Volume 20, Number 11, July - September 2000

PRESENT RUSSIAN SYNTHETIC AND ENHANCED GEMSTONES

Professor Vladamir S. Balitsky
Institute of Experimental Mineralogy, RAS, Moscow, Russia

ABSTRACT
The former USSR was a major synthesiser of single crystals for defence, scientific and technological purposes. Synthetic gemstones also were used to a great extent in the Soviet jewellery manufactured during that time. Since the USSR split, and started to develop a market economy, more and more technology has been devoted to the production of synthetic gemstones and enhanced gemstones for both the local and export market. This comprehensive report details the range of synthetic and enhanced gemstones produced in today's Russia, the techniques used in their production, where they are produced, and to which countries they are marketed.

DIFFRACTION COLOURS OF OPAL
First spectrometric data

Mikhail Ostrooumov
Metallurgical Institute, University of Michoacan, Michoacan, Mexico
Han A. Talay
Institute of Materials, Laboratory of Crystalline Physics, Nantes, France

ABSTRACT
This paper presents the first spectrophotometric study of the diffraction colours of precious opal. Two types of spectra were obtained from colours diffracted by precious Mexican 'fire' opals by the Hyperfine Analytical Network spectrometer: spectra due to a mixture of diffracted colours, and spectra of pure diffracted colours. The wavelengths of diffracted colours were studied as a function of the diameter of the spheres of silica that form the opal. To characterise the spectra of precious opal, their spectra must be accurately recorded and their colourimetric parameters calculated. It is then possible to obtain a precise objective description of the diffracted colours produced by natural and synthetic opals.

NEW FIND OF GEM QUALITY UVAROVITE IN TIBET

He Xuemei
Gemology Institute, China University of Geoscience, Beijing
Cai Kequin
Vice President, China University of Geoscience, Beijing
Gong Shan
Director, Tibetan Trade Development Co.

ABSTRACT
A deposit of the rare chromiferous green garnet, uvarovite, has been discovered 15 km north-east of the village of Tong Mai in far eastern Tibet. A proportion of the large euhedral crystals of garnet recovered from this deposit can be cabochoned into attractive gemstones. This paper reports the properties of this garnet and hypothesises that the deposit possibly could become the world's first commercial source of gem quality uvarovite garnet sometime in the future.

REFLECTIVITY OF SYNTHETIC MOISSANITE

T. Linton
G.A.A. Instrument Evaluation Committee

ABSTRACT
Following heat treatment the surface of synthetic moissanite becomes coated with a coating that decreases its reflectivity by 59-72 per cent. The nature of this coating will be discussed. Polishing heat-treated surfaces of synthetic moissanite with cerium oxide on leather removed the brownish discoloured layer, but left behind dark spots and 'watermarks'. A warning is offered with respect to the heating of synthetic moissanite.

CHIASTOLITE FROM KYAUSE, MYANMAR

U Tin Hlaing
Department of geology, Tuanggyi University, Myanmar

ABSTRACT
A brief report on the occurrence of gem quality andalusite var. chiastolite in the Kyaukse District of central Myanmar.

UNUSUAL INCLUSIONS IN QUARTZ

John I. Koivula
Gemological Institute of America, Carlsbad, California

ABSTRACT
Large platy masses of the mineral, lithiophilite, as inclusions in quartz are described. While the inclusions yielded a good Raman spectrum, the final identification as lithiophilite was made using X-ray micropowder diffraction and optical microscopy.

PRESIDIUM ^TM MOISSANITE TESTER

T. Linton, K. Hunter
G.A.A. Instrument Evaluation Committee

ABSTRACT
The Presidium Moissanite Tester is a newly marketed instrument that is based on an original concept for testing the 'capacitance' of synthetic moissanite. Beginning with the question "What does this instrument measure (and do) that other synthetic moissanite testers don't?". the Committee attempted to assess the accuracy of this instrument and hypothesise its principle of operation. As a consequence, it would appear that the Presidium Moissanite Tester works by sensing the minute, forward-leakage of current in synthetic moissanite, a known semiconductor.

CHINESE PEARLS: Their culturing and trading

Guo Tao
Director, National gemstone Training Center, Beijing

ABSTRACT
China has a long history of pearl cultivation. In this paper the history of Chinese cultivation of freshwater, akoya and white south Sea pearls will be presented. The present Chinese cultured pearl industry, and its products. Will be described, before details of the international and domestic trade in Chinese cultured pearls will be given.