REVIEW BOARD Emmanuel Fritsch Marv L. Johnson Himiko Naka University of Nantes, France GIAG~~Trade Lab, Santa Monica Pacific Palisades, California Charles E, Ashbaugh Ill Isotope Products Laboratories Michael Gray A. A. Levinson Gary A. Roskin Burbank, California Missoula, Montana University 01 Calgary European Gemological Laboratory Calgary, Alberta, Canada Los Angeles, California Andrew Christie Patricia A, S, Gray Loretta B, Loeb James E. Shigley GIA, Santa Monica GIA, Santa Monica Missoula, Montana Visalia, California Carol M. Stockton Jo Ellen Cole Elise B. Misiorowski GIA, Santa Monica Professor R. A. Howie GIA, Santa Monica Alexandria, Virginia Royal Holloway Rolf Tatje Maha DeMaggio University of London Jana E. Miyahira Duisburg University GIA Gem Trade Lab, Santa Monica United Kingdom GIA, Santa Monica Duisburg, Germany

COLORED STONES AND Townsendl. In disagreement- with traditional theories of ORGANIC MATERIALS opal formation, Len Cram offers a surprising new model, based on ion exchange, that he demonstrated by growing Cretaceous mushrooms in amber. D. S. Hibbett, D. synthetic opal out of "opal dirt" in a bottle in just three Grimaldi, and M. J. Donaghue, Nature, October 12, months. Jiirgen Schutz describes the long history of 1995, p. 487. Mexican opals, their varieties, and the present mining sit- Recently, two mushrooms were discovered in amber of uation. Jochen Knigge recounts the history and produc- Turonian age (90-94 million years old, mid-Cretaceous] in tion of opals from Pedro 11, Piaui, Brazil. Klaus Eberhard central New Jersey. One specimen is nearly complete, with Wild portrays another important locality-Kirschweiler, an intact cap, distinct gills, and a central stalk (itis the old- near Idar-Oberstein-which was (and perhaps still is] one est known such mushroom, by about 60 donyears); the of the most important centers of opal fashioning and other is a wedge-shaped fragment of a mushroom cap. Both trade worldwide. mushrooms resemble modern common leaf-litter and Jiirgen Schiitz explains the factors that determine the wood-decayer species, and both were growing on a cedar (a price of an opal (localityof origin, body color, play-of-color, member of the Cupressaceae family). ML/

Opal. extrdapis, No. 10, 1996, 96 pp. [In German]. This section is designed to provide as complete a record as prac- Opal is the subject of another extraLapis, an issue of tical of the recent literature on gems and gemology Articles are selected for abstracting solely at the discretion of the section edi- Lapis magazine that is devoted entirely to one gemstone. tor and his reviewers, and space limitations may require that we Following a comprehensive introduction by Edward include only those articles that we feel will be of greatest interest Giibelin, a series of articles provide information on all to our readership. important aspects of ths colorful gem. Inquiries for reprints of articles abstracted must be addressed to An article by Max Weibel explains the origin of play- the author or publisher of the original material. of-color. Two other papers describe Queensland's boulder The reviewer of each article is identified by his or her initials at the opals, their forms, production, and prospecting methods end of each abstract. Guest reviewers are identified by their full (WilsonCooper and Barry J. Neville); and the geologic set- names. Opinions expressed in an abstract belong to the abstrac- ter and in no way reflect the position of Gems & Gemology or GIA. ting and processes that led to opal formation in the sedi- 0 7996 Gemological Institute of America ments of Australia's Great Artesian Basin (Jack

Gemological Abstracts GEMS & GEMOLOGY Fall 1996 225 pattern, cut, size). Even with these criteria, it remains dif- ore, at a valuation of $58.17 per carat. Bulk sampling is ficult to know how much a harlequin opal is really worth. proceeding at the A-154 South, A-154 North, and A-21 Three additional articles provide information on opal lzimberlites. MLf nomenclature (Jurgen Schutz and Manfred Szykora); dou- blets, triplets, and opal mosaics (Karl Fischer]; and synthet- Diamonds everywhere. C. Koeberl, Nature, November 2, ic opals and opal simulants (Manfred Szylzora].The volume 1995, pp. 17-18. concludes with a description of opalized fossils: snails, On Earth, diamonds usually occur in rocks derived from mussels, belemnites, and even dinosaurs [Alex Ritchie and the mantle. They are thought to have formed from fluids Brigitte Szylzora). or melts in the upper mantle at "immense" temperatures This extraLapis also contains short descriptions of and pressures, probably-according to Mr. Koebcrl-dur- smaller opal sources [Denmark, Honduras, Indonesia, ing several diamond-forming events early in the Earth's Mali, Saxony, Slovakia [formerly Hungary], Turkey, and history. Diamonds have also been produced, directly on the United States]; an opal glossary; and the stories of the the Earth's surface, during meteorite impacts; such dia- Hope and El hila Azteca opals (by John S. White). Also monds may have formed, at least in one case [Ries described is an extraordinary opal necklace that Queen Crater), from the vapor phase. Diamonds found in iron Elizabeth I1 was not given as a coronation present (by meteorites and ureilites [another variety of meteorite) Helmut Weis]. Two stories tell us how Australian aborig- were formed by shock from graphite or an~orphouscar- ines explain the origin of opals. bon, probably in the meteorite and not after it arrived on A volume about opals with words only (in this case, the Earth. Nanometer-size diamonds have been found in German) would be utterly frustrating. In this edition, chondritic meteorites, associated with noble gases however, the stunning beauty and incredible variability [xenon, argon, etc.] with unusual isotopic compositionsj of opals is illustrated throughout the entire volume by these came from interstellar or presolar events very early wonderful color photographs. RT in the history of the solar system. Small diamonds have also been found in clays marking the boundary of the Zur Entstehung der sternfoermigen Achate in sauren Cretaceous and Tertiary periods, which has evidence of a Vulkaniten. Eine modifizierte Bildungstheorie (The large impact; their carbon and nitrogen isotopes point to origin of star-shaped agates in acidic vulcanites. A an origin within the impact event or the resulting fireball. modified theory of formation). R, Rykart, Der Polycrystalline diamonds up to 1 cm, discovered in Aufschluss, Vol. 46, 1995, pp. 33-36. impactites at a few Russian and Ukrainian impact stnrc- It has generally been believed that agate formation in rhy- tures, also appear to be crustal in origin. Impact-produced elites and porphyries takes place at high temperatures. diamonds are very different from microdiamonds found Recent research by M. Landmesser has shown that agate in high-grade inctamorphic rocks. may form in other types of rocks at lower temperatures. In Also rare and unusual are polycrystalline black dia- this article, Mr. Rylzart proposes a new theory for the for- monds, called carbonados. No carbonado diamond has mation of star-shaped agates in lithophysae (e.g., thunder ever been found in situ in a rock. Possible origins include eggs] in rhyolitic vulcanites. The basic idea is that the carbon subduction in the mantle, shock metamorphism gaseous bubbles in the magma contract to form polygonal during impact, or irradiation of organic matter; vapor- cavities because of dropping gas pressure during cooling deposition may also be a candidate. MLJ near the Earth's surface. Subsequently, monomer H4Si04, dissolved in the water that invades the cavities, fills them Diamonds: Wyoming's best friend. Geotimes, Vol. 41, with chalcedony and quartz. The surrounding rhyolite No. 2, February 1996, pp. 9-10. devitrifies and hardens, forming the well-known quartz porphyry kills. RT The first diamond mine in Wyoming is about to begin pro- duction, and many more lumberlites and lamproites in the DIAMONDS region may contain diamonds, according to W. Dan Hausel of the Wyoming State Geological Survey. Redaurum Red Aber Resources Ltd. Diamond Industry Week, February Lake has just finished construction of a 140-ton-per-hour 26, 1996, p. 3. ore-processing ~LUfor the cornpanyls Kelsey Lalze di'mond Aber Resources has announced results from drill cores at property, along the Colorado-Wyoming state line; several A-418, one of their lumberlite pipes in the Northwest gem diamonds, up to 14.2 ct, already have been recovered Territories, Canada. Nineteen tons of ore in a large-diain- from this property. The Colorado-Wyoming lumberlite eter (6 inches, about 15 cm] core drilled through 367 m of province includes more than 100 lumberlite intrusives, one lumberlite yielded 83.1 carats of diamonds-4.3 carats per of the world's largest lamproite fields, and dozens of unex- ton of ore-with individual stones between 0.025 and 3 plored geophysical and geochemical anomalies. More than carats. The largest "gem" diamond weighed 2.2 carats. 120,000 diamonds have been recovered from this area in the The A-418 pipe is estimated to contain 15 million tons of last 20 years. ore to 650 in depth; the grade is similar to that of the A- No history of diamond mining in Wyoming is con~plete 154 South lzin~berlite,which showed 4.5 carats per ton of without mention of the "Great Diamond Hoax of 1872." A

226 Gemological Abstracts GEMS & GEMOLOGY Fall 1996 sandstone outcrop was salted with 10 pounds of uncut dia- The authors note the paucity of published research monds and rubies (purchased in London), plus another 50 into nitrogen content and the aggregation and carbon-iso- pounds of garnets and chrome-rich diopsides from Arizona. tope composition of microdiamonds, by which their (At the time, sandstone was thought to be a host rock for dia- hypothesis could be tested. Very recently, a number of monds, no doubt based on the many alluvial diamond papers (by researchers such as Milledge, Mendelssohn, sources then known.) This hoax helped provoke passage of Taylor, and Pillinger, among others) have addressed these the Mining Law of 1872, which established the first niine- subjects, but not the specific issue of euhedral rnicrodia- patenting regulations in this country. Full details of the story monds. However, this interesting review and thought-pro- may be found in the Wyoming Geological Association's voicing hypothesis may give a welcome impetus to the 1995 Field Conference Guidebook. MLJ release of more information on microdiamonds and their usefulness in estimating diamond content. Bram Janse Are euhedral microdiamonds formed during ascent and decompression of kimberlite magma? Implications French Guiana diamonds. Mining Journal, London, for use of microdiamonds in diamond grade esti- March 22, 1996, p. 212. mation. D. R. M. Pattison and A. A. Levinson, Diamonds have been found in a metamorphosed ultra- Applied Geochemistry, Vol. 10, 1995, pp. 725-738. mafic rock in the Dachine permit area, Inini, French The authors answer this question with "Yes, quite likely Guiana. Golden Star Resources, Guyanor Resources SA, in some cases." Before they proceed with their explana- and Lakefield Research have recovered 3,748 microdia- tion, they first state clearly that this paper only discusses monds from over 113 kg of host rock; also, 8 macrodia- transparent, well-crystallized, euhedral octahedral stones monds (the largest being 2.4 mm) have been recovered smaller than 1 mm (so-called microdiamoncls), which from 1.8 tons of rock altered to saprolite. ML1 show little or no signs of resorption. No broken stones, fragments, or crystal shards are considered. ODM: Namibian gem. Mining Journal, London, March In a detailed review of several theories about the ori- 15, 1996, p. 205. gin of euhedral microdiamonds (break-upof peridotitic or Several companies have licenses to mine the diamond- eclogitic xenoliths, resorption of larger diamonds, precip- rich offshore deposits along the Namibian and South itation from melts of inetasomatic events), the authors African coasts: De Beers Marine (which produces the show that none of these satisfactorily explains the pres- most stones at this time, about 0.5 million carats), ence of both resorbed macrodiamonds (larger than 1 mm) Namibian Minerals Corp., Diamond Fields Resources, and euhedral microdiamonds in a single lumberlite pipe. BHP, and Ocean Diamond Mining [ODM),plus a few oth- They argue that if diamonds are resorbed in a lzimberlite ers. Capetown-based ODM is an "important, but under- magma, the microdiamonds would be resorbed more, reported" company operating in the region. ODM cur- possibly to extinction, and there would be no euhedral rently works in two main areas: It has production around microdian~onds. The authors propose a hypothesis: the 12 Penguin Islands, and exploration along South Varying pressure-temperature and oxidation conditions African concession 7b and deep-water concessions 6c and generate (at different times) resorption of existing macro- 14c (in a joint venture with Benguela Concessions). and microdian~onds,followed by crystallization of euhe- Production in fiscal 1995 was about 40,000 carats at an dral microdiamonds from carbon dispersed in the magma average price of US$200 per carat. ML1 and, to a lesser extent, from carbon released by the resorp- tion of pre-existing diamonds. The process can be multi- GEM LOCALITIES stage and can produce different mixtures of stones in dif- ferent pipes, ranging from the extremes of only rounded Alkali basalts and associated volcaniclastic rocks as a source resorbed n~acrodiamondsand no n~icrodiamondsto no of sapphire in eastern Australia. G. M. Oakes, L. M. macrodiamonds (resorbed to extinction) and only euhe- Ban-on, and S. R. Lishrn~md,Australian Journal of dral microdiamonds. Thus, the relationship between the Earth Sciences, Vol. 43, No. 3, 1996, pp. 289-298. population of n~acrodiamonds and that of euhedral The major sapphire deposits in eastern Australia are allu- microdicimonds is not simple and direct. vial; they occur in recent drainage systems where Tertiary The implication is that the use of microdian~ondsin alkali basaltic volcanic rocks dominate the present surface. estimating the overall diamond content in a pipe (which As a result, it has been generally accepted that these is widely done in Canada, where pipes are buried and only basalts are the immediate source of the sapphires. The drill core samples are available fortesting) is not straight- enigma is that sapphires are only rarely found in these forward. In several cases, this method can give an incor- rocks. This paper discusses recent developments in the rect answer. Diamond exploration companies' arguments understanding of sapphire occurrences in eastern that the method does work rest on their use of the ratios Australia and reviews several possible origins for these of euhedral, resorbed, and cubic microdiamonds, as well deposits. as broken and fragmented crystals. However, this privi- During field studies, it was observed that the sap- leged information is not available in published form, so it phires are associated with volcaniclastic rock units, now is impossible to confirm their arguments. mostly altered to clay minerals, that are common within

Gemological Abstracts GEMS & GEMOLOGY Fall 1996 227 the main basaltic sequences. [Volcaniclas~icmeans a Country summaries. African Mining Supplement to rock composed of volcanic fragments, and includes such Mining Journal, London, January 26, 1996, pp. 7, 9, rock types as ash, tuff, or breccia). The volcaniclastic 13, 15, 17, 19, 21, 23. units are laterally extensive, but they are thin, easily This article summarizes mining activities, by country, for eroded, and generally poorly exposed. In some locations, African nations in 1994. Reports relevant to gemstones- however, extraordinary concentrations of sapphires (up to primarily diamonds-include those for: 12 kg per cubic meter) have been observed within these Angola, where only state-owned Endiama, or its units. These volcaniclastic roclzs are the products of the joint ventures, can hold diamond-mining rights. Alluvial early explosive stages of the basaltic volcanic episodes of mining totaled 1.25 million carats (Mct)in 1992, but offi- eastern Australia, and they are chemically distinct (i.e., cial production has collapsed since. "more fractionated") from the surface basalts that are Botswana, the second biggest producer of gem dia- products of quieter episodes. monds after Russia. Recovery from Jwaneng, Orapa, and The Tertiary volcaniclastic rock units constitute Letlhalzane rose 6%) to 15.5 Mct in 1994. The value of prime exploration targets for alluvial sapphires (and asso- diamond exports rose 1%, to US$1.4 billion. ciated minerals such as zircon and spinel) in eastern The Central African Republic, with official produc- Australia and possibly in similar geologic provinces else- tion figures of 530,000 carats annually. where (e.g., Southeast Asia). AA L Congo, where traces of diamonds were found near the border with the Central African Republic and on the Alkaline rocks and gemstones, Australia: A review and island of M'bainu, near Brazzaville. synthesis. F. L. Sutherland, Australian Journal of Ivory Coast, where two diamond mines, at Tortiya Earth Sciences, Vol. 43, No. 3, 1996, pp. 323-343. and Skguela, produce about 15,000 carats annually. Valuable gemstones that occur in Australian alkaline Ghana, which produced about 750,000 carats of roclzs include diamonds in lamproites and lumberlites; diamonds in 1994. sapphires, zircons, and rubies in alkali basalts; and one Guinea; production at Aredor's diamond mine at gem zircon prospect in carbonatite. This paper reviews Banankoro was suspended in 1994. the tectonic settings and origins of Australia's gem-bear- Liberia, where illicit gold- and diamond-mining ing alkaline roclzs. activity continued around the Lofa River, on the border There are marked contrasts between diamond and with Sierra Leone. sapphire-zircon associations across the continent. Most Malawi, which continues to have "extremely lirnit- western cratonic areas exhibit episodic, sparse, deep allza- ed" production. line activity from the diamond zone (2 billion-20 million Mali; 20 kimberlite pipes have been found in the years [My] old). However, in eastern fold-belt areas, pro- southwest, but no production has begun. lific Mesozoic/Cenozoic basaltic volcanism carried up Namibia, a major diamond producer (over one-third considerable amounts of sapphire and zircon (since 170 of its export income comes from diamonds). Production My). Some South Australian Mesozoic lumberlitic dia- from onshore and offshore deposits rose 15% in 1994, to mond events (180-170 My) represent ultra-deep material 1.31 Mct (95% of which was gem quality), mostly from rising through the mantle transition zone. Eastern Namdeb (or its predecessor Consolidated Diamond Mines). Australian diamonds are unusual; at present, their origin Sierra Leone; diamond production from the eastern is in dispute. Several different models compete to explain Kono region generated 255,000 carats of exported dia- sapphire/zircon formation in eastern Australia. These monds, valued at US$30.2 million. Civil unrest disrupted range from eruptive plucking of metamorphosed sub- mining in most other areas. ducted materials to crystallization from felsic melts to South Africa, which produced 10.8 Mct of diamonds carbonatitic reactions. Pb-U isotopic zircon ages favor for- in 1994, split 90%-9%-1% among lumberlites, alluvial mation during Phanerozoic basaltic activity and not d~u- mines, and offshore production. ing earlier Paleozoic subduction or granitic-intrusion Swaziland; the Dolokwayo mine processes 600,000 events. A problem for the theory that zircon crystallized tons of diamond ore per year (but no production figures from fractionated basaltic melts is negligible Eu depletion were given). in rare-earth-element patterns. Tanzania, where production at the dilapidated The authors propose a model that favors sapphire/ Williamson mine fell to 22,567 carats in 1994. However, zircon crystallization from relatively small-volume, lit- changes in ownership may lead to overhaul, and explo- tle-evolved, felsic melts that are generated from metaso- ration continues. matized mantle as the lithosphere overruns subdued hot Zaire, where 16 Mct of diamonds were produced- spot systems, initiated at Tasman-Coral Sea margins. A 11 Mct from artisanal working and 5 Mct from the unique ruby, sapphire, sapphirine, spinel assemblage Bakwanga (Miba]mines. Coffee is now the leading export. from the Barrington basalt shield in New South Wales Zimbabwe; Auridiam produced 15,000 carats from marks a separate ruby/pastel-colored-sapphiregenesis. the River Ranch deposit. Two-thirds of the country is cov- RA H ered with prospecting orders, mostly for diamonds. MLJ

228 Gemological Abstracts GEMS & GEMOLOGY Fall 1996 An evaporitic origin of the parent brines of Colombian foreign investors the right to exploit certain mineral emeralds: Fluid inclusion and sulphur isotope evi- resources, including gemstones. The law gives foreign dence. G. Giuliani, A. Cheilletz, C. Arboleda, V. companies the right to "store, transport, consume domes- Carillo, F. Rueda, and J. H. Baker, European Journal tically and export minerals they exploit." However, the of Mineralogy, Vol. 7, No. 1, 1995, pp. 151-165. first enforcement activity is expected to be aimed at This paper presents the results of microthermometry, SEM, small-scale operations in regions overrun by fortune seek- and Raman probe examination of emeralds and gangue min- ers: In particular, the conditions of child laborers in min- erals, as well as the first sulfur isotopic data on pyrite, from ing camps-primarily gold mining camps~inthe north of seven Colombian emerald deposits. Also discussed is the the country will be addressed. MLJ origin of the hydrothermal fluids that formed the carbonate- pyrite-emerald vein mineralization in Colombia. INSTRUMENTS AND TECHNIQUES The fluid-inclusion study shows the presence of homo- Scanning near-field optical microscopy (SNOM) and its geneous and hypersaline brines; the isotope study suggests a application in mineralogy. W. Gutmannsbauer, T. uniform sulfur isotopic composition for the fluids and a H~iser,T. Lacoste, H. Heinzelmann, and H.-J. heavy, probably unique, sulfide-sulfur source for emerald Guntherodt, 1995, Schweizerische Mineralogische deposits of both the western and eastern emerald zones. und Petrograpl~ischeMitteleitung,Vol. 75, pp. Considering the presence of salt diapirs and gypsum diapirs 259-264. in the area, the authors conclude that "the only likely and The technique described uses visible radiation (light] to unique source of sulphur might be derived from evaporites observe sub-micron-sized features in mineral samples. through a sulphate reduction process at the site of mineral precipitation." These results, together with those of previ- Bluish green light from an argon-ion laser is transmitted an nrn ous studies, support the interpretation of hydrothermal though optic fiber with a very narrow tip (around 50 emerald mineralization in a sedimentary environment. In in diameter); the tip is scanned across the sample, and light that respect, the Colombian emerald deposits differ dramat- transmitted through the sample is collected and displayed ically from almost all other emerald sources. RT as a function of position. The resulting two-dimensional image" has a resolution on the order of 0.5 micron or better. Opal safari. J. F. Watson, Australian Gold Gem 0) The authors examined 25-micron-thick transparent Treasure, Vol. 11, No. 2, February 1996, pp. 27-31. thin sections (with parallel front and back faces) for this paper, but they believe that reflected light could also be Mining for blaclz opals continues in the area of New collected, enabling study of opaque samples. The tech- South Wales, Australia. Although Lightning Ridge proper nique could be adapted to multi-wavelength (color] obser- is the most popular tourist destination, the author visited vation if a tunable laser were used; it should also be adapt- the more remote opal fields at Grawin, Glengarry, and able for fluorescence, cathodoluminescence, Raman spec- Sheep Yards. Most of the miners in the Grawin and Sheep troscopy, and infrared spectroscopy. As described in this Yards area dig down 9-12 nl to reach the working level. Prospecting entails two stages: A drilling rig makes a 17.5- paper, however, the potential usefulness of this technique cm-diameter test hole down to the working level; if the in gem testing is very limited, as the sample must be a hole looks promising, a 1-m-diameter shaft is drilled after transparent, well-polished thin section. MLJ the claim is registered. Most of the opal mined is "potch," or common opal, JEWELRY RETAILING usually gray, "amber," or black; a black-and-white variety Saleroom report: June results buoy London market. Retail is known locally as "magpie" potch. Only 5% shows play- Jeweller, July 11, 1996, p. 8. of-color, and only 5% of that (0.25%altogether) is classified June was a bumper month for London jewelry sales; as "precious gem quality" opal. Gem opal sitting on black Christie's and Phillips both did well. Christie's June 19 sale potch is the most desirable. was the greater success, with a £4,299,97 total. Buyers The Grawin opal fields were discovered in 1907, and from 26 counties competed actively on the phone, in the all three opal fields [Grawin, Glengarry, and Sheep Yards] room, and in the book; more than 60% were private clients. have been extensively mined. However, amateur collectors A pair of rare antique Indian diamond briolettes more continue to find opals in the "mulloclz heaps" [dumps). than doubled their estimate, to sell to the trade at The author warns the unwary of the area's many £15,500. An antique emerald, diamond, and pearl neclz- unmarked mine shafts; a fall down one is almost certain- lace, estimated at £30,000-£35,0 brought in £89,500 ly fatal. In nearby Cumborah, "crystal clear" quartz and and a fancy intense yellow diamond ring-estimated at petrified wood can be collected. MLJ £40,000-£50,000-so to an anonymous buyer for £122,500A typical Belle Epoque garland-style diamond Vietnam's illegal miners. Mining Journal, London, April necklace brought an extraordinarily high £73,000The 5, 1996, p. 252. overflow from these refined Christie's sales goes to the Vietnam's National Assembly passed a new mining law, ever-popular Christie's South Kensington, which boasted scheduled to take effect in September 1996, that grants its best-ever sale on June 18.

Gemological Abstracts GEMS & GEMOLOGY Fall 1996 229 Phillips's fine jewelry sale on June 27 was highlighted Although not mentioned in this comprehensive arti- by a group of 19th-century jewels by French gothic-revival cle, the possible consequences for gemology (e.g., the goldsmith Louis Wiese. A heavy neo-gothic bangle, coating of gems, especially diamond simulants) should be mounted with a large cabochon sapphire and flanked by kept in mind. RT leopard heads, went above estimate for £21,850A gold lozenge-shaped brooch with matching ring, again set with UF engineers' patented process makes world's largest syn- cabochon sapphires and with pearls, sold for £6,670 A thetic diamond. Diamond Industry Week, February heavy neo-Renaissance gold, cameo, and pearl locket and 12, 1996, p. 1. chain made £26,450Buyers also showed a good appetite Researchers James Adair and Rajiv Singh at the for old-cut Victorian diamonds. A diamond riviere neclc- University of Florida (and their coworkers and industrial lace from about 1880 sold for £10,350more than doubling collaborators) have made the largest synthetic diamond its estimate. A late-Victorian pearl and diamond bangle, known to date-about 1600 ct. It was grown by a low- estimated at £1,200-£1,50 sold for £3,220Solitaire dia- temperature (to cis low as 500°Cvapor-deposition tech- mond rings sold particularly well to private buyers, MD nique; color and clarity were not specified, but its dimen- sions (11 inches [about 28 cm] in diameter and 1.5 min SYNTHETICS AND SIMULANTS thick) would seem to preclude any gemstone application, The prospects for large-scale diamond coatings look very Harder than diamond? R. W. Cahn, Nature, March 14, promising, however. MLl 1996, pp. 104-105. Theorists have predicted a structure of carbon nitride that should be harder than diamond, and experimentalists are TREATMENTS trying to make it. The predicted material, cubic C3N4, A fact of life: Treatments are forever. Mazal U'Bracha, has the same structure as SiiN4. Attempts to make this No. 79, June 1996, pp. 33-40. compound by vapor deposition have been hampered by Highlights of the 27th World Diamond Congress in Tel the difficulty in getting enough nitrogen into the materi- Aviv included the general agreement that a standard al; graphite-like structures and films with triple-bonded nomenclature must be devised to cope with the rising [acetylene-like)carbon form instead. Annealing of the lat- numbers of fracture-filled, enhanced, and treated dia- ter gets rid of the triple bonds and produces a film that has monds entering the market. Some congress members dian~ond-likeelectrical properties but much lower hard- expressed concern about fracture-filled rough; Howard ness than diamond thin films. It is possible that "s~iper- Vaughan of De Beers said that the CSO would never sell hard" C&, can be produced by high-pressure synthesis treated or filled rough. He added, however, that De Beers methods. ML1 could not prevent manufacturers from treating or filling rough they had purchased from De Beers. Metastable diamond synthesis-Principles and applica- In other action, a trade development committee of tions. C.-P. Klages, European Journal of Mineralogy, international diamond dealers was formed to promote Vol. 7, No. 4, 1995, pp. 767-774. "exchange" (presumably an exchange of ideas, although Chemical vapor deposition (CVD]of diamond films from the article does not say specifically) with developing activated gas phases was first achieved in 1952-53, but Asian markets. The World Federation of Diamond only since 1983 has it become an important and rapidly Bourses agreed to look into the feasibility of creating a developing field of research. This paper summarizes the computer network. principles, results, and perspectives of CVD technology. It Addressing the Israeli Diamond Manufacturers starts with a description of the conditions in which dia- Association, Yvegeny Bychkov, head of the Association of mond thin films crystallize from gas phases and the many Russian Diamond Manufacturers, noted that Russia is deposition processes now available. The growth of tex- the only country that both mines (about US$1.4 billion in tured and hetero-epitaxial diamond films on different 1995) and cuts a substantial amount of diamonds. substrates, especially silicon, is discussed and illustrated Twenty-five percent of all diamonds mined are Russian, with scanning electron micrographs. The author then and 7,000 people are employed by Russia's 60 manufac- outlines the many applications of diamond films (from turers. Although Mr. Bychkov predicted that Russia high-frequency electronic devices to optical filters to would expand its cutting operations, he also warned that membranes for loudspeakers) and gives an outlook on the fledgling industry could be strangled by "hard condi- their future potential. tions imposed by De Beers." AC

230 Gemological Abstracts GEMS &. GEMOLOGY Fall 1996