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34th International Gemmological Conference.

The 34th biennial IGC took place in Vilnius, Lithuania, on 26-30 August 2015. The conference was organized by Dr Arunas Kleismantas (Vilnius University, Lithuania), Vilma Misiukoniene (Infobalt Lithuania, Vilnius) and Dr Jayshree Panjikar (PANGEMTECH, Pune, India) in collaboration with Vilnius University and duSafyrai gem laboratory and museum in Vilnius. Approximately 75 delegates, observers and guests gathered for the event (Figure 1), and some of them attended pre- and post-conference field trips. Individual abstracts of the oral and poster presentations, as well as the entire proceedings volume, can be downloaded at www.igc-gemmology.net/proceedings.

Lithuania is a source of Baltic amber, and several presentations focused on amber from this region and elsewhere. Dr Sigitas Podenas (Vilnius University, Lithuania) reviewed the broad diversity of crane flies preserved as inclusions in Baltic amber. A total of 160 species representing five genera have been identified, and these lived during the latter part of the Eocene epoch, approximately 54 to 44 million years ago. Dr Albertas Bitinas (Klaipeda University, Lithuania) covered the geological origin of amber in the southeast Baltic Sea region. The deposits originated from resin of a Pinus succinifera forest and were transported by rivers and then deposited in deltas. Today, amber is known to exist in a 2-m-thick layer of silty sands on the Sambia Peninsula in the Kaliningrad area of Russia, at a depth of 10 m below the present sea level. Erosion of this layer during periods of lower sea level (approximately six million years ago) released some of the amber into the Baltic Sea, where it was eventually redeposited in offshore spits and lagoons. Dr Jonas Satkunas (Lithuanian Geological Survey, Vilnius) discussed amber production in Lithuania, beginning with the 1858 establishment of Stantien & Becker for gathering amber from the northern part of the Curonian Lagoon. More recently, in 1992-1994, exploration by the Lithuanian Geological Survey near the town of Klaipeda identified an inferred resource of 227 tonnes that could produce an estimated 2030 tonnes/year of amber, but mining in this area is currently restricted so it is unlikely that the deposits will be exploited. Willow Wight (Canadian Museum of Nature, Ottawa) reviewed Canadian amber localities. Although not commercially important, deposits are known at Cedar Lake in Manitoba (Late Cretaceous) and from three sites in the Canadian Arctic (Eocene). Dr Lore Kiefert (Gubelin Gem Lab, Lucerne, Switzerland) discussed natural-colour green amber from central Ethiopia, which was discovered in 2010 in Cretaceous sediments that are overlain by Tertiary basalt. It is hypothesized that heat from the basalt flow caused the green coloration of the amber. Tay Thye Sun (Far East Gemological Laboratory, Singapore) and co-authors characterized Burmese amber from a relatively new locality near Hti Lin (see article on pp. 606-615 of this issue of The Journal).

In diamond presentations, Dr Thomas Hainschwang (GGTL Laboratories, Balzers, Liechtenstein) and co-authors examined unusual black diamonds containing inclusions of lonsdaleite (the hexagonal polymorph of diamond) and CO2. Although such diamonds may be mistakenly identified as synthetic based on the one-phonon region of their infrared spectra, they actually consist of polycrystalline aggregates of natural diamond that are heavily included by non-diamond carbon. Dr Hiroshi Kitawaki (Central Gem Laboratory, Tokyo, Japan) and coauthors described type lb yellow to brownish yellow CVD synthetic diamonds (see article on pp. 594-604 of this issue of The Journal). Dr Joe C. C. Yuan (Taiwan Gemmological Institute, Taipei; and Solstar Diamond Co. and Taidiam Technology, Zhengzhou, China) predicted that high pressure, high temperature (HPHT)-grown synthetic diamonds produced under even (not gradient) temperature conditions will likely become the most important type of gem-quality synthetic diamonds in the future.

In presentations on gem corundum, Anette Juul-Nielsen (Ministry of Mineral Resources, Nuuk, Greenland) provided an update on small-scale mining of rubies and pink sapphires near Fiskenaesset, Greenland. She reported a significant increase in the number of small-scale licences issued, although most activities are focusing on prospecting rather than production at this early stage. Dr Jayshree Panjikar and Aatish Panjikar investigated the cause of asterism in star ruby from Neriya, Karnataka, India. They attributed the asterism to the presence of rutile needles in addition to micro-inclusions of tialite ([Al.sub.2] Ti[O.sub.5], identified by Raman spectroscopy in hazy areas of the gems). Kentaro Emori and Dr Hiroshi Kitawaki (Central Gem Laboratory, Tokyo, Japan) reported on the geographic origin determination of ruby and blue sapphire based on trace-element analysis using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) data in three-dimensional plots. Due to some overlap between localities, they found that such data can help with origin determination but that more analyses are needed from samples of known provenance. Dr Stefanos Karampelas (Gubelin Gem Lab, Lucerne, Switzerland) discussed recent research on zircon inclusions in blue sapphires done by Emilie Elmaleh (University of Geneva, Switzerland) and their co-authors. Potentially locality-specific characteristics of the zircon inclusions consist of cathodoluminescence zoning features and U-Pb age data, but more research is needed before they can be applied to the origin determination of sapphire. Dr J. C. (Hanco) Zwaan (Netherlands Gemmological Laboratory, Leiden) and co-authors performed inclusion and LA-ICP-MS trace-element studies of alluvial sapphires from Montana, USA. Both the inclusion suite and a plot of Fe vs. Ga/Mg supported a metasomatic origin for these sapphires. E. Gamini Zoysa (Institute of Gemmological Sciences, Colombo, Sri Lanka) reviewed sapphire deposits of Sri Lanka. He described recent mining at Wellawaya for in-situ corundum, at Getahetta for sapphire 'geodes', at Bogawantalawa for large opaque corundum crystals, and overall gem production from Hasalaka, Elahara and Kolonna. Dr Karl Schmetzer (Petershausen, Germany) and co-authors reported on dual-colour double stars in corundum and quartz; these results were recently published in Gems & Gemology (Vol. 51, No. 2, 2015, pp. 112-143). Dr Visut Pisutha-Arnond and co-authors (Gem and Jewelry Institute of Thailand, Bangkok) performed Be-diffusion experiments on sapphires under reducing and oxidizing conditions. Trapped-hole centres that formed during oxidative heating were inactivated by heating in a reducing atmosphere, and therefore the resulting colour was solely controlled by the Mg/Ti ratio in the sapphires. Further heating under oxidizing conditions reactivated the Be-induced trapped-hole centres. Dr Walter A. Balmer (Swiss Gemmological Institute SSEF, Basel, and Chulalongkorn University, Bangkok, Thailand) and Dr Michael S. Krzemnicki provided preliminary results of using Fourier-transform infrared (FTIR) spectroscopy to detect Be diffusion in corundum. The presence of a weak band at 2490 [cm.sup.-1] appears to indicate that a sample was Be diffused, but the absence of this peak is inconclusive. Dr Pornsawat Wathanakul (Gem and Jewelry Institute of Thailand, Bangkok) presented the results of an investigation by Thanong Leelawatanasuk and other co-authors on 'surface de-leaded' glass-filled ruby. Lead was reportedly removed from the glass filling near the surface of these stones so that the treatment would be more resistant to the heat of a jeweller's torch. The examined samples showed features consistent with typical glass-filled rubies. Energy-dispersive X-ray fluorescence (EDXRF) spectroscopy of the stones' surfaces appeared to show less Pb than typical glassfilled rubies, but more data is needed since the Pb content recorded by this technique is dependent on the overall amount of glass-filled fractures in the area analysed, as well as on the amount of Pb in the glass. Using photoluminescence spectroscopy, Dr Ahmadjan Abduriyim (Gemological Institute of America [GIA], Tokyo Laboratory, Japan) examined the residual pressure distribution of mineral inclusions in sapphires from New England, New South Wales, Australia. The pressure surrounding the inclusions was visualized and quantified, but the technique is only applicable to unheated sapphires and inferring the original crystallization conditions is not possible due to annealing that occurred during magmatic transport of the sapphires to the earth's surface. This author reported on mining methods for ruby and other gems in primary and secondary deposits near Mogok, Myanmar (see Gem Notes on pp. 387-390 of The Journal Vol. 34, No. 5, 2015).

In other coloured stone topics, Dr Edward Liu (Gemmological Association of Hong Kong) and coauthors used variable pressure-scanning electron microscopy-energy dispersive spectroscopy and backscattered electron imaging coupled with a Raman spectroscopy system to perform non-destructive insitu chemical and structural analyses of jadeite (fei cui). The technique was useful for differentiating areas of jadeite and omphacite within compositionally and texturally zoned samples. Prof. Mimi C. M. Ou Yang (Hong Kong Institute of Gemmology) and coauthors described the texture of jadeite (fei cui). Using cathodoluminescence and microscopic observation of petrographic thin sections, various jadeite varieties could be correlated to different textures according to their grain size and the granoblastic or porphyroblastic size distribution of their mineral constituents. Shane F. McClure (GIA Laboratory, Carlsbad, California, USA) described the mining, cutting and gemmological properties of emeralds from the Belmont mine in Brazil. He witnessed the faceting of an unusually large piece of rough (29.8 g) into a fine rectangular stepcut gem weighing 18.17 ct (together with numerous small stones) that was set into a custom diamond ring. Masaki Furuya (Japan Germany Gemmological Laboratory, Kofu, Japan) and Scott Davies studied the gemmological features of pallasitic peridot from six different meteorites (Admire, Brahin, Esquel, Fukang, Jepara and Seymchan). Peridot from two of the meteorites, Jepara and Seymchan, contained inclusions that were distinctive enough to identify their host bodies. Using a combination of trace-element analysis and FTIR and ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy, the meteoritic origin of the various samples could be determined in some cases. Peridot from Esquel and Fukang were the most difficult to separate, and those meteorites may have come from the same origin in space. Roman Serov and co-authors (all from the Gemological Center, Lomonosov Moscow State University, Russia) examined the colour origin of Russian demantoid using heating experiments. The optimal heating conditions (up to 650[degrees]C in reducing conditions) modified the intensity of the 430 nm cutoff in the UV-Vis spectra, resulting in a less brown and more green coloration; this suggested that the colour was caused by intervalence charge transfer between [Fe.sup.2+] and [Ti.sup.4+] or involving [Fe.sup.3+]. Dr Andy H. Shen and co-authors (all from China University of Geosciences, Wuhan) reported on the country-of-origin determination of nephrite jade from East Asia. They developed a statistical method (iterative binary linear discriminant analysis) to process large amounts of trace-element data generated by LA-ICP-MS analyses. Using 22 elements, they were successful in separating samples from eight localities to a high degree of confidence. Karen E. Fox (Waterloo, Ontario, Canada) reported on recent visits to Australian opal deposits at Lightening Ridge, Yowah and Coober Pedy, and also discussed opal's stability to crazing. Dr Emmanuel Fritsch (Institut des Materiaux Jean Rouxel and University of Nantes, France) and co-authors described green-luminescing hyalite opal from Zacatecas, Mexico (see article on pp. 490-508 of The Journal Vol. 34, No. 6, 2015). Dr Ulrich Henn (German Gemmological Association, Idar-Oberstein) reported the properties of some rare gem materials: wurtzite from Merelani, Tanzania; mosandrite from the Kola Peninsula, Russia (see Gem Note on pp. 565-566 of this issue of The Journal); and buchite from Eifel, Germany (see Gem Note on pp. 562-563 of this issue of The Journal). Dr Claudio C. Milisenda (German Gemmological Association, IdarOberstein) and co-authors examined some gemstones with photochromism: hackmanite, tugtupite and scapolite. The interesting colour behaviour of these gems is due to S- ions. Dr Dietmar Schwarz (Asian Institute of Gemological Sciences Lab Co. Ltd., Bangkok, Thailand) gave an overview of mines and markets for coloured gemstones. He indicated that East Africa is the most promising area for coloured stone production, and some recent trends in the industry include involvement by large mining companies and the importance of ethical mining and marketing.

Several talks focused on pearls. Prof. Dr Henry A. Hanni gave a presentation for Dr Michael S. Krzemnicki (both from the Swiss Gemmological Institute SSEF, Basel) and co-authors on the imaging of pearls using X-ray phase contrast and X-ray scattering. X-ray analysis with a grating interferometer allows for simultaneous measurement of conventional X-ray absorption, refraction (phase contrast) and scattering, with improved sensitivity to light materials such as soft tissue. The procedure is fast (seconds to minutes) and may be used to analyse an entire necklace at once. Using known natural and non-bead-cultured Pinctada maxima pearls, Nick Sturman (GIA Laboratory, Bangkok, Thailand) and co-authors illustrated several examples showing the challenges of correctly interpreting structures seen using X-ray computed microtomography. Sutas Singbamroong (Dubai Central Laboratory, United Arab Emirates) and co-authors presented observations of natural non-nacreous pearls reportedly from various Tridacna clam species. Observations of a large collection of these pearls showed that they were mostly white (some had yellow areas) and semi-translucent to opaque with chalky blue long-wave UV fluorescence. Many had well-developed flame structures that sometimes showed iridescence. SG values typically ranged from 2.81 to 2.85, although some had significantly lower values of 2.63-2.67. X-radiography commonly revealed no internal features, or only dark areas (probably organic material) in the core of those that had the lower SG values. Dr Jayshree Panjikar gave a presentation for Elisabeth Strack (Gemmologisches Institut Hamburg, Germany) on freshwater pearls from Wisconsin, USA. These pearls were gathered from the 1930s until 1996 (when pearl fishing was banned) and are found in local museums and private collections, in addition to being available from a few local dealers. They are typically white (less commonly pink, purple, blue or green) and range up to 15+ mm, with baroque shapes being most common.

There were two presentations related to instrumentation. Dr Lutz Nasdala (University of Vienna, Austria) and co-authors described the search for appropriate gem zircon samples to use as an analytical reference material for age dating using ion microprobes. Large cut gemstones from Ratnapura, Sri Lanka, have shown good potential for such reference material. Manfred Eickhorst (System Eickhorst, Hamburg, Germany) recounted technical progress on the use of light-emitting diodes (LEDs) in gemmological instruments. The main benefits of LED lighting are that it is cool to the touch and has versatility with regards to spot vs. diffused beam types and colour temperature/ wavelength (from daylight to long-wave UV).

Poster presentations covered diverse topics. Gagan Choudhary (Gem Testing Laboratory, Jaipur, India) described emeralds from Jharkhand State, India, which are unusual for being free of any fluid inclusions. Helmut Pristacz (University of Vienna, Austria, and University of Tokyo, Japan) and coauthors studied synthetic turquoise from the Natural History Museum in Vienna, Austria, and found that it had an oolitic microstructure composed of a fibrous amorphous phase (related to the high-pressure berlinite structure) together with natural turquoise (presumably used as a starting material) and synthetic turquoise. Antonello Donini and co-authors (all from CISGEM Laboratory--Fondazione Gemmologica Italiana, Milan) described some unusual gemmological materials seen in their laboratory, including several ornamental objects made from rhinoceros horn and a necklace composed of ambergris (an intestinal secretion produced by sperm whales). Dr Emmanuel Fritsch and Joel Ivey characterized 'Mustard Jasper' or 'Bumble Bee Stone' from western Java, Indonesia, which consists of calcite that is coloured yellow to orange by inclusions of pararealgar and realgar (both polymorphs of [As.sub.4][S.sub.4]) and black by pyrite impurities. Dr John M. Saul (Oryx, Paris, France) examined the historical use of the word electrum for both amber and for the naturally occurring alloy of gold and silver. Dr Guanghai Shi (China University of Geoscience, Beijing) and co-authors examined the infrared spectral characteristics of amber from three sources: the Baltic Sea, Dominican Republic and Myanmar. Transmission spectra were obtained by specular reflection using the KBr pellet method, and could be correlated with the ambers' age, plant provenance and geological environment. Elizabeth Su (Gemsu Rona, Shanghai, China) described jadeite markets in China, including wholesale outlets in Guangdong Province (Yangmei, Guangzhou, Pingzhou and Sihui) and Yunnan Province (Ruili, Tengchong and Kunming), as well as retail markets in Beijing and Shanghai. Thanong Leelawatanasuk and co-authors (all from The Gem and Jewelry Institute of Thailand, Bangkok) provided an update on their studies of treated 'black' sapphires that appeared in late 2013 and mid-2014. The very dark blue body colour of these gems resulted from the Ti-diffusion treatment of heavily fractured starting material of metamorphic origin. Supparat Promwongnan and co-authors (all from The Gem and Jewelry Institute of Thailand, Bangkok) described a synthetic ruby overgrowth on natural corundum encountered in early January 2015. Such material was circulated in the market in the early 2000s and sold under the misleading name 'diffusion ruby'. It can be identified by a sharp contact boundary between the core and the overgrowth seen under immersion, as well as contrasting fluorescence behaviour shown with the DiamondView.

This author also attended the post-conference field trip, which visited amber museums (e.g. Figure 2) and an amber-processing facility in Lithuania (to be reported in the next issue of The Journal).
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Author:Laurs, Brendan M.
Publication:The Journal of Gemmology
Article Type:Conference notes
Geographic Code:4EXLT
Date:Sep 1, 2015
Words:2772
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