Volume 20, Number 7, July - September 1999

CHARACTERISATION OF RECENT AND FOSSIL IVORY

Dr Vanda Rolandi GG
Geological & Gemmological Consultant, Milan

ABSTRACT
To identify different types of ivory requires gemmological and structural studies of the material’s taxonomy, visual appearance of cut and polished samples, individual structural characteristics, physical data, infrared and Raman spectra, and X-ray powder diffraction pattern. As some physical properties are common to all types of ivory, sometimes the appearance of its surface under magnification becomes diagnostic. Nevertheless, from a textural standpoint elephant and so-called ‘fossil’ mammoth ivory are remarkably similar. While FT-infrared and Raman spectroscopy may be useful for discriminating recent from ‘fossil’ ivory, biochemical tests have clearly indicated that differences in the amino acidic content of their collagen can be used to discriminate these look-alike ivories.

THE NOMENCLATURE OF GEMSTONES
WITH SPECIAL REFERENCE TO THE GARNET AND
TOURMALINE MINERAL GROUPS

Eric L. Stevens BSc, MSc, MSc, FGAA, FGA
Kallangur, Queensland

ABSTRACT
Gem minerals belonging to the tourmaline and garnet mineral groups are generally assigned names by gemmologists that are technically incorrect. If gemmology is to be an accepted sub-science of mineralogy, then efforts should be made by the disciplines educators to correct the misuse of terminology to achieve accuracy, scientific validity, professionalism, and equally importantly marketing ethics.

RUBY AND VARIOUSLY COLOURED SAPPHIRES
FROM ILAKAKA, MADAGASCAR

Dr. K. Schmetzer
Peterhausen, Germany

ABSTRACT
The gemmological properties of ruby, as well as pink, blue-violet, violet, purple, and orange sapphires from a recently discovered secondary deposit at Ilakaka, Madagascar, are described. The gemstones originate from metamorphic host rocks, and their properties are comparable to those of some of the rubies and sapphires found in the Umba and in the Tunduru-Songea areas of Tanzania.

THE EFFECT OF THE GAMMA-IRRADIATION DOSE COMBINED
WITH HEAT ON THE COLOUR ENHANCEMENT OF COLOURI.ESS QUARTZ

M. V. B. Pinheiro PhD, E S. Lameiras PhD
Centro de Desenvolvimento da Tecnologia Nuclear, Comissão Nacional de Energi Nuclear,
CP. 941, CEP 30123-970, Belo Horizonte, MG, Brasil

K. Krambrock PhD
Dep. de Física, lnstituto de Ciências Exatas, Universidade Federal de Minas Gerais,
CP. 702, CEP 30123-970, Belo Horizonte MG, Brazil

J. Karfunkel PhD
Dep. de Geologia, Instituto de Ciências Geológicas, Universidade Federal de Minas Gerais,
CP. 702, CEP 30123-970, Belo Horizonte MG, Brazil

J.B. da Silva
Pentággono Industrial Exportadora Ltda., Avenida ltaité 835, CEP 30050-550
Belo Horizonte MG, Brazil

ABSTRACT
In this paper we describe experiments that produced several attractive colours from colourless quartz by a combination of gamma irradiation and thermal treatment. For the experiments, colourless quartz containing Fe:Al ratios between 0.13 and 0.32 were irradiated in a conventional cobalt 60 gamma-cell. Following heat treatment, these quartz crystals acquired colours that ranged between green, yellow, orange and brown. The induced colours were a function of the dose of gamma irradiation, and all were stable to natural light.

MONG HSU RUBY REVISITED
Some further data

U Tin Hlaing
Geology Department, Taunggyi University, Myanmar

ABSTRACT
This compilation of new information about Möng Hsu, and its gem quality corundums, should be read in association with Hlaing, U.T. (1993) Möng Hsu ruby update. Australian Gemmologist. 18, 157-160, and Hlaing, U.T. (1995) New extension to the Möng Hsu ruby deposit. Australian Gemmologist. 19, 51.

EKATI
CANADA’S FIRST COMMERCIAL DIAMOND MINE

An editorial review

ABSTRACT
After the year 2000, it is anticipated that the Northwest Territories’ Ekati mine will be producing 4 per cent (by weight) and 6 per cent (by value) of the world's diamonds. This production will come from five kimberlite pipes that are located in the Lac de Gras area some 300 km northeast of Yellowknife. This review will summarise available information on the geology and petrology of these diamondiferous pipes, the history behind development of the world’s newest diamond mine, and the properties and features of what soon will be known in the trade as Ekati diamonds.

TESTER MODEL 590 FOR COLOURLESS MOISSANITE/DIAMOND

An Instrument Evaluation
V.M.E Hammer¹, J. Stefan²

1 Staatliches Edeisteininstitut Naturhistorisches Museum, Vienna
2 Gemmologisches Labor Austria GmbH, Vienna

ABSTRACT
The Staatliches Edelsteininstitut and the Gemmologisches Labor Austria report on the C3 Inc. Tester Model 590 for Colourless Moissanite/Diamond, which was manufactured by C3 Inc. of 3800 Gateway Blvd., Suite 310, Morrisville, NC 27560 USA.