Volume 20, Number 10, April - June 2000

THE SLOCAN VALLEY SAPPHIRE DEPOSIT NELSON,
BRITISH COLUMBIA, CANADA

Robert R. Coenraads
Consultant Geologist, Queensland Opals N.L., Sydney, Australia.
James W. Laird
2 Geologist, Canadian Sapphire Corporation, Vancouver, Canada

ABSTRACT
The Slocan Valley sapphire occurrence, near Nelson, British Columbia, was discovered by prospector Rod Luchansky in 1991. The property, held by Anglo~Swiss Inc., covers some 45 square kilometres and includes, most significantly, a nine square kilometre, triangular-shaped area of alluvium at the junction of the Slocan and Little Slocan rivers. Corundum crystals have been manually extracted from hard metamorphic rocks collected from outcrops known as Blu Moon and BIu Starr. This process is being undertaken to obtain sufficient material for heat treatment experimentation, and to determine the market value of the treated and cut stone.

The alluvial area remains untested, but it has the exciting potential to yield more valuable and more easily recoverable material than the current hard rock sources.

Other locally found gemstones include garnet, tourmaline, quartz, apatite, and aquamarine, and these may also occur in the alluvial deposit.

PAPERS ON OPAL
previously published in THE AUSTRALIAN GEMMOLOGIST

Editorial Management Committee

ABSTRACT
A tabulation, by issue, page number/s title and author, of all papers on opal previously published in The Australian Gemmologist over the years 1958 to 2000.

NELSON M17 GEMSTONE COOLING UNIT

T. Linton, B. Bretherton
G.A.A. Instrument Evaluation Committee Report

ABSTRACT
Cooling gemstones during spectroscopic examination is a useful technique for revealing identifying VIS spectral features of both natural and treated-colour diamonds, as well as sharpening fine line absorptions found in many coloured gemstones. One of gemmology's everpresent practical problems is how to discriminate synthetic yellow sapphire from natural yellow sapphire ¾ particularly natural coloured yellow sapphire of Queensland origin. This problem can be solved by using low temperatures generated by Nelson Gemmological Instruments M17 Gemstone Cooling Unit to observe the reddish fluorescence of yellow flame fusion synthetic sapphire. This identifying fluorescence is masked by the heat present at room temperature. In addition, use of the Nelson Gemmological Instruments M17 Gemstone Cooling Unit will reveal the relative intensity of free absorption lines in the blue region of the absorption spectra of ruby that can be used to determine the relationship that exists between the c-axis and table of the faceted ruby.

SYNTHETIC FRESNOITE - A NEW GEMSTONE SIMULANT

Dr. Ulrich Henn
German Gemmological Association, ldar-Oberstein

ABSTRACT
Czochralsky-grown synthetic fresnoite [Ba2Ti(Si208)] is being offered as a gemstone simulant on the market. The material crystallizes in the tetragonal system. Refractive indices, birefringence and specific gravity are ne = 1.765, nw= 1.775, Dn = 0.010 and SG = 4.45. Gas 'bubbles' have been observed by using a gemmological microscope.

WHAT'S NEW IN GEM TESTING INSTRUMENTS
THE BREWSTER-ANGLE METER

T. Linton, K. Hunter, A. Cumming (Qld)
N. Masson, G. Pearson (Vic)
G.A.A. Instrument Evaluation Committee Report

ABSTRACT
The Brewster-angle meter uses the beam of a 670 nm laser to measure the angle of incidence at which the polarized reflected ray is at right angles to the ray refracted from a flat facet of a gemstone. This angle of reflection covers gemstones with refractive indices over the range 1.43 to 3.3. The instrument provides readings of Brewster angle, in degrees of rotation of the laser, and not as a measure of refraction or refractive indices. Experience in using this instrument, and precautions when using it, are essential to achieve accuracy.

THE HANNEMAN REFRACTOMETER

T. Linton, K Hunter, A. Cumming (Qld)
G.A.A. Instrument Evaluation Committee Report

ABSTRACT
Dr. W. Wm. Hanneman has taken the Hanneman-Hodgkinson visual optics refractometer two steps closer towards becoming a practical instrument. However, this instrument still requires careful set up and a practical approach to its use. Importantly, it can determine the refractive index of gemstones in the 1.30 to 2.78 range, and so cover the complete range of gemstones without use of toxic refractometer contact fluids.

CAVEAT EMPTOR

Franz H. Thrupp
Moonee Ponds, Victoria

ABSTRACT
This is a cautionary tale about the risks of purchasing inexpensive jade in some Asian countries.

WHERE THE MONSOON COMES EARLIER
The story of a personal journey of discovery

U Tin Hlaing
Geology Department, Taunggyi University, Myanmar

ABSTRACT
A personal story of a journey to Hpakan in search of the famed jadeite (jade) mines of Myanmar. Accompanying the story of this journey is much up-to-date information about the jade mines, their operations, and their product, Burmese jade.