colors to pink or blue
Name: Radonite
Enhancement process: dyeing
Enhancement effect: improvement of color
Name: Topaz
Enhancement process: irradiation / irradiation + heat treatment
Enhancement effect: colorless and pale colors to yellow brown or reddish brown / colorless or brown to brownish green or blue / brown or orange to pink / brown or green or blue to colorless
Name: Turquoise
Enhancement process: impregnation under high temperature and high pressure
Enhancement effect: improvement of color / rise of hardness
Tootsie
Memorable quote (s) from the movie:
Michael Dorsey (Dustin Hoffman): Are you saying that nobody in New York will work with me?
George Fields (Sydney Pollack): No, no, that's too limited... nobody in Hollywood wants to work with you either. I can't even send you up for a commercial. You played a tomato for 30 seconds - they went a half a day over schedule because you wouldn't sit down.
Michael Dorsey (Dustin Hoffman): Yes - it wasn't logical.
George Fields (Sydney Pollack): You were a tomato. A tomato doesn't have logic. A tomato can't move.
Michael Dorsey (Dustin Hoffman): That's what I said. So if he can't move, how's he gonna sit down, George? I was a stand-up tomato: a juicy, sexy, beefsteak tomato. Nobody does vegetables like me. I did an evening of vegetables off-Broadway. I did the best tomato, the best cucumber... I did an endive salad that knocked the critics on their ass.
Michael Dorsey (Dustin Hoffman): Are you saying that nobody in New York will work with me?
George Fields (Sydney Pollack): No, no, that's too limited... nobody in Hollywood wants to work with you either. I can't even send you up for a commercial. You played a tomato for 30 seconds - they went a half a day over schedule because you wouldn't sit down.
Michael Dorsey (Dustin Hoffman): Yes - it wasn't logical.
George Fields (Sydney Pollack): You were a tomato. A tomato doesn't have logic. A tomato can't move.
Michael Dorsey (Dustin Hoffman): That's what I said. So if he can't move, how's he gonna sit down, George? I was a stand-up tomato: a juicy, sexy, beefsteak tomato. Nobody does vegetables like me. I did an evening of vegetables off-Broadway. I did the best tomato, the best cucumber... I did an endive salad that knocked the critics on their ass.
Natural And HPHT-annealed Pink And Blue Diamonds
(via Gemmology Queensland, Vol 3, No.1, Jan 2002/IGC Conference Madrid 2001) George Bosshart writes:
The Gubelin Gem Lab engaged in a new study of HPHT-annealed specimens in order to elaborate criteria for the separation of the fancy diamond colors produced by the General Electric Company from the natural pink and blue colors. The key characteristics of the natural colors are briefly outlined and first indicators for HPHT treatment detection are given below.
Natural pink colors exist in both type Ia and type IIa diamond but exhibit a wider color variety in the first group. Type Ia diamond is found in pure pink to red to purple hues but pink and red are more frequently combined with orange and brown color modifiers. Type IIa diamond is limited to light pink to pink hues which may be modified by secondary orange or brown colors. Red hues do not occur in this group but purple does, as a rare and subordinate modifier at least.
In our natural pink study group of over 100 gem quality diamonds, 75% belonged to type Ia, 2% to the mixed type IbIaA, and 22% to type IIa (of which 15% revealed nitrogen-free infrared survey spectra, whereas 7% showed trace amounts of nitrogen as A or B aggregates or as single nitrogen).
In pink type Ia diamond in particular, an irregular color lamination and patchiness can frequently be observed under magnification. These obvious disturbances are plausibly interpreted as being caused by internal plastic deformation which itself is a reaction of the diamond structure to the impact of geotectonic shear stress (active during orogenetic phases), thus avoiding breakage. However, the cause for the pink color center, a wideband absorption centered at 560nm (2.2 eV), is not known in detail.
The strength of the 560nm absorption band determines the intensity of the type Ia pink color. Pink changes to red or purple when this band reaches higher amplitudes (with absorption coefficients in the order of 0.6 cm¯¹ and above). Nitrogen contents in the form of A and/or B aggregates vary in natural pink diamond from extremely small (in type IIa) to extremely large. In type Ia diamond, hydrogen may be present as well, however, in minor to moderate amounts only. Type IIa diamond features the same 560 nm absorption system and an identical but limited intensity relationship (mentioned above). It follows that neither nitrogen nor hydrogen impurities cause the pink color.
In pink diamond, a slight increase of the general absorption in the blue to violet regions of the spectrum results in an orange color modifier which in turn may alter to a brown modifier when the underlying absorption rises more strongly. This absorption is caused by another, equally unknown type of structural defect in the diamond crystal lattice.
In addition to the above color centers, N3 and H3 absorption in type Ia diamond may add a yellowish to orangy modifier component when present in some strength. This combination is typically encountered in Argyle and Brazilian brownish to purplish pink and red diamond. A rarely occurring 480nm absorption band adds a pure orange component to pink diamond colors.
Natural blue diamond varies less than in hue than pink color group. The only modifier of importance is gray. Natural blue occurs in type IIb diamond exclusively (rare specimens being gray violet rather than blue and belonging to hydrogen-rich type IaB). Type IIb diamond is an electric semiconductor due to the substitution of carbon atoms by ppb amounts of boron on the lattice sites of diamond.
The absorption diagram of blue diamond is characterized by a unique mid-infrared absorption superimposed n the inherent diamond absorption in the two-phonon region, with lesser absorption in the adjacent one and three phonon areas. The strongest absorption band is situated at 2802 wavenumbers. It is also typical for blue diamond that the absorption level steadily decreases from the mid-infrared through the near-infrared and visible regions into the ultraviolet part of the electromagnetic spectrum without showing any absorption bands. The absorption minima of blue diamonds fluctuate from 240nm at the base of the fundamental absorption edge to about 500nm. This variation does have an influence on the exact hue of the blue colors which may range from violetish to slightly greenish blue. The dominant wavelengths, as determined by colorimetric measurement, lie in the 465 to 495nm region and confirm that the primary hue is blue. Only one specimen was encountered so far with a dominant wavelength of 435nm corresponding to a violet-blue hue.
The hues of type IIb diamonds frequently are not easy to determine visually due to their weak color saturations and relatively high tones. The type IIb infrared absorption, e.g. the 2802 wn band, could serve as an indicator for the saturation of blue since it is related to the boron content. However, the absorption coefficient of this and other MIR absorption bands for some reason does not appear to be straightforward measure of the blue saturation of type IIb diamond. When the general absorption in type IIb diamond rises to higher levels, and this is particularly important in the visible part of the spectrum, the color impression shifts to bluish gray and even to neutral gray colors (44% of the blue group of 75 specimens grade blue, 40% mixed blue to gray, 8% neutral gray and 1% violet blue).
There is a small proportion (7%) of type IIb diamonds which possesses an increased absorption in the entire ultraviolet region. Accordingly their absorption minimum is more pronounced than in the pure blue colors and shifts into the center of the visible region, with dominant wavelengths ranging from about 500 to slightly over 600nm. Such diamonds essentially appear gray with a greenish to yellowish color modifier. It is interesting to note that greenish gray and yellowish gray colors also occur in type Ia diamond, showing high B nitrogen aggregate and high hydrogen contents, respectively high A aggregate and H contents.
The presence of gray color modifier in type IIb blue diamond may be interpreted as a color generated by the combination of boron with single nitrogen or other chemical impurities and/or by structural defects. However, gray color may also be independent of boron traces at all. A very weak 270 nm band was encountered in several natural blue diamonds and is allocated to single nitrogen.
HPHT Pink and Blue
Prior to 1999, it may have appeared inconceivable that natural off-color diamonds could be improved to obtain the best colors known (D to H color grades), i.e. colorlessness. However, the General Electric Company successfully achieved this breakthrough by applying a modified version of the high pressure/high temperature technology used to grow synthetic diamonds. Since the turn of the millennium, GE has been marketing these virtually colorless diamonds predominantly on the American market and under the brand name, Bellataire (formerly GE POL).
Fancy pink and blue diamond colors are described ad desirable as the white ones. As a consequence, the production of pink and blue became the second great challenge and in 2000. GE managed to add convincing pink and blue color replicas to the wide range of already existing treated diamond colors. In contrast to those irradiated and annealed pink to purple and irradiated blue to green diamond colors, General Electric’s latest products look entirely natural. The exact starting material and its abundance will not be made public by GE. However, experience gained in our study of GE POL diamonds before and after HPHT-annealing (Smith et. al 2000) tells us that the potentially improvable diamond rough must be restricted to type IIa brown respectively type IIB gray to brown specimens of fairly high clarity grades. This implies that the number of diamonds HPHT-annealable to pink and blue colors is considerably inferior to that of the colorless type IIa specimens and that most of the enhanced fancy colors may be low in intensity. A preliminary sampling consisted of six (0.14 to 8.55 ct) pink and two (0.21 and 0.27 ct) blue diamonds HPHT-annealed by GE. The pink stones investigated evidenced that only type IIa and near-type IIa diamonds had been selected. Colorimetric data showed that the resulting pink and blue hues are well within the range of their natural type IIa resp. IIb counterparts. Red or strong blue colors were not observed in this batch, but it included light to intense pink to purple pink colors plus one faint blue and one medium blue specimen each. Brown resp. gray modifiers were subordinate. At this moment, it is safe to state that, comparable to colorless Bellataire diamonds, gemological standard methods (microscopy, UV fluorescence etc.) will not permit a safe separation of natural and HPHT-annealed type IIa pink and semi-conductive blue diamonds. The mid-infrared and UV/VIS spectra of five (out of six) pink samples revealed nitrogen (A or B aggregates, N3 and N9 centers), however, in trace amounts only. The spectra of the blue specimens were very similar to those of the natural colors as well.
Among the optical techniques, Raman photo-luminescence with He/Cd and an Arion laser offer the most promising results. The color enhanced diamonds showed a smaller number of PL bands than recorded for natural colors and the intensities of the bands also differed noticeably. As an example, the 575nm and 637nm bands of the Nº and N centers respectively were definitely stronger than in natural pink diamonds. More and improved criteria are to be expected for both color groups from a larger data base. Advanced testing methods such as X-ray topography or cathodoluminescence applied during our former investigation of eleven colorless diamonds before and after HPHT processing by GE were not used for reasons of limited time and absence of diamonds selected to be processed.
What can be expected as the ultimate achievements in color enhancement by HPHT-annealing?
Cape series diamond becoming colorless and brown resp. gray diamond adopting other colors than colorless, pink or blue.
The Gubelin Gem Lab engaged in a new study of HPHT-annealed specimens in order to elaborate criteria for the separation of the fancy diamond colors produced by the General Electric Company from the natural pink and blue colors. The key characteristics of the natural colors are briefly outlined and first indicators for HPHT treatment detection are given below.
Natural pink colors exist in both type Ia and type IIa diamond but exhibit a wider color variety in the first group. Type Ia diamond is found in pure pink to red to purple hues but pink and red are more frequently combined with orange and brown color modifiers. Type IIa diamond is limited to light pink to pink hues which may be modified by secondary orange or brown colors. Red hues do not occur in this group but purple does, as a rare and subordinate modifier at least.
In our natural pink study group of over 100 gem quality diamonds, 75% belonged to type Ia, 2% to the mixed type IbIaA, and 22% to type IIa (of which 15% revealed nitrogen-free infrared survey spectra, whereas 7% showed trace amounts of nitrogen as A or B aggregates or as single nitrogen).
In pink type Ia diamond in particular, an irregular color lamination and patchiness can frequently be observed under magnification. These obvious disturbances are plausibly interpreted as being caused by internal plastic deformation which itself is a reaction of the diamond structure to the impact of geotectonic shear stress (active during orogenetic phases), thus avoiding breakage. However, the cause for the pink color center, a wideband absorption centered at 560nm (2.2 eV), is not known in detail.
The strength of the 560nm absorption band determines the intensity of the type Ia pink color. Pink changes to red or purple when this band reaches higher amplitudes (with absorption coefficients in the order of 0.6 cm¯¹ and above). Nitrogen contents in the form of A and/or B aggregates vary in natural pink diamond from extremely small (in type IIa) to extremely large. In type Ia diamond, hydrogen may be present as well, however, in minor to moderate amounts only. Type IIa diamond features the same 560 nm absorption system and an identical but limited intensity relationship (mentioned above). It follows that neither nitrogen nor hydrogen impurities cause the pink color.
In pink diamond, a slight increase of the general absorption in the blue to violet regions of the spectrum results in an orange color modifier which in turn may alter to a brown modifier when the underlying absorption rises more strongly. This absorption is caused by another, equally unknown type of structural defect in the diamond crystal lattice.
In addition to the above color centers, N3 and H3 absorption in type Ia diamond may add a yellowish to orangy modifier component when present in some strength. This combination is typically encountered in Argyle and Brazilian brownish to purplish pink and red diamond. A rarely occurring 480nm absorption band adds a pure orange component to pink diamond colors.
Natural blue diamond varies less than in hue than pink color group. The only modifier of importance is gray. Natural blue occurs in type IIb diamond exclusively (rare specimens being gray violet rather than blue and belonging to hydrogen-rich type IaB). Type IIb diamond is an electric semiconductor due to the substitution of carbon atoms by ppb amounts of boron on the lattice sites of diamond.
The absorption diagram of blue diamond is characterized by a unique mid-infrared absorption superimposed n the inherent diamond absorption in the two-phonon region, with lesser absorption in the adjacent one and three phonon areas. The strongest absorption band is situated at 2802 wavenumbers. It is also typical for blue diamond that the absorption level steadily decreases from the mid-infrared through the near-infrared and visible regions into the ultraviolet part of the electromagnetic spectrum without showing any absorption bands. The absorption minima of blue diamonds fluctuate from 240nm at the base of the fundamental absorption edge to about 500nm. This variation does have an influence on the exact hue of the blue colors which may range from violetish to slightly greenish blue. The dominant wavelengths, as determined by colorimetric measurement, lie in the 465 to 495nm region and confirm that the primary hue is blue. Only one specimen was encountered so far with a dominant wavelength of 435nm corresponding to a violet-blue hue.
The hues of type IIb diamonds frequently are not easy to determine visually due to their weak color saturations and relatively high tones. The type IIb infrared absorption, e.g. the 2802 wn band, could serve as an indicator for the saturation of blue since it is related to the boron content. However, the absorption coefficient of this and other MIR absorption bands for some reason does not appear to be straightforward measure of the blue saturation of type IIb diamond. When the general absorption in type IIb diamond rises to higher levels, and this is particularly important in the visible part of the spectrum, the color impression shifts to bluish gray and even to neutral gray colors (44% of the blue group of 75 specimens grade blue, 40% mixed blue to gray, 8% neutral gray and 1% violet blue).
There is a small proportion (7%) of type IIb diamonds which possesses an increased absorption in the entire ultraviolet region. Accordingly their absorption minimum is more pronounced than in the pure blue colors and shifts into the center of the visible region, with dominant wavelengths ranging from about 500 to slightly over 600nm. Such diamonds essentially appear gray with a greenish to yellowish color modifier. It is interesting to note that greenish gray and yellowish gray colors also occur in type Ia diamond, showing high B nitrogen aggregate and high hydrogen contents, respectively high A aggregate and H contents.
The presence of gray color modifier in type IIb blue diamond may be interpreted as a color generated by the combination of boron with single nitrogen or other chemical impurities and/or by structural defects. However, gray color may also be independent of boron traces at all. A very weak 270 nm band was encountered in several natural blue diamonds and is allocated to single nitrogen.
HPHT Pink and Blue
Prior to 1999, it may have appeared inconceivable that natural off-color diamonds could be improved to obtain the best colors known (D to H color grades), i.e. colorlessness. However, the General Electric Company successfully achieved this breakthrough by applying a modified version of the high pressure/high temperature technology used to grow synthetic diamonds. Since the turn of the millennium, GE has been marketing these virtually colorless diamonds predominantly on the American market and under the brand name, Bellataire (formerly GE POL).
Fancy pink and blue diamond colors are described ad desirable as the white ones. As a consequence, the production of pink and blue became the second great challenge and in 2000. GE managed to add convincing pink and blue color replicas to the wide range of already existing treated diamond colors. In contrast to those irradiated and annealed pink to purple and irradiated blue to green diamond colors, General Electric’s latest products look entirely natural. The exact starting material and its abundance will not be made public by GE. However, experience gained in our study of GE POL diamonds before and after HPHT-annealing (Smith et. al 2000) tells us that the potentially improvable diamond rough must be restricted to type IIa brown respectively type IIB gray to brown specimens of fairly high clarity grades. This implies that the number of diamonds HPHT-annealable to pink and blue colors is considerably inferior to that of the colorless type IIa specimens and that most of the enhanced fancy colors may be low in intensity. A preliminary sampling consisted of six (0.14 to 8.55 ct) pink and two (0.21 and 0.27 ct) blue diamonds HPHT-annealed by GE. The pink stones investigated evidenced that only type IIa and near-type IIa diamonds had been selected. Colorimetric data showed that the resulting pink and blue hues are well within the range of their natural type IIa resp. IIb counterparts. Red or strong blue colors were not observed in this batch, but it included light to intense pink to purple pink colors plus one faint blue and one medium blue specimen each. Brown resp. gray modifiers were subordinate. At this moment, it is safe to state that, comparable to colorless Bellataire diamonds, gemological standard methods (microscopy, UV fluorescence etc.) will not permit a safe separation of natural and HPHT-annealed type IIa pink and semi-conductive blue diamonds. The mid-infrared and UV/VIS spectra of five (out of six) pink samples revealed nitrogen (A or B aggregates, N3 and N9 centers), however, in trace amounts only. The spectra of the blue specimens were very similar to those of the natural colors as well.
Among the optical techniques, Raman photo-luminescence with He/Cd and an Arion laser offer the most promising results. The color enhanced diamonds showed a smaller number of PL bands than recorded for natural colors and the intensities of the bands also differed noticeably. As an example, the 575nm and 637nm bands of the Nº and N centers respectively were definitely stronger than in natural pink diamonds. More and improved criteria are to be expected for both color groups from a larger data base. Advanced testing methods such as X-ray topography or cathodoluminescence applied during our former investigation of eleven colorless diamonds before and after HPHT processing by GE were not used for reasons of limited time and absence of diamonds selected to be processed.
What can be expected as the ultimate achievements in color enhancement by HPHT-annealing?
Cape series diamond becoming colorless and brown resp. gray diamond adopting other colors than colorless, pink or blue.
The Five Ages Of A Lecturer
(via Wahroongai News, Volume 31, Number 3, March 1997)
In How Professors Develop as Teachers, Peter Kugel (TLDU Talk, Issue No.3, July 1996—Teaching and Learning Development Unit, University of Waikato quoting Peter Kugel’s (1993) How Professors Develop as teachers, studies in Higher Education) suggests five distinct stages in the development of a teacher in higher education, and the transitions between each of these stages.
Stage 1: Focus on self
At the start of their teaching career, Kugel suggests, lecturers are mainly concerned with themselves, and more specifically with their survival in front of their first few classes.
Transition 1—self to subject. Once they know they can survive, and even start to feel good about their teachings, their focus shifts rapidly to the subject matter.
Stage 2: Focus on subject
Here the lecturer rediscovers their enthusiasm for their subject, and works hard to extend their knowledge further and then to share it all with their students.
Transition 2—subject to student. After a while, the lecturer may start to notice that students are not learning all that the lecturer is teaching, and may not all share the lecturer’s enthusiasm. Why might this be?
Stage 3: Focus on student
The lecturer sees how greatly students differ one another—in approach to learning, in interest, in motivation, in competence. The lecturer starts to adopt a wider variety of approaches to engage the heterogeneous body of students before them. The lecturer’s interest shift from ‘what am I saying?’ to ‘what are they hearing?’
Transition 3—students as receiver to student as active learner. Even when focusing on the students, the lecturer was still concentrating on what she or he was doing to the students rather than on what the students were doing. The lecturer is now finding limits to what this can achieve.
Stage 4: Focus on student learning
The lecturer increasingly devises appropriate student activities and opportunities for learning.
Transition 4—student as active learner to student as independent learner. The more actively the students engage with their work, the more responsibility they take for their own and each other’s learning.
Stage 5: Focus on the student as an independent learner
When the student truly knows how to learn for her or himself, the lecturer’s work with that student is successfully complete.
In How Professors Develop as Teachers, Peter Kugel (TLDU Talk, Issue No.3, July 1996—Teaching and Learning Development Unit, University of Waikato quoting Peter Kugel’s (1993) How Professors Develop as teachers, studies in Higher Education) suggests five distinct stages in the development of a teacher in higher education, and the transitions between each of these stages.
Stage 1: Focus on self
At the start of their teaching career, Kugel suggests, lecturers are mainly concerned with themselves, and more specifically with their survival in front of their first few classes.
Transition 1—self to subject. Once they know they can survive, and even start to feel good about their teachings, their focus shifts rapidly to the subject matter.
Stage 2: Focus on subject
Here the lecturer rediscovers their enthusiasm for their subject, and works hard to extend their knowledge further and then to share it all with their students.
Transition 2—subject to student. After a while, the lecturer may start to notice that students are not learning all that the lecturer is teaching, and may not all share the lecturer’s enthusiasm. Why might this be?
Stage 3: Focus on student
The lecturer sees how greatly students differ one another—in approach to learning, in interest, in motivation, in competence. The lecturer starts to adopt a wider variety of approaches to engage the heterogeneous body of students before them. The lecturer’s interest shift from ‘what am I saying?’ to ‘what are they hearing?’
Transition 3—students as receiver to student as active learner. Even when focusing on the students, the lecturer was still concentrating on what she or he was doing to the students rather than on what the students were doing. The lecturer is now finding limits to what this can achieve.
Stage 4: Focus on student learning
The lecturer increasingly devises appropriate student activities and opportunities for learning.
Transition 4—student as active learner to student as independent learner. The more actively the students engage with their work, the more responsibility they take for their own and each other’s learning.
Stage 5: Focus on the student as an independent learner
When the student truly knows how to learn for her or himself, the lecturer’s work with that student is successfully complete.
Body Jewellery
By Donald Willcox
Sir Isaac Pitman and Sons Ltd
1974 ISBN 0-273-00723-8
Sir Isaac Pitman and Sons writes:
Essentially a pictorial survey of the best in international jewellery design today, Body Jewellery is made up of essays by those designers who have contributed pieces of work to the photographic section.
The designers range from the world famous to less well-known but successful beginners. Donald Willcox provides the summarizing introduction. A variety of topics are covered: from technical aspects of jewellery work to general views on the way jewellery design is developing or ought to develop. The writers all share a determination to break away from the confining tradition of gold and silver jewellery for the ears, wrist, neck and fingers, and to incorporate instead more of the artist’s imagination in ornaments for virtually any part of the body, made out of more or less any malleable material.
Jewellery craftsmen will find ideas and encouragement here. With over 400 illustrations, it is a valuable book for art students and a useful reference for designers.
Donald Willcox describes himself as an ‘author, lunatic, poet, craftsmen, critic and educator..’. He is the author of three poetry books and many on design and crafts, including Leather, which is also published by Pitman. His articles have been widely published in such magazines as Craft Horizons and American Artist.
Sir Isaac Pitman and Sons Ltd
1974 ISBN 0-273-00723-8
Sir Isaac Pitman and Sons writes:
Essentially a pictorial survey of the best in international jewellery design today, Body Jewellery is made up of essays by those designers who have contributed pieces of work to the photographic section.
The designers range from the world famous to less well-known but successful beginners. Donald Willcox provides the summarizing introduction. A variety of topics are covered: from technical aspects of jewellery work to general views on the way jewellery design is developing or ought to develop. The writers all share a determination to break away from the confining tradition of gold and silver jewellery for the ears, wrist, neck and fingers, and to incorporate instead more of the artist’s imagination in ornaments for virtually any part of the body, made out of more or less any malleable material.
Jewellery craftsmen will find ideas and encouragement here. With over 400 illustrations, it is a valuable book for art students and a useful reference for designers.
Donald Willcox describes himself as an ‘author, lunatic, poet, craftsmen, critic and educator..’. He is the author of three poetry books and many on design and crafts, including Leather, which is also published by Pitman. His articles have been widely published in such magazines as Craft Horizons and American Artist.
Wednesday, March 28, 2007
Synthetic Corundum
(via Wahroongai News, Volume 23, Number 2, February 1989)
The natural growth angle (angle to the c-axis on which the atoms of Al2O3 will stack) of the Verneuil corundum boule is 60°.
Boules grown on seeds cut at 90° to the c-axis have square cross sections.
Boules grown on seeds cut at 0° to the c-axis fracture readily…..both during growth, and during cooling or subsequent cutting.
It is not possible to cut or shape any Verneuil corundum boules until they have been adequately annealed to remove stresses induced during their growth.
Impurities of materials, bubbles, included unmelted powder particles, poor dissemination of the chromophore, and an unclean vertical blowtorch—all contribute to the production of poor quality boules.
The natural growth angle (angle to the c-axis on which the atoms of Al2O3 will stack) of the Verneuil corundum boule is 60°.
Boules grown on seeds cut at 90° to the c-axis have square cross sections.
Boules grown on seeds cut at 0° to the c-axis fracture readily…..both during growth, and during cooling or subsequent cutting.
It is not possible to cut or shape any Verneuil corundum boules until they have been adequately annealed to remove stresses induced during their growth.
Impurities of materials, bubbles, included unmelted powder particles, poor dissemination of the chromophore, and an unclean vertical blowtorch—all contribute to the production of poor quality boules.
The Lost Weekend
Memorable quote (s) from the movie:
Don Birnam (Ray Milland): It shrinks my liver, doesn't it, Nat? It pickles my kidneys, yeah. But what it does to the mind? It tosses the sandbags overboard so the balloon can soar. Suddenly I'm above the ordinary. I'm competent. I'm walking a tightrope over Niagara Falls. I'm one of the great ones. I'm Michaelangelo, molding the beard of Moses. I'm Van Gogh painting pure sunlight. I'm Horowitz, playing the Emperor Concerto. I'm John Barrymore before movies got him by the throat. I'm Jesse James and his two brothers, all three of them. I'm W. Shakespeare. And out there it's not Third Avenue any longer, it's the Nile. Nat, it's the Nile and down it moves the barge of Cleopatra.
Don Birnam (Ray Milland): It shrinks my liver, doesn't it, Nat? It pickles my kidneys, yeah. But what it does to the mind? It tosses the sandbags overboard so the balloon can soar. Suddenly I'm above the ordinary. I'm competent. I'm walking a tightrope over Niagara Falls. I'm one of the great ones. I'm Michaelangelo, molding the beard of Moses. I'm Van Gogh painting pure sunlight. I'm Horowitz, playing the Emperor Concerto. I'm John Barrymore before movies got him by the throat. I'm Jesse James and his two brothers, all three of them. I'm W. Shakespeare. And out there it's not Third Avenue any longer, it's the Nile. Nat, it's the Nile and down it moves the barge of Cleopatra.
(New) Russian Tanzanite Imitation
Jewellery News Asia (August, 1999) writes:
A visually effective tanzanite imitation of Russian manufacture has entered the marketplace. This imitation is potentially confusing as it displays greenish blue to purplish pink directional pleochroism. Investigations by Shane McClure of GIA’s Gem Trade Lab in New York have revealed that this imitation is a synthetic forsterite (magnesium silicate)…..the magnesian end member of the forsterite-fayalite solid solution series of which the gemstone peridot is an intermediate member.
According to McClure the presence of scattered ‘pinpoints’ and small ‘needles’ suggest that this man-made material has been synthesized by the crystal pulling (Czochralski) technique. This imitation which is doped by cobalt, and therefore should display Co absorption spectrum and fluoresces red under LWUV and the Chelsea filter; specific gravity is 3.42 and refractive index is 1.635-1.670.
A visually effective tanzanite imitation of Russian manufacture has entered the marketplace. This imitation is potentially confusing as it displays greenish blue to purplish pink directional pleochroism. Investigations by Shane McClure of GIA’s Gem Trade Lab in New York have revealed that this imitation is a synthetic forsterite (magnesium silicate)…..the magnesian end member of the forsterite-fayalite solid solution series of which the gemstone peridot is an intermediate member.
According to McClure the presence of scattered ‘pinpoints’ and small ‘needles’ suggest that this man-made material has been synthesized by the crystal pulling (Czochralski) technique. This imitation which is doped by cobalt, and therefore should display Co absorption spectrum and fluoresces red under LWUV and the Chelsea filter; specific gravity is 3.42 and refractive index is 1.635-1.670.
American Freshwater Pearls
(via Wahroongai News, Volume 33, No.8, August 1999)
The freshwater mussels of the rivers and lakes of North America produce a surprising range of both natural and cultural pearls.
Natural pearls
North American Indians, who lived along the rivers and lakes of North America, made use of indigenous freshwater mussels both as a source of food and as a valued source of pearls for ornamental purposes. By the mid 16th century Spanish explorers also had become aware of and greatly appreciated this source of natural pearls.
Following the mid-19th century discovery of pearls in Notch Brook near Paterson, New Jersey, an active trade in these pearls and their shells began in North America. This trade exploded some decades later as pearl shelling also developed along the rivers of Ohio, Wisconsin, Tennessee, and Arkansas. By the end of World War II these fisheries were no longer economically viable, as plastic has supplanted pearl shell for the manufacture of buttons. The pearl shelling industry of North America revived during the early 1950, when Japanese demand for shells for the manufacture of bead nuclei suitable implanting into Akoya oysters became paramount. Today, natural pearls are still recovered from these rivers and lakes; but only as a by-product of the pearl shelling industry.
Many species of bivalve freshwater mollusk, belonging to the family Unionidae, inhabit the sandy-gravely bottoms of fast flowing rivers, and to a lesser extent the more muddy bottoms of gravely lakes of the Mississippi and its tributaries. However, over the last century damming these rivers, increased silting from agriculture and strip mining, and the introduction of competitive predators such the zebra mussel have decimated the native mussel population of North America. Today hardy survivors such as the pigtoe (Pleerobema cordatum) maple leaf (Quadrula quadrula), three ridge (Amblema costata), and washboard (Megiaonaias gigantean) are still surviving with some difficulty.
Natural pearl form as a result of small pieces of mantle tissue dislodged from mussels by the bites of predatory fish, by invasion of the mussel’s body tissues by boring parasites, or by the accidental implantation of fragments of shell or fish scales into mantle tissues. The shape of pearls obtained from these freshwater mussels varies with where they grow within the mussel. For example, round pearls form in or around the posterior adductor muscle, adjacent beak area, or the body of the mollusk. It is hypothesized that the opening and closing of valves of the mussel rotates the forming pearl thus producing an even distribution of nacre. Elongated symmetrical shapes of pearl form between the adductor muscle and the hinge: with ridged barrels probably resulting from the forming pearl rotating against a projection from the hinge. Button shaped pearls and turtle backs (with flattish bottoms) are found near the outer lips of the valves. Flattish teardrop shaped ‘wings’ form in the posterior hinge area, while more angular chunky pearls form in the anterior hinge area. Rare bumpy rosebud pearls either form in the beak area or deep within the body of the mussel. Colors of natural pearls range from common white to attractive pastel shades of pink, rose, lavender and purple. The lusters of these pearls vary widely. Major factors controlling the color and luster of these freshwater pearls include the distribution of color across the shell of various species of mussel, location of the pearl in the mussel, the health of the mussel, and water and environmental conditions under which the pearl grew.
Cultured pearls
In the early 1960s the Tennessee Shell Company—the major supplier of freshwater shell for the manufacture of beads for the Japanese Akoya industry—began experiments in the culture of freshwater pearls in a man-made TVA lake near Lexington, Tennessee. These experiments were initiated by John Latendresse and his Japanese-born wife. Twenty years later and with the assistance of available Japanese freshwater pearl cultivating technology, pearl culture farms had been set up and were operating economically in several unpolluted lakes leased from TVA.
American cultured pearls are produced in the following sequence, based on basic Lake Biwa technology:
- Individual hookah-equipped divers collect mature mother mussels from the Mississippi River and its tributaries; care being taken that younger mussels are left to continue breeding.
- The harvested mussels are placed into pockets of ‘kangaroo’ nets that hold up to 18 shells. Shells are then transported to the pearl farm where, following inspection and sorting, the mussels are suspended vertically from rafts made from sealed polythene pipes that are so arranged as to leave sufficient space between both mussels and nets to allow the bivalves to recuperate (for at least a month) to feed, to grow, and indeed to spawn. ‘Mother shells’ are kept separated from ‘sacrifice’ mussels.
- Nucleation occurs at the farm using American-trained technologists and American implant technology based in traditional Japanese methods. Once cleaned, the ‘mother shells’ are held in troughs located in the implant lab.
- Because of their large size American freshwater mussels are multi-nucleated using MOP beads of various shapes.
- Three types of pearls are produced: hemispherical blister pearls, bead nucleated whole pearls of various shapes, keshis.
- Following recuperation under the controlled conditions of laboratory-based ‘ponds’, the implanted mussels are returned to the pearl farm for periods ranging from 1½ (for blister pears) to 3-5 years (for whole pearls) depending on the nature of the implant.
- For blister pearls the shells are first cleaned, their cultured blister pearls sawn from the shell, and the sawn edges shaped and polished either to free from or calibrated sizes.
- Fancy shape free pearls, cultivated in the body of the mussel, are covered by killing the mussel at harvest. Due to shaped nuclei these pearls are available in a range of interesting shapes that include marquise, teardrop, bar, marquise, disc, triangle etc.,--with and without bumps, circles, and nodelles (fish-tails).
- Factors determining the grade of these pearls include their luster, orient, color, shape and color.
- Over the years mortality rates for American freshwater cultured pearls have been reduced to less than 5%.
The freshwater mussels of the rivers and lakes of North America produce a surprising range of both natural and cultural pearls.
Natural pearls
North American Indians, who lived along the rivers and lakes of North America, made use of indigenous freshwater mussels both as a source of food and as a valued source of pearls for ornamental purposes. By the mid 16th century Spanish explorers also had become aware of and greatly appreciated this source of natural pearls.
Following the mid-19th century discovery of pearls in Notch Brook near Paterson, New Jersey, an active trade in these pearls and their shells began in North America. This trade exploded some decades later as pearl shelling also developed along the rivers of Ohio, Wisconsin, Tennessee, and Arkansas. By the end of World War II these fisheries were no longer economically viable, as plastic has supplanted pearl shell for the manufacture of buttons. The pearl shelling industry of North America revived during the early 1950, when Japanese demand for shells for the manufacture of bead nuclei suitable implanting into Akoya oysters became paramount. Today, natural pearls are still recovered from these rivers and lakes; but only as a by-product of the pearl shelling industry.
Many species of bivalve freshwater mollusk, belonging to the family Unionidae, inhabit the sandy-gravely bottoms of fast flowing rivers, and to a lesser extent the more muddy bottoms of gravely lakes of the Mississippi and its tributaries. However, over the last century damming these rivers, increased silting from agriculture and strip mining, and the introduction of competitive predators such the zebra mussel have decimated the native mussel population of North America. Today hardy survivors such as the pigtoe (Pleerobema cordatum) maple leaf (Quadrula quadrula), three ridge (Amblema costata), and washboard (Megiaonaias gigantean) are still surviving with some difficulty.
Natural pearl form as a result of small pieces of mantle tissue dislodged from mussels by the bites of predatory fish, by invasion of the mussel’s body tissues by boring parasites, or by the accidental implantation of fragments of shell or fish scales into mantle tissues. The shape of pearls obtained from these freshwater mussels varies with where they grow within the mussel. For example, round pearls form in or around the posterior adductor muscle, adjacent beak area, or the body of the mollusk. It is hypothesized that the opening and closing of valves of the mussel rotates the forming pearl thus producing an even distribution of nacre. Elongated symmetrical shapes of pearl form between the adductor muscle and the hinge: with ridged barrels probably resulting from the forming pearl rotating against a projection from the hinge. Button shaped pearls and turtle backs (with flattish bottoms) are found near the outer lips of the valves. Flattish teardrop shaped ‘wings’ form in the posterior hinge area, while more angular chunky pearls form in the anterior hinge area. Rare bumpy rosebud pearls either form in the beak area or deep within the body of the mussel. Colors of natural pearls range from common white to attractive pastel shades of pink, rose, lavender and purple. The lusters of these pearls vary widely. Major factors controlling the color and luster of these freshwater pearls include the distribution of color across the shell of various species of mussel, location of the pearl in the mussel, the health of the mussel, and water and environmental conditions under which the pearl grew.
Cultured pearls
In the early 1960s the Tennessee Shell Company—the major supplier of freshwater shell for the manufacture of beads for the Japanese Akoya industry—began experiments in the culture of freshwater pearls in a man-made TVA lake near Lexington, Tennessee. These experiments were initiated by John Latendresse and his Japanese-born wife. Twenty years later and with the assistance of available Japanese freshwater pearl cultivating technology, pearl culture farms had been set up and were operating economically in several unpolluted lakes leased from TVA.
American cultured pearls are produced in the following sequence, based on basic Lake Biwa technology:
- Individual hookah-equipped divers collect mature mother mussels from the Mississippi River and its tributaries; care being taken that younger mussels are left to continue breeding.
- The harvested mussels are placed into pockets of ‘kangaroo’ nets that hold up to 18 shells. Shells are then transported to the pearl farm where, following inspection and sorting, the mussels are suspended vertically from rafts made from sealed polythene pipes that are so arranged as to leave sufficient space between both mussels and nets to allow the bivalves to recuperate (for at least a month) to feed, to grow, and indeed to spawn. ‘Mother shells’ are kept separated from ‘sacrifice’ mussels.
- Nucleation occurs at the farm using American-trained technologists and American implant technology based in traditional Japanese methods. Once cleaned, the ‘mother shells’ are held in troughs located in the implant lab.
- Because of their large size American freshwater mussels are multi-nucleated using MOP beads of various shapes.
- Three types of pearls are produced: hemispherical blister pearls, bead nucleated whole pearls of various shapes, keshis.
- Following recuperation under the controlled conditions of laboratory-based ‘ponds’, the implanted mussels are returned to the pearl farm for periods ranging from 1½ (for blister pears) to 3-5 years (for whole pearls) depending on the nature of the implant.
- For blister pearls the shells are first cleaned, their cultured blister pearls sawn from the shell, and the sawn edges shaped and polished either to free from or calibrated sizes.
- Fancy shape free pearls, cultivated in the body of the mussel, are covered by killing the mussel at harvest. Due to shaped nuclei these pearls are available in a range of interesting shapes that include marquise, teardrop, bar, marquise, disc, triangle etc.,--with and without bumps, circles, and nodelles (fish-tails).
- Factors determining the grade of these pearls include their luster, orient, color, shape and color.
- Over the years mortality rates for American freshwater cultured pearls have been reduced to less than 5%.
Nineteenth Century Jewellery
By Peter Hinks
Faber and Faber Ltd
1975 ISBN 0-571-10650-1
Faber and Faber writes:
More jewellery was made in Europe during the nineteenth century than in any other period before or since. What is more, the jewellery was extremely varied—the predilections, obsessions and changing circumstances of England, France, Italy and Germany, for example, being faithfully reflected in their pieces—and much was of the highest quality. The discovery of diamonds in South Africa, the gold rush in the States and Australia, the theatre, war, archaeology, the latest ‘Novelty’, all were sources of inspiration for the jeweler. Nineteenth Century Jewellery both describes in absorbing detail the beautiful and sometimes bizarre ornaments of an extraordinary era and tells us much of the craftsmen who made them and the people through whose hands they passed: women of taste and fashion, shopmen, peddlers, confidence tricksters. It is probably the first book on the subject to cove the whole of Europe comprehensively.
The Revolutionary, Napoleonic, post Napoleonic, mid-century, Second Empire, High Victorian and Fin de Siecle styles of jewellery are all pinpointed and analyzed. And there are also useful chapters on the Arts and Crafts Movement, on Art Nouveau, peasant and mourning jewellery and on collecting, and an appendix of the gold and silver marks of ten countries. The development of the great centers of manufacture both in Europe and America is clearly traced. The selection of pieces illustrated is unusual and arresting.
Peter Hinks is Sotheby’s leading expert on nineteenth century jewellery.
Faber and Faber Ltd
1975 ISBN 0-571-10650-1
Faber and Faber writes:
More jewellery was made in Europe during the nineteenth century than in any other period before or since. What is more, the jewellery was extremely varied—the predilections, obsessions and changing circumstances of England, France, Italy and Germany, for example, being faithfully reflected in their pieces—and much was of the highest quality. The discovery of diamonds in South Africa, the gold rush in the States and Australia, the theatre, war, archaeology, the latest ‘Novelty’, all were sources of inspiration for the jeweler. Nineteenth Century Jewellery both describes in absorbing detail the beautiful and sometimes bizarre ornaments of an extraordinary era and tells us much of the craftsmen who made them and the people through whose hands they passed: women of taste and fashion, shopmen, peddlers, confidence tricksters. It is probably the first book on the subject to cove the whole of Europe comprehensively.
The Revolutionary, Napoleonic, post Napoleonic, mid-century, Second Empire, High Victorian and Fin de Siecle styles of jewellery are all pinpointed and analyzed. And there are also useful chapters on the Arts and Crafts Movement, on Art Nouveau, peasant and mourning jewellery and on collecting, and an appendix of the gold and silver marks of ten countries. The development of the great centers of manufacture both in Europe and America is clearly traced. The selection of pieces illustrated is unusual and arresting.
Peter Hinks is Sotheby’s leading expert on nineteenth century jewellery.
Tuesday, March 27, 2007
Black Opal
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.
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.
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.
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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