Volume 20, Number 9, January - March 2000

A PRELIMINARY INVESTIGATION OF PRECIOUS OPAL
BY LASER RAMAN SPECTROSCOPY

Anthony Smallwood FGAA, GG
Sydney, New South Wales

ABSTRACT
As gemmology moves into the 21st century, and attempts to keep pace with advances in modern scientific technology, the focus of some gemmological investigations and identifications is moving away from traditional gem testing instruments towards the use of more high-tech instrumentation. Today, gemmology is becoming more and more advanced and of necessity expensive equipments are being used.

This paper will provide an introduction to Raman spectroscopy by illustrating its use in the non-destructive identification of specimens of opal from various sources in Australia, and their discrimination from so-called synthetic opal. In addition, a specialised microscope attached to the Laser Raman spectroscope has been used successfully to identify the type of opal (natural, synthetic, or imitation) used in the manufacture of composite opals. These identifications can be difficult to make using conventional gem testing methods.

DIAMOND PROOVER II

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

ABSTRACT
Increasing availability of synthetic moissanite has resulted in an influx of new and upgraded specific detection instruments into the gemstone and jewellery market. Variations in the principles of operation and basic features of these new gem-testing instruments are producing some confusion among their potential users. In this report the G.A.A's Instrument Evaluation Committee describes a new gem-testing instrument that combines two existing methods of discriminating diamond from its newer imitations, such as synthetic moissanite. BTR Inc. of Park Ridge, New Jersey (USA) have combined a thermal 'conductivity' probe with a surface reflectivity meter to produce the Diamond Proover II for discriminating diamond from its imitations.

IN DEFENSE OF GEMMOLOGISTS
A DIFFERENT VIEW ON NOMENCLATURE

W. Wm. Hanneman
Poulsbo, Washington

ABSTRACT
A response to Stevens, E.L. (1998) Nomenclature of gemstones. Australian Gemmologist. 20, 277-279).

A WARNING
BEWARE OF 1.815 REFRACTOMETER CONTACT FLUID

Trevor Linton, Chairman
The GAA Instrument Evaluation Committee

ABSTRACT
A warning of the potential hazard to health posed by a high [1.815] refractive index refractometer contact fluid that can be purchased over the internet.

CROWN ANGLE ESTIMATION FOR DIAMOND USING A 'TILT TEST'

Garry Holloway
Melbourne, Victoria

ABSTRACT
A description of a method for estimating the crown angle of a brilliant cut diamond by observing the image of its culet through a kite facet as the diamond is gradually tilted about its vertical axis.

GEMS AROUND AUSTRALIA
Part 15

Hylda Bracewell
Brisbane, Queensland

ABSTRACT
There is no doubt that Western Australia is rich in minerals and gemstones, and is especially blessed with a variety of ornamental gem materials. We were extremely fortunate to have visited a great many of these deposits while in Western Australia. Since this trip was undertaken quite some time ago now, it seems fitting that it concludes in this special Australian issue of the journal. Do I hear a sigh of relief from the editor?

THE MERLIN DIAMOND MINING PROJECT
Part 1: An introduction

An editorial review

ABSTRACT
The Merlin Diamond Project is Australia's fourth commercial diamond mining operation after the historic alluvial diamond mining operations in the Copeton and Bingara areas of northern New South Wales, the open cut Argyle mine which is the first and largest diamondiferous lamproite pipe in the world, and the alluvial Bow River diamondiferous gravels to the east and down river of the Argyle pipe. This introduction details the origins of Ashton Mining's Merlin diamond mining project up to its Stage I period of trial mining that is scheduled to last two and a half years to the end of the year 2002.

D-LIMONENE
A USEFUL IMMERSION LIQUID FOR GEMMOLOGY

T. Linton
Wellington Point, Queensland

ABSTRACT
D-limonene is a colourless, non-toxic, citrus flavoured immersion fluid that has many potential uses in gemmology. Some of the important uses of this fluid are described and illustrated in this short paper.

A NEW DEPOSIT
OF
SMOKY QUARTZ CRYSTALS FROM THE TORRINGTON AREA

Hylda Bracewell
Torrington NSW

ABSTRACT
A brief illustrated report of a new find of specimen quality smoky quartz crystals from Silent Grove, north of Torrington in the New England Tableland. A6t Silent Grove, more than 8,000 prismatic crystals of specimen to gem quality were recovered from a small, apparently isolated vugh in 'granite'.

RARE AUSTRALIAN GEMSTONES
STICHTITE

R.S. Bottril¹, G. Brown^2
1. Minerals Resources Tasmania, Rosny Park, Tasmania
². ALLGEM Services, Brisbane.

ABSTRACT
The little known Tasmanian gem mineral, stichtite, which occurs as small rose-pink 'knots' associated with residual chromite grains in serpentine, was first discovered at the Adelaide Proprietary Mine, Dundas. This paper summarises the history of discovery, occurrences, associated minerals, and the gemmological properties of this attractive Australian gemstone.