Volume 21, Number 11, July - September 2003

Volume 21, Number 11  

Geoff Tombs Memorial Issue - Part 1

  • Notes on the Identification of Gilson Synthetic Opal

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  • 35 years On A New Look at Synthetic Opal

  • Australian Gemstones in Memory of Geoff Tombs

  • The History and Importance of Heat Treatment of Australian Sapphire

  • Corundum Conundrum

  • Synthetic-Like Fluorescence in Natural Sapphire

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(Follow this link for abstracts of past issues)

NOTES ON THE IDENTIFICATION OF GILSON SYNTHETIC OPAL

G.A. Tombs
Sydney, NSW

ABSTRACT
Reprint of a 1975 paper in The Australian Gemmologist, by the author, that described the identifying features of newly introduced Gilson synthetic opal.

35 YEARS ON A NEW LOOK AT SYNTHETIC OPAL

Anthony Smallwood
Sutherland, NSW

ABSTRACT
 The 1964 discovery of the structure of precious opal led to a rush among scientists to replicate the material in the laboratory. The CSIRO in Australia was at the forefront of these experiments. About the same time technology for the process associated with the original patent was being investigated in France and the Pierre Gilson Laboratories produced the first truly 'synthetic' opal. This paper reviews the history of those early days of synthetic opal manufacture, as well as examining the more recent production of synthetic and imitation opals from in Japan, Russia, and China. Tables of gemmological constants are provided for comparison with those of natural opal.

AUSTRALIAN GEMSTONES IN MEMORY OF GEOFF TOMBS

Rudy Weber
Sydney, NSW

ABSTRACT
A centrefold photomontage of typical Australian gemstones, which were photographed by the author, and have been contributed to this issue in memory of the late Geoff Tombs.

THE HISTORY AND IMPORTANCE OF HEAT TREATMENT
OF AUSTRALIAN SAPPHIRE

Terry Coldham
Sydney, NSW

ABSTRACT
 The late Geoff Tombs was always interested in heat treatment, publishing several papers on the subject (Tombs 1978, 1979, 1991). However the paper that sticks in my mind the most was written in 1974 and titled 'Synthetic-like fluorescence in a natural sapphire' Tombs 1974. At the time of writing I suspect Geoff probably didn't know his paper had anything to do with heat treatment. In my opinion this paper turned out to be a classic example of just how talented a gemmologist Geoff really was. Just consider the following:

While describing a Fine blue Ceylon sapphire submitted for testing………,, Geoff was surprised by the results he obtained when examining the stone under UV light, summing up his report:

Microscopic examination proved the stone to be natural. This stone is particularly interesting as it is the first natural sapphire I have examined in which blue sections showed fluorescence characteristics exactly the same as those exhibited by the typical Verneuil synthetic blue corundum. The fluorescing areas (under S/W) were curious in that they did not follow the blue colour zoning. (Tombs 1974).

In hindsight I believe Geoff was examining a heat-treated Ceylon blue sapphire a few years before such a treatment became generally known amongst the gemmological community. Most importantly, he recognised that here was something different enough to be worth reporting in his favourite magazine, The Australian Gemmologist.

I dedicate this paper to him.

I would like you to join me in tracing the lives and interests of several people associated with Australian sapphire. They come from widely differing backgrounds and cultures. Some are university educated, while some never went to school. Some are even still alive today. It is through their fascinating testimonies that I have been able to put this story together.

CORUNDUM CONUNDRUM

Boyd Sweeney
Acton Park, Tasmania

ABSTRACT
 An interesting personal story of how a gemmologist with deuteranopuia (colour blindness), learned to cope with his visual difficulty, and discovered but could not see the attractive colour of a rare 2.65 ct rough ruby that he fossicked from in the gravels of Tasmania's Weld River.

SYNTHETIC-LIKE FLUORESCENCE IN NATURAL SAPPHIRE

G.A. Tombs
Sydney, NSW

ABSTRACT
 Reprint of a 1974 paper in The Australian Gemmologist, by the author, that described observation of unusual fluorescence in what was likely one of the early heat treated Sri Lankan blue sapphires.