Federico Pezzotta is an expert on Madagascar, and pezzottaite is named after him. The author also provides the geological landscape + the unique particularities of the gem deposits in Madagascar. Many experts believe Madagascar is vast with poor infrastructure + a virgin territory + there may be more surprises from from this island. Keep in touch.
Federico Pezzotta (Natural History Museum, Milan, Italy) writes:
Madagascar is host to an abundance and variety of gem materials as a result of its long and complex geologic history. The upper Archean to Neoproterozoic crystalline basement of Madagascar experienced locally unusual and even unique geologic conditions during several mountain-building events. Erosion of these rocks occurred during the late to post-tectonic uplift of the basement, and deposited Permian-Mesozoic sediments along the western margin of the Mozambique basin, locally forming immense paleoplacer deposits (e.g Ilakaka). More recently, the morphologic and climatic conditions of the island during the past few million years resulted in the formation of abundant secondary residual and alluvial gem deposits.
Even though research and mining of Madagascar’s gems has continued for more than a century, many large areas in the island remain poorly explored and have significant potential for the discovery of new deposits. Within the last few years, the country’s improved political situation has allowed for important developments in the scientific research, mining, and trading of gems.
Recently, two major discoveries occurred in Madagascar, both in Fianarantosa Province: (1) a series of multicolored tourmaline deposits, of both primary and residual nature, in a large area between the villages of Ambatofitorahana and Ambohimasoa, along the national road connecting the towns of Ambositra and Fianarantosoa; and (2) a multicolored sapphire deposit of residual nature located 17km south of the village of Ranotsara, southeast of the town of Ihosy.
The tourmaline deposits are related to a large rare-element miarolitic pegmatite field, surprisingly rather undocumented in the available geologic maps, that extends in a northeast-southwest direction for a distance of ~40km. Initial discoveries of tourmaline in the area were made in 1995-1996 with the mining of the primary and secondary residual deposits of Valozoro, a few kilometers southeast of Ambatofitorahana. No additional significant discoveries were made until August-September 2005 when, in the Anjoma area (located a few kilometers southwest of Ambatofitorahana), an enormous quantity of multicolored tourmaline (weighing several tones, but mainly of carving quality) was found close to the surface at Anjomanandihizna (also known as Nandihizana). Soon afterward, additional multicolored tourmaline deposits were discovered south of this area; the most important ones at Fiadanana (a few kilometers south of Valozoro), Ankitsikitsika (about 15 km south of Anjomanandihizana), and Antsengy (northwest of the village of Ambohimahasoa). Local gem dealers refer to this entire area as Camp Robin, from the name of a village in center of the district in which much of the gem trading occurs.
The new sapphire deposit, named Marosely, was discovered in October 2005. Transparent bipyramidal sapphire crystals, with colors ranging from blue to purple and, rarely, purplish red (ruby), have been recovered mainly in small size (less than 0.4 g). Larger crystals of gem quality are rare, but occasionally they exceed 2 g and produce good size cut stones. These crystals originated from the high grade metamorphic bedrock, and were concentrated in near-surface residual deposits through erosion. The total production of sapphire rough from Marosely, through June 2006 is estimated at about 500 kg.
Sunday, June 10, 2007
Saturday, June 09, 2007
More On The Black Swan Concept
(via Emergic) The Guardian wrote about Nassim Taleb’s “The BlackSwan”.
“If you are aware of your own ignorance, though, you can use it to make money, as Taleb did on Wall Street, as an options trader. Options are gambles about what the market will do. To sell an option to somebody else, you need to be confident you have some kind of theory about what will happen in the future. If you're right, you make a small amount of money; if you're wrong, you lose lots. Taleb, however, realized he had no theories. So he exploited everyone else's confidence, buying options according to no particular prediction. Most days, his rivals made a small amount of money, and he lost a small amount. But the one thing he could predict was that, if he waited long enough, something unpredictable would happen. When it did, some of his rivals would lose millions, and Taleb would make millions. It happened often enough for him to turn a big profit. It takes a rebellious nature, and an iron stomach, to go against the flow for so long. It is, perhaps, the kind of mindset that comes naturally to someone who lived through the Lebanese civil war - a classic, unpredictable black swan - and then found himself living as an exile, at one remove from American society. We are not all so good at resisting the herd's way of thinking.”
Bloomberg wrote:
There's an investment strategy to profit from improbability. “Be as hyper-conservative and hyper-aggressive as you can instead of being mildly aggressive or conservative,'' Taleb advises. “Instead of having medium risk, you have high risk on one side and no risk on the other. The average will be medium risk but constitutes a positive exposure to the Black Swan.''
The hand can feed the turkey for 1,000 days until, on day 1,001; it wrings the fowl's neck for Thanksgiving. The trick is to be the butcher, not the turkey.
“A thousand days cannot prove you right, but one day can prove you to be wrong,'' writes Taleb. “I am not urging you to stop being a fool. Just be a fool in the right places.''
With risk measures at or near record lows, including volatility indexes, corporate bond defaults, credit spreads and emerging-market yields, Taleb might help you dodge the next Black Swan.
Business Week wrote:
The Black Swan is not as unprecedented as Taleb claims. You may have encountered pieces of his arguments in recent popular books by the likes of Chris Anderson, James Gleick, Paul Ormerod, Duncan Watts, Steven Strogatz, Aaron Brown, and one of Taleb's few living heroes, Benoit Mandelbrot.
Moreover, despite Taleb's best efforts to make The Black Swan a useful guide to life, we human beings aren't wired to cope well with radical uncertainty. Donald Rumsfeld, the former Defense Secretary, famously cogitated in front of the microphones about "unknown unknowns," which is precisely Taleb's concept—and look where the philosophizing got him. Still, The Black Swan is a richly enjoyable read with an important message.
Nassim Taleb’s “The Black Swan” is one of the best and most important books you will read. Go get it!
“If you are aware of your own ignorance, though, you can use it to make money, as Taleb did on Wall Street, as an options trader. Options are gambles about what the market will do. To sell an option to somebody else, you need to be confident you have some kind of theory about what will happen in the future. If you're right, you make a small amount of money; if you're wrong, you lose lots. Taleb, however, realized he had no theories. So he exploited everyone else's confidence, buying options according to no particular prediction. Most days, his rivals made a small amount of money, and he lost a small amount. But the one thing he could predict was that, if he waited long enough, something unpredictable would happen. When it did, some of his rivals would lose millions, and Taleb would make millions. It happened often enough for him to turn a big profit. It takes a rebellious nature, and an iron stomach, to go against the flow for so long. It is, perhaps, the kind of mindset that comes naturally to someone who lived through the Lebanese civil war - a classic, unpredictable black swan - and then found himself living as an exile, at one remove from American society. We are not all so good at resisting the herd's way of thinking.”
Bloomberg wrote:
There's an investment strategy to profit from improbability. “Be as hyper-conservative and hyper-aggressive as you can instead of being mildly aggressive or conservative,'' Taleb advises. “Instead of having medium risk, you have high risk on one side and no risk on the other. The average will be medium risk but constitutes a positive exposure to the Black Swan.''
The hand can feed the turkey for 1,000 days until, on day 1,001; it wrings the fowl's neck for Thanksgiving. The trick is to be the butcher, not the turkey.
“A thousand days cannot prove you right, but one day can prove you to be wrong,'' writes Taleb. “I am not urging you to stop being a fool. Just be a fool in the right places.''
With risk measures at or near record lows, including volatility indexes, corporate bond defaults, credit spreads and emerging-market yields, Taleb might help you dodge the next Black Swan.
Business Week wrote:
The Black Swan is not as unprecedented as Taleb claims. You may have encountered pieces of his arguments in recent popular books by the likes of Chris Anderson, James Gleick, Paul Ormerod, Duncan Watts, Steven Strogatz, Aaron Brown, and one of Taleb's few living heroes, Benoit Mandelbrot.
Moreover, despite Taleb's best efforts to make The Black Swan a useful guide to life, we human beings aren't wired to cope well with radical uncertainty. Donald Rumsfeld, the former Defense Secretary, famously cogitated in front of the microphones about "unknown unknowns," which is precisely Taleb's concept—and look where the philosophizing got him. Still, The Black Swan is a richly enjoyable read with an important message.
Nassim Taleb’s “The Black Swan” is one of the best and most important books you will read. Go get it!
World's Largest Available Natural Pearl To Be Auctioned
The 575 carat pearl from 12th century Mongolia was formerly owned by Chinese emperors, Persian kings, the grandson of Genghis Khan and Marco Polo. It will be up for bidding in Abu Dhabi's Emirates Palace and on the Internet, where it is estimated to raise up to US$8 million (EUR5.89 million). The real story (via AP) @ http://english.pravda.ru/news/society/02-05-2007/90823-largest_pearl-0
Prediction: DTC to send formal Sightholder Termination Notices to All 93 Clients
Chaim Even-Zohar writes about the status of new DTC (Diamond Trading Company) sightholders + existing contracts + the uncertainities @ http://www.idexonline.com/portal_FullEditorial.asp?TextSearch=&KeyMatch=0&id=27309
Geology Of Placer Gem Deposits
Here is an experts view on placer deposits and its commercial significance in gem producing countries around the world + the geological and gemological characteristics that are important in identifying the particularities of placer deposits.
James M Prudden (Prudden GeoScience Services, Nevada, USA) writes:
Placer gem depositional environments consist of colluvial, fluvial, and beach deposits. The weathering of primary gem-bearing deposits forms overlying eluvial deposits, and the down-slope migration of the residual gems by both gravity and water creates colluvial deposits. Fluvial systems range from youthful through mature and old-age sedimentological regimes with associated channel geometrics that determine the hydraulic energy and therefore the locations of gem deposition. Fluvial systems commence with straight steep-channel gradients, with low depth-to width ratios containing unsorted clasts and large gems. This evolves into to the downstream, low-energy, old-age fluvial systems with low channel gradients that host bedded, well-sorted smaller clasts deposited in a meandering fashion within a broad flood plane. Gems in this environment are smaller and more rounded. At the point where the river enters a marine or lacustrine environment, the resulting abrupt gradient change is very favorable for gem deposition. Wave energy and long shore currents further winnow and transport gems in beach environments. Alpine and continental glaciers are nature’s bulldozers and the braded fluvial streams that are fed from their melt water effectively concentrate the contained gems from the glacial rubble.
Gem characteristics such as specific gravity, hardness, shape and durability will influence their related depositional environments and survivability, thus favoring the economic concentrations of certain gems in the fluvial milling environment.
Select case histories of a variety of placer deposits illustrate the practicality of applying detailed geology and sedimentology to placer gem exploration:
1. Australian Tertiary modified paleo-colluvial type sapphire deposits, derived from the weathering of alkaline basalts, have been a major global source of sapphires.
2. Namibian long-shore diamond distribution along the Atlantic Ocean coast constitutes the world’s most valuable diamond deposit, extending westward 100km to the continental shelf edge and 200km northward. The diamonds were originally liberated from the South African kimberlites (and possibly more distant sources) by post-Gondawana erosion of the southern African craton, which commenced in the humid Middle Cretaceous with the formation of the ancient Karoo and Kalahari Rivers. Subsequent erosion of these diamondiferous placers was accomplished by the Orange River in the Miocene. Prolonged winnowing of the diamonds increased their value by about 500%.
3. Fluvial reworking of glacial sediments in British Colombia, Canada, concentrated sapphires and garnets from several cubic kilometers of glacial material.
4. A fluvial diamond deposit in China’s Hunan province was deposited on completely weathered karst bedrock, which presents challenges to sampling and mining.
James M Prudden (Prudden GeoScience Services, Nevada, USA) writes:
Placer gem depositional environments consist of colluvial, fluvial, and beach deposits. The weathering of primary gem-bearing deposits forms overlying eluvial deposits, and the down-slope migration of the residual gems by both gravity and water creates colluvial deposits. Fluvial systems range from youthful through mature and old-age sedimentological regimes with associated channel geometrics that determine the hydraulic energy and therefore the locations of gem deposition. Fluvial systems commence with straight steep-channel gradients, with low depth-to width ratios containing unsorted clasts and large gems. This evolves into to the downstream, low-energy, old-age fluvial systems with low channel gradients that host bedded, well-sorted smaller clasts deposited in a meandering fashion within a broad flood plane. Gems in this environment are smaller and more rounded. At the point where the river enters a marine or lacustrine environment, the resulting abrupt gradient change is very favorable for gem deposition. Wave energy and long shore currents further winnow and transport gems in beach environments. Alpine and continental glaciers are nature’s bulldozers and the braded fluvial streams that are fed from their melt water effectively concentrate the contained gems from the glacial rubble.
Gem characteristics such as specific gravity, hardness, shape and durability will influence their related depositional environments and survivability, thus favoring the economic concentrations of certain gems in the fluvial milling environment.
Select case histories of a variety of placer deposits illustrate the practicality of applying detailed geology and sedimentology to placer gem exploration:
1. Australian Tertiary modified paleo-colluvial type sapphire deposits, derived from the weathering of alkaline basalts, have been a major global source of sapphires.
2. Namibian long-shore diamond distribution along the Atlantic Ocean coast constitutes the world’s most valuable diamond deposit, extending westward 100km to the continental shelf edge and 200km northward. The diamonds were originally liberated from the South African kimberlites (and possibly more distant sources) by post-Gondawana erosion of the southern African craton, which commenced in the humid Middle Cretaceous with the formation of the ancient Karoo and Kalahari Rivers. Subsequent erosion of these diamondiferous placers was accomplished by the Orange River in the Miocene. Prolonged winnowing of the diamonds increased their value by about 500%.
3. Fluvial reworking of glacial sediments in British Colombia, Canada, concentrated sapphires and garnets from several cubic kilometers of glacial material.
4. A fluvial diamond deposit in China’s Hunan province was deposited on completely weathered karst bedrock, which presents challenges to sampling and mining.
Role Of Beryllium In The Coloration Of Fe and Cr-doped Synthetic Corundum
Thailand is perceived as one of the gemstone refineries of the world. The experts from GIT shares their opinion (s) on the pros and cons of beryllium treatment in natural and synthetic corundum.
Visut Pisutha Arnond, Tobias Hager, Pornsawat Wathankul, Wilawan Atichat, Jitrin Nattachai, Chakkaphant Sutthirat, and Bootawee Sriprasert writes:
X-radiation and Be-diffusion heating experiments were performed on an iron-doped (colorless) synthetic corundum and a chromium-doped (pink) synthetic corundum to evaluate the role of beryllium in causing color in the Be-Fe-Al2O3 and Be-Cr-Al2O3 systems.
The iron-doped corundum, containing around 140-170 ppm by weight of Fe with negligible concentrations of other trace elements, was irradiated with X-rays (60 kV, 53 mA) for 30 minutes, then the color was faded for one hour with a 100-watt light bulb, and finally the sample was heat treated in a crucible with ground chrysoberyl in an electric furnace at 1780ºC in an oxidizing atmosphere for 50 hours. The chromium-doped corundum, containing around 160-210 ppm by weight of Cr with negligible concentrations of other trace elements, was also irradiated with X-rays (80 kV, 4mA) for 4 hours, then faded for 4 hours with a 100-watt light bulb, and subsequently heat treated with ground chrysoberyl at unspecified conditions by a Thai treater. At each stage of the experiments, the samples were photographed and UV-Vis absorption spectra were recorded.
Both the irradiation and Be-diffusion experiments on the iron-doped synthetic corundum created defect centers that had similar UV-Vis absorption curves and produced yellow coloration. The yellow color was unstable when induced by irradiation, but was stable after Be-diffusion.
Experiments on the chromium-doped synthetic corundum produced orange coloration (and similar UV-Vis absorption patterns) by both irradiation and Be-diffusion heating methods. Again, the orange color was unstable when induced by irradiation (and quickly faded to pink), but remained stable after Be-diffusion. These results confirm that divalent Be acts as a stabilizer of defect centers or color centers in iron-doped and chromium-doped synthetic corundum. Hence, the spectrum produced by the irradiation of Fe-doped or Cr-doped synthetic corundum was attributed to metal-related unstable color centers, while that produced in synthetic corundum doped with Be + Fe + or Be + Cr was caused by Be²+ + metal-related stable color centers.
Visut Pisutha Arnond, Tobias Hager, Pornsawat Wathankul, Wilawan Atichat, Jitrin Nattachai, Chakkaphant Sutthirat, and Bootawee Sriprasert writes:
X-radiation and Be-diffusion heating experiments were performed on an iron-doped (colorless) synthetic corundum and a chromium-doped (pink) synthetic corundum to evaluate the role of beryllium in causing color in the Be-Fe-Al2O3 and Be-Cr-Al2O3 systems.
The iron-doped corundum, containing around 140-170 ppm by weight of Fe with negligible concentrations of other trace elements, was irradiated with X-rays (60 kV, 53 mA) for 30 minutes, then the color was faded for one hour with a 100-watt light bulb, and finally the sample was heat treated in a crucible with ground chrysoberyl in an electric furnace at 1780ºC in an oxidizing atmosphere for 50 hours. The chromium-doped corundum, containing around 160-210 ppm by weight of Cr with negligible concentrations of other trace elements, was also irradiated with X-rays (80 kV, 4mA) for 4 hours, then faded for 4 hours with a 100-watt light bulb, and subsequently heat treated with ground chrysoberyl at unspecified conditions by a Thai treater. At each stage of the experiments, the samples were photographed and UV-Vis absorption spectra were recorded.
Both the irradiation and Be-diffusion experiments on the iron-doped synthetic corundum created defect centers that had similar UV-Vis absorption curves and produced yellow coloration. The yellow color was unstable when induced by irradiation, but was stable after Be-diffusion.
Experiments on the chromium-doped synthetic corundum produced orange coloration (and similar UV-Vis absorption patterns) by both irradiation and Be-diffusion heating methods. Again, the orange color was unstable when induced by irradiation (and quickly faded to pink), but remained stable after Be-diffusion. These results confirm that divalent Be acts as a stabilizer of defect centers or color centers in iron-doped and chromium-doped synthetic corundum. Hence, the spectrum produced by the irradiation of Fe-doped or Cr-doped synthetic corundum was attributed to metal-related unstable color centers, while that produced in synthetic corundum doped with Be + Fe + or Be + Cr was caused by Be²+ + metal-related stable color centers.
Friday, June 08, 2007
The Hidden Transparency
Chaim Even-Zohar writes about supplier of choice contracts + DTC's problems communicating with the sightholders @ http://www.idexonline.com/portal_FullEditorial.asp
Subjectivity In Gemology
How true! In a way gemology is a magic blend of subjectivity + objectivity + the expert who knows how to connect with the world makes all the difference in a day. Can anyone express the allure, fineness, attraction and glamor in alpha numerical notation? I doubt it.
Ronald Ringsrud (Ronald Ringsrud Co, California) writes:
The analytical mind cannot encapsulate the full experience of viewing a beautiful gem. The detailed objective perceptions of the intellect are supplemented by another style of perception—that of subjective perception. It is holistic and devoid of the mental activity of analysis.
Connoisseurs of gems develop the ability, during a lifetime of viewing fine gems, to go beyond the boundaries of the intellect and witness the glorious aesthetics that a fine gemstone has to offer. From a physiological standpoint, this could be called shifting from brain activity dominated by the left hemisphere (responsible for analysis and discrimination) to that of the right hemisphere (contextual and nonverbal functions).
Gemology’s fullest expression as a discipline is exemplified when both objective and subjective approaches are used. Therefore, physics, optics, and chemistry are taught in gemological institutes alongside history, romance, and folklore. The work of gemologists Dr Edward Gubelin expressed not only objective science but also subjectivity; gemstone certificates from his laboratory had the usual page of objective determinations for the gemstone, but also a page of subjective description outlining the beauty, uniqueness, rarity of the gem.
Dr Gubelin went to encourage work in the use of poetry to describe gemstone aesthetics, which, in an industry sustained by the romancing sale of gemstones, should be recognized as worthy of the highest endeavor.
Fredrick Kunz decried the arbitrary alteration of the birthstone chart by an association of jewelers in 1912. He recognized the multicultural reality that gemstones are special to people born on certain months. Modern understanding of an ancient eastern astrological system sheds new light on this. Practitioners of traditional Asian medicine prescribed gems not only as talismans but also as pharmaceuticals.
Gemology is perhaps more suited to address subjectivity than other sciences simply because its focus, gemstones, involves the complete expressions of the highest subjective qualities: allure, fineness, attraction, glamour, and charm. The role of subjectivity in gemology is interdisciplinary and should elevate our expectations of future gemologists and gemstone dealers.
Ronald Ringsrud (Ronald Ringsrud Co, California) writes:
The analytical mind cannot encapsulate the full experience of viewing a beautiful gem. The detailed objective perceptions of the intellect are supplemented by another style of perception—that of subjective perception. It is holistic and devoid of the mental activity of analysis.
Connoisseurs of gems develop the ability, during a lifetime of viewing fine gems, to go beyond the boundaries of the intellect and witness the glorious aesthetics that a fine gemstone has to offer. From a physiological standpoint, this could be called shifting from brain activity dominated by the left hemisphere (responsible for analysis and discrimination) to that of the right hemisphere (contextual and nonverbal functions).
Gemology’s fullest expression as a discipline is exemplified when both objective and subjective approaches are used. Therefore, physics, optics, and chemistry are taught in gemological institutes alongside history, romance, and folklore. The work of gemologists Dr Edward Gubelin expressed not only objective science but also subjectivity; gemstone certificates from his laboratory had the usual page of objective determinations for the gemstone, but also a page of subjective description outlining the beauty, uniqueness, rarity of the gem.
Dr Gubelin went to encourage work in the use of poetry to describe gemstone aesthetics, which, in an industry sustained by the romancing sale of gemstones, should be recognized as worthy of the highest endeavor.
Fredrick Kunz decried the arbitrary alteration of the birthstone chart by an association of jewelers in 1912. He recognized the multicultural reality that gemstones are special to people born on certain months. Modern understanding of an ancient eastern astrological system sheds new light on this. Practitioners of traditional Asian medicine prescribed gems not only as talismans but also as pharmaceuticals.
Gemology is perhaps more suited to address subjectivity than other sciences simply because its focus, gemstones, involves the complete expressions of the highest subjective qualities: allure, fineness, attraction, glamour, and charm. The role of subjectivity in gemology is interdisciplinary and should elevate our expectations of future gemologists and gemstone dealers.
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