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.
Friday, March 30, 2007
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.
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