The International Gem-mological Conference (IGC) meets in a different country every two years. Those who attend do so by invitation only, and comprise the world’s top gemological experts representing more than 30 COUNTRIES. For the first time, in 1995, Thailand was honored to organize and host the Conference and the Asian Institute of gemological Sciences and carried out this national responsibility through its IGC members Henry Ho and Ken Scarratt.
More than 120 experts, observers and guests, gathered at the Jewelry trade Center for the opening ceremony on October 21, which was marked with video and slide presentations. This was followed by a “Welcome to Thailand” dinner which was hosted by Mr. WK Ho.
The members of the conference then moved to the Rayong Resort Hotel for five days of intensive discussions, presentations, and poster sessions. The poster sessions included details of new gems and new gem deposits, a new gemological spectrophotometer was on view as well as an imaging spectrometer, and a Raman spectrometer.
Before the first presentation a blessing ceremony took place during which each member was given a blessed jade image of Buddha.
The following is a report on some of the presentations given:
Monday October 23
Dereppe and Moreaux: Recent Applications of NMR to the Study of Gemstones.
M. Dereppe explained the basic principals of Nuclear Magnetic Resonance, which is a relatively unknown area within gemological research, to the Conference. He then outlined possible applications, including: natural vs synthetic gemstone identification; the characterization of fluid inclusions; Magnetic resonance Imaging; and the application of “artificial Intelligence’. He concluded that Nuclear Magnetic Resonance provides additional information for the discrimination between natural and synthetic stones and opens new perspectives for the non destructive investigation of fluid inclusions.
Lasnier, Talay, and Lefrant; A New Portable Raman Spectrometer for Industrial Applications Especially Adapted to gemological Characterizations.
Bernard Lasnier described a soon-to-be-available new portable Raman spectrometer. The unit will measure 43 x 34 x 17 cm and weigh 15 kg. The battery provides for 4.5 hours of continuous operation, the spectral range being 400-1100 nm. The resolution is said to be 0.1 nm, and exposure times from 0.877 msec to 67.1 sec. Apart from Raman operations the unit will also be capable of %transmittance, %reflectance, absorbance, and fluorescence applications. It will also have complete colorimetry applications combined with high quality real-time graphics.
Nelson: Identification of Subsurface Inclusions with Raman Spectroscopy.
Jamie Nelson described how he became convinced that Raman Spectroscopy was the “True Faith” and the “most remarkable tool” following his visit with Dr David Smith of the Museum Hisorique le Natural in Paris. He further pursued the topic with the firm of Renishaw in the UK, and over the previous 18 months has collected, along with AIGS in Bangkok, some 150 characteristic spectra.
DuToit: Raman Spectroscopy and its Usefulness in Identifying Various Internal Features in Gemstones.
Garry DuToit described the Raman unit that is used within the AIGS Gemstone Identification, Grading and Research Laboratory, to determine the nature of host materials, as well as inclusions. He then showed a series of spectra and the inclusions they describe as being examples of the increasing databank that was being compiled within the AIGA Laboratory.
Harding: The Brewster Angle Meter
Following an historic perspective, Roger Harding described a new prototype Brewster Angle Meter that was being developed by Peter Read and tested by himself. In 1993 an experimental model was demonstrated which used the body of a Rayner Dialdex Refractometer and was fitted with a 4mW 670 nm miniature solid state laser. The Dialdex knob was used to pivot the laser. For safety the laser was only activated when a black light shield was placed over the laser. In 1994 a re-engineered version was produced in which the scale has been calibrated from 1.40-2.10. Even strontium titanate, whose RI in sodium light is the same as that of diamond, can be separated from diamond on this instrument because in the 670nm red light it gives a reading of just over 2.3.
Sutherland, Coenraads, and Webb: Ruby from the Barrington Volcanic Field, East Australia Implications for the Thai Ruby Sources
Lin Sutherland dedicated his presentation to the memory of Prof. Henry Meyer who died earlier this year. He described the rubies in the Barrington basalt field, about 200 kilometers north of Sydney, Australia, stating that the first ruby to be identified had probably been that studied by Geoff Tombs in 1968. He described some fascinating mineral aggregates containing ruby, and sapphirine, coming from this locality. The rubies have been brought to the surface through a series of eruptions. Some eruptions have been dated as 60 million years and others as young at 4 million years.
Zoysa and Zwaan: Colorless and Yellowish Scapolites from New Discoveries in Sri Lanka.
Gamini Zoysa described two deposits of scapolite from Sri Lanka, one at Pohorabwa producing gem quality material of up to 20 grams, and the other at Embilipitiya. The material can be distinguished from other yellowish gemstones in Sri Lanka by its strong orange-yellow to canary yellow fluorescence under long-wave ultra violet light, and by their greater amount of double refraction.
Henn: Gem Quality garnets from Mali
Ulrich Henn described the garnets from the Western African State of Mali that have been available since 1994. The occurrence is in the south western part of Mali and about 30 km northwest of the capital, Bamako. Faceted stones of up to 25cts is weight may be obtained but such stones are rare. RI’s and SG’s aren=1.751-1.788 and 3.58-3.73 respectively. Indicating that they are members of the grossular-andradite solid solution series. The RI’s are in direct correlation with the Fe2O3 content. The colors range from fine yellowish to brownish and green to emerald green.
Hanni, Krzemnicki. Kiefert, Schmetzer, and Bernhardt: The Deposit and Sapphires from Southern Madagascar.
Henry Hanni described the sapphires from this new and interesting source. The crystals are usually small measuring 5-15mm across, and are of a light to a dark blue color with the shapes being varied. Inclusions identified are apatite, calcite, spinel, diaspore, CO2, and rutile.
Tuesday October 24
Osipowiez, Tay, Tang, and Watt: Nuclear Microscopy on Ruby
Tay Thye Sun outlined his experiments with nuclear microscopy that had an objective of analyzing trace elements, and inclusions, in rubies from Burma and Thailand. He concluded by stating that, although this was an expensive technique it is very sensitive and non-destructive. The good thing about nuclear microscopy is that it is a powerful analytical tool where PIXE and RBS were used simultaneously to analyse inclusions and give information on the overall picture of the elemental composition and structure of the sample.
Schmetzer: Russian Flux Grown synthetic Alexandrite.
Karl Schmetzer discussed a project on which he was working that involved the examination of about 200 crystals of synthetic alexandrite. Some of the crystals were from the original 1980-1982 development period in Novosibirsk while other were more recent productions obtained in 1993 and 1994.
Cyclic twinning was revealed in 90% of the crystals. XRF analysis revealed minor amounts of Cr, Fe, sometimes V, Ge, Bi, and Mo. Bi and Mo being from the flux used in the growth process. Most surprising was the distinct presence of Ge which had not been previously reported. Characteristic growth features were also discussed.
Arps and Zwaan: Green Beryl and Emerald from Central Nigeria
Charles Arps described an investigation of 170 pieces of beryl he selected from 1000 crystals and crystal fragments, in addition to 20 cut stones. The specimens were documented for crystal habit, growth phenomena, inclusions, physical properties, color, and chemical composition. The beryl’s had been recovered from primitive open cast mining in central Nigeria. SG’s varied between 2.672 and 2.686 and RI is between 1.560-1.565 and 1.567-1.572. Chemical analysis revealed the presence of chromium and iron, as well as vanadium.
Bosshart – Sapphires and Rubies from Laos
George Bosshart firstly related some of the historic aspects of sapphires and rubies from Laos. He then described how, in September of 1994, he was offered the opportunity to examine a large lot of unheated material while he was on a visit to Bangkok. He then went on to describe the whereabouts of the deposits, and the various characteristics of the material, including absorption data and inclusions.
Chikayama: Gemstones of China II
Prof. Chikayama described 41 new gem deposits in China. The gems described included, rhodonite, serpentine, quartzite, saussurite, turquoise, malachite, ammonite, lepidolite, jasper, dolomite, smithsonite, cinnabar, diamond, ruby, sapphire, emerald, aquamarine, topaz, peridot, tourmaline, zircon, garnet, fluorite, and amethyst.
Pough: Red Beryls
Dr. Pough related how Utah’ gem rich rocks are rhyolite and that the red beryls occur in seams within the Wah Wah mountains. He stated that after a day of collecting, with some good luck you can end up with a nice collection of crystals. The occurrence is unique and therefore from the commercial standpoint the red beryl is a product that is easily controlled. The largest cut stone is 7.00ct, although this is exceptional as most sizes are fairly small.
Schwarz: Mineralogical Aspects of Emerald Genesis
Dietmar Schwartz informed the conference on several aspects of the genesis of emerald. Covering the classification of beryl/emerald deposits from an historical aspect, and then explaining criteria for a new classification of emerald deposits. This included both geologic-geochemical criteria and mineralogical criteria.
Arps: Tektites: Their Origin, Properties and Use.
Charles Arps described Tektites as relatively small shiny black to dark brown of green, partly transparent natural glass objects with characteristic but variable shapes, symmetry and surface morphology. He also stated that they occur in four geographically restricted areas on earth-strewnfields. (1) Southeast Asia and Australia, (2) Czechia in central Europe, (3) lvory Coast in West Africa, and (4) South to Southeastern North America.
Wednesday October 25
Saul: “Electrum” in Antiquity: Why was one word used for two substances?
John Saul presented a paper that questioned why in former times the word “electrum” designated two substances which to us today are very different, i.e. amber and the alloy of gold and silver. He related his investigations into the myths, and questioned the period when it might have been realized that “gem” and “metals” were different.
Levinson: Diamond Economics-Selected Aspects
Prof. Levinson related that at the Paris Conference the last slides he had shown were those of the new Canadian diamond deposits. He then indicated that in about four years approximately 2-3 million carats per year of rough diamond should be available to the market, from the Northwest Territories of Canada. He then described several selected historic trends in the diamond industry and concluded that over the last century the diamond industry, particularly the production and retail segments, has undergone significant changes that are likely to continue, especially if major new deposits, in additional countries, are found.
Bouquillon, Mossmann, Querre, and Poirot: Achamenid Treasure of Suse
Jean-Paul Poirot described a great necklace with four strings of beads in gemstones and gold and smaller necklace with one string, and several other items including buttons, bracelets, and a torque. These items being found in a kingly achemenid sepulcher (4th century BC) found during excavations conducted by C. Morgan in 1901. He examined the materials by optical methods as well as PIXE analysis on AGLAE. Stones identified included lapis lazuli and carnelians, and an open bracelet was determined to contain 90% gold, 5% silver, and 5% copper.
Sevdermish: The Effect of Heat Treatment on Tanzanite
Mr. Sevdermish related his detailed experiences concerning the heat treatment of tanzanite.
Hanni: Tanzanite
Henry Hanni gave the conference an abstract of the work carried out on Tanzanite by one of his students at Basel University. A large number of crystals and faceted zoisites were examined by spectroscopy and for chemistry by both EDXRF and microprobe.
Thirmongkol: The Influence of the Environment on Heat Treatment of Corundum.
Varunee Thiramongkol stated that whilst it is generally understood that temperature is a prime parameter for the treatment of corundum. The environment also plays an important role. Among the many examples given it was stated that rubies from Mong Hsu, Africa and Trat when heated in an oxidizing atmosphere produced a purer red color, whereas if they were heated in a reducing atmosphere their purple color is increased.
Zecchini: Taille Brilliant
Prof. Zecchini demonstrated a video of the brilliant cut and how it interacts with light depending upon shape and the refractive index of the material.
Sapalski: The Guarrazar Treasure Study of Gemological Materials
After 137 years since their discovery, the first detailed gemological examination of the Guarrazar Treasure has been carried out. The details were revealed to the conference by Cristina Sapalski as follows: the treasure contains: 260 blue sapphires; 3 cordierites; 13 emeralds; 1 aquamarine; 2 moonstones; 12 amethysts; 8 rock crystals; 5 chalcedonies; 170 pearls; 155 pieces of mother of pearl; 56 pieces of green glass; 26 pieces of blue glass; and 2 pieces of orange glass.
Graziani: Gems from Excavations of Crypta Balbi (Rome)
Prof. Graziani described the Crypta Balbi, its history and location and then 28 samples of gemological interest found within. Most of the samples were of a decorative nature however both beryl and sapphire were described as being present. Normal gemological tests were carried out, together with infra-red spectroscopy.
Payette: Natural Freshwater Pearls from Lac St Jean Area.
Francine Payette described the mollusk and the pearls produced in Lac St jean, Quebec, Canada. The mollusk is Magaritifera, which has an oval shape and can reach approximately 15x6.5x4 cm. Analysis of the pearls was carried out by visual observations, cathodoluminescence, x-ray diffraction, and SEM. The main component of the pearls was found to be aragonite.
Brown: Some Unusual Pearls
Grahame Brown described some interesting unusual pearls that he has examined over the years. These included, edible oyster pearls, hammer oyster pearls, wing shell pearl, clam pearls, coconut pearls, cephalopod pearls, and other pearls from abalone, pink conch, baler, troches, turban, helmet, rainbow limpet, periwinkle, murex, and sacred chank.
Piat: A Few Slides Recently Taken at the Emerald Deposit in Afghanistan.
M. Piat described the Afghanistan emerald deposit as being in the Panj-Shir valley northeast of Kabul. The slides used were taken by Prof. Shwartz on a recent visit.
Thursday October 26
Koivula: New and Unusual Inclusions
John Koivula captured the interest of the conference with a catalog of the new and unusual inclusions he had observed. He opened with photomicrographs of inclusions in amber including a spider with its web in which were trapped insects. Other items included sapphirine in iolite, spinal in hessonite, and inclusions that look like train tracks in spinal from Vietnam.
Ouyang: Comparable Aging Studies on Chemically Treated Jadeite (Type B) and Natural Jadeite (Type A).
Ms. Ouyang described how she had tested various types of jadeite for aging. The tests carried out included, detergent soaking, temperature, and daylight and ultraviolet exposures. The results of the tests indicated that the interlocking structure of jadeite is “destroyed” by the acid treatment that is the first step of producing “B” jade, and that the stone only holds together by virtue of the added polymers. The polymers may break down in time and therefore it is recommended that care be taken with treated stones, particularly during washing.
Shida: Fingerprint of natural diamonds, observations by cathodoluminescence.
Junko Shida outlined the coming importance of the observation of growth defects as not only a method to be used for gemological identification but also in “fingerprinting”. X-ray topography, laser tomography and cathodoluminescence were cited as three possible methods, but only the latter was concentrated upon in this presentation.
Ms. Shida described her cathodoluminescence experiments with various kinds of diamond, including, “D” colors, yellows, orange/browns, green, blue, and pink.
Sunagawa: Fingerprinting of Two Brilliants- X-ray Topographic and Cathodoluminescence Topographic Studies
Prof. Sunagawa cited the problem of trying to identify two parts of a diamond after they had been faceted and gone there separate ways within the diamond pipeline. He showed clearly that the matching of two parts of a diamond can be achieved with a combination of x-ray topography and cathodoluminescence tomography.
Friday October 27
Nelson: New Teaching Aids and simple gemological techniques
Jamie Nelson described the teaching aids he had devised over many years to assist students in understanding the various gemological phenomena. He described a simple cooling unit he had devised for observing the spectra of diamonds which consisted of a vacuum flask though the lid of which he had secured a copper rod. With the lid screwed into position the copper rod is immersed in liquid nitrogen within the flask. The temperature is transferred to the upper part of the rod that emerges in the center and outside of the lid. The diamond is placed in contact with the rod at this point and the spectrum observed with the aid of a specially designed holder for the spectroscope.
Schrauder and Navon: Fluid Inclusions in Diamond
Oded Navon described certain types of diamond in which he had discovered individual inclusions containing multiphase mineral assemblages consisting of carbonates, apatite, a mica mineral, and quartz. Recently they found a new type of fluid baring diamonds, The IR spectrum of a small diamond with octahedral faces and zoned brownish coloration revealed strong absorption due to CO2
Hansawek and Pattawalai: Geological and Gemological Aspects of Kanchanaburi Sapphire
Rak Hansawek described the deposit at Kanchanaburi as Thailand’s main source of sapphire. The deposit is situated approximately 100 km from Bangkok and 40km north of Kanchanaburi town. Basalt is the source rock although mining is mostly alluvial.
Gray: The Role of the Lapidary in Gemological Research
Michael Gray related how the lapidary is usually one of the first people to see gem material from new sources, and as such may be regarded as a huge, and relatively untapped, reservoir of gemological information. He also stated that the independent lapidary is innovative and is often involved in the heat treatment process. When heating one stone he will very often “throw” in some other stone to see what will happen. It was in this way that his father threw in some benitoite scraps and found, contrary to information gained from scientists, they turned orange.
Panjikar, Ramchandran, and Balu: New Emerald Deposits from Southern India
Earlier this year emeralds were discovered in a well in a village in the Salem district in the Tamil Nadu State. Ms. Panjikar described the geology of the area and described the physical and optical properties of the emerald (SG range 2.7-2.73, RI’s as 1.582 to 1.585 “e” ray, and 1.588 to 1.591 for the “o” ray). Other information presented included, spectroscopic data, chemical analysis and microscopic observations.
Jobbins: Interesting Diamonds from the Victoria and Albert Museum in London
Alan Jobbins described a group of diamonds from a collection in London that had thus far gone unreported – the Townshend Collection. One interesting blue diamond recorded the typical infrared spectrum for natural boron colored blue diamond, and measured 9.7-8.7 x 4.5 mm. Interestingly this stone, in common with the Hope Diamond, fluoresces red and phosphoresces red during and after exposure to ultraviolet light.
Superchi, Gambini, and Donini: Recent Observations at the CISGEM Laboratory.
Margherita Superchi related some of the recent observations from the CISGEM laboratory. Specking of natural colored pink fresh water pearls, the usefulness of the Raman technique was cited in recognizing the presence of carotenoids – the cause of color in pink and red pearls and corals. Dr. Superchi went on to describe, stained coral, a new violet jadeite rock, an unusual hydrothermal synthetic emerald, zinc-arsenium artificial glass, and emerald filled with hardened resin.
Atichat: Spectroscopic Approach to Corundum from Chantaburi, Trat, and Kanchanaburi Provinces in Relation to their Genesis
Dr. Atichat described her present research into corundum using FTIR. It was concluded that stones from different localities show characteristic spectra. The spectra are dependent upon (a) the variation in the composition of the sample, (b) the type and number of inclusions, (c) the size and shape of the inclusion, (d) the position of the inclusion (e) the assemblage of all inclusions in the stone (f) the type of location.
Kane: Montana Sapphires
Robert Kane described the four main sapphire mining areas in Montana USA, and followed this with a detailed description of mining methods, production, and processing for the Rock Creek deposit.
Zecchini: Identification of Natural and Artificial Crystallization and Impregnation of Emeralds.
Prof. Zecchini’s study had two principal parts, one was infra-red reflection spectroscopy concerning the differences observed between synthetic and natural emeralds, and also between green beryl and emerald. The other part concerned infra-red transmission spectroscopy in connection with impregnation problems. In conclusion Prof. Zecchini stated that from reflection spectroscopy differention between natural and synthetic emerald could be achieved as well as the separation between emerald and green beryl. For transmission spectroscopy it was possible to confirm the natural and synthetic origin of emerald and identify impregnation techniques.
Atichat: Spectroscopic approach to Corundum from Chantaburi, Trat, and Kanchanaburi Provinces in Relation to their Genesis
Dr. Atichat described her present research into corundum using FTIR. It was concluded that stones from different localities show characteristic spectra. The spectra are dependent upon (a) the variation in the composition of the sample, (b) the type and number of inclusions, (c) the size and shape of the inclusion, (d) the position of the inclusion (e) the assemblage of all inclusions in the stone (f) the type of location.
At the end of the presentation periods the members held a business meeting. The main item on the agenda being the location for the next conference. The members voted for a proposition put forward by Prof. Bank, that the 1997 (26th) International Gemological Conference would be held in Germany. The members then showed their appreciation for the organizers of the 25th Conference. The ending of the formal part of the conference was marked with a dinner the same evening.
On the week-end of October 28 and 29 conference members visited mines and markets in the areas of Bo Rai and Chantaburi, and then flew to Chiang Mai, Chiang Rai, and Mai Sai, visiting cutting factories and gem markets. Some members visited new mining areas in Laos at the same time. Upon return to Bangkok on Friday 3rd November the members visited the sapphire mines of Kanchanaburi.