Volume 21, Number 03, July - September 2001

  • Gemstones of Minas Gerais, Brazil

  • Exploration for Diamonds in South Australia

  • The Making of Synthetic Rubies

  • The Gem Emporium in Myanmar

  • An Overview of China's Pearl Industry

  • Notes from the Museum focusing on Travertine

  • Ti-Fe Mineral Inclusions in Star Sapphires from Thailand

  • Macro & Micro Anatase-Rutile Combinations in Quartz

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(Follow this link for abstracts of past issues)

GEMSTONES OF MINAS GERAIS, BRAZIL

I.J. Townsend
Office of Minerals & Energy, PIRSA, Adelaide

ABSTRACT
Description of a field trip to the major gemstone producing mines of Minas Gerais State, Brazil, that followed the 31st International Geological Congress which was held in Rio de Janeiro from 6-17th August 2000.

EXPLORATION FOR DIAMONDS IN SOUTH AUSTRALIA

Dr Kevin Wills
Flinders Diamonds Ltd, Norwood, South Australia

ABSTRACT
A review of the natural occurrence of diamond, and the exploration methods used for the discovery and evaluation of commercial deposits of diamond. The history of diamond exploration in South Australia was described, and the chances of new discoveries of commercial deposits of diamond in that State explained. 

THE MAKING OF SYNTHETIC RUBIES

Dr John Ward
 Adelaide

ABSTRACT
In this presentation the author described his use of an innovative technology - the Electron Beam Gun – to synthesise a polycrystalline mass of ruby of predetermined chemical composition. Synthesised discs of polycrystalline ruby are then annealed in an inert atmosphere to produce crystalline ruby suitable for faceting into attractive synthetic rubies.

THE GEM EMPORIUM IN MYANMAR

A/Professor U Tin Hlaing
 Department of Geology, University of Taunggyi, Myanmar

ABSTRACT
This paper briefly describes the two mechanisms used by the Government of Myanmar to legally sell the jadeite, gemstones, and pearls that are produced in that country. Both Myanmar Gem Enterprise (MGE) and Union of Myanmar Economic Holding Limited (UMEHL) hold periodic Gem Emporiums at which invitees either tender or bid at silent auction for the goods on sale. Differences between the MGE and UMEHL Gems Emporiums are illustrated and explained.

AN OVERVIEW OF CHINA'S PEARL INDUSTRY

Hao Xie, Liping Li
 Gemmological Institute, China University of Geosciences, Wuhan, P R. China

ABSTRACT
In China, pearls were used as ornaments during the Spring and Autumn Period of 770-476 B.C. The Chinese also were the first to learn how to cultivate pearls about 900 years ago. Freshwater pearls were popular during the Qing Dynasty, between 1644 and 1912; but due to social instability that occurred during that time, pearl farming had disappeared as a viable industry by the end of that dynasty. China’s modern pearl cultivation industry began during 1950s to 1960s. Following the adoption of reforming and opening policies for the Chinese economy by Deng Xiaoping, China’s pearl cultivation industry greatly changed. In the 1990s, China’s pearl cultivation industry entered another splendid period. China’s freshwater cultured pearl farms are distributed mainly in Zhejiang Province. Seawater pearl production is presently widely distributed in Guangxi, Guangdong, and the coastal areas of Hainan Provinces. During the 1990s, annual production of pearls reached about 1000 tons. Of this, 20 tons were seawater cultured pearls. China’s pearl cultivation industry has achieved many accomplishments in just over a few decades. China should draw a lesson from Japan’s experience, and avoid similar problems happening to its pearl culturing industry. China’s pearl cultivation industry will have a splendid, very rewarding future.

NOTES FROM THE MUSEUM FOCUSING ON TRAVERTINE

Gayle Webb 
Mineral Section, Australian Museum, Sydney

ABSTRACT
 Travertine is a decorative rock that is often used as a facing stone on buildings, as tiling on floors, as stairs, for furniture, and for other ornamental purposes. It is composed of calcium carbonate, and is a massive crystalline form of the mineral calcite. Travertine has a layered structure, and forms naturally in a range of soft shades that range from cream to golden brown. Travertines are usually opaque, but may grade into translucent varieties that are termed ‘onyx marble’ or ‘stalacmitic calcite’. When examined with the SEM travertine is composed of microscopic crystal that are arranged in miniature forms akin to stalactites, stalacmites, flowstones, and other structures commonly found in caves.

Ti-Fe MINERAL INCLUSIONS IN STAR SAPPHIRES FROM THAILAND

Seriwat Saminpanya PhD, FGA, GG
 Srinakharinwirot University, Bangkok, Thailand.

ABSTRACT
Star sapphires from Bang Kacha, Chanthaburi Province, Thailand, were investigated for their iron and titanium contents with regard to exsolved ‘needles’ and mineral inclusions. The instrument used was the EPMA-WDS (Electron Probe Microanalysis-Wavelength Dispersive Spectrometer), with the techniques of element mapping and spot analyses. The results suggest that the exsolved ‘needles’ are not rutile or hematite as stated in literature. The ‘needles’ are probably a mineral of the ilmenite-hematite series, ilmenite, or a spinel; while other opaque inclusions are magnetite-hercynite. 

MACRO & MICRO ANATASE-RUTILE COMBINATIONS IN QUARTZ

John I. Koivula, Maha Tannous
 Gemological Institute of America, CarIsbad, California, U.S.A.

ABSTRACT
Two interesting variations of anatase-rutile intergrowths are described and illustrated. A combination of optical microscopy, and Raman analysis were used to identify the two separate components. While anatase and rutile are both polymorphs of titanium oxide, they generally occur within distinctly different temperature ranges. Their presence as interconnected inclusions in the same quartz host helps to define that host’s paragenesis, while providing interesting inclusion formations for the collector.