Volume 20, Number 3, July - September 1998

TOURING THE DIAMOND FACTORIES OF AMSTERDAM.

Amanda Barnard FGAA, Dip. DT
Integrated Gemmological Solutions, Melbourne

ABSTRACT
The history of diamond cutting is a varied and intriguing field that is, by its very nature, shrouded in security and secrecy. Amsterdam, 'The City of Diamonds', opens the doors of its diamond factories to hundreds of thousands of tourists every year. Here, not only can one view the exquisite jewels of one of Europe's oldest diamond- producing cities, but one also can watch the 'masters' at work. As this report presents a critique of those tours and facilities offered by seven diamond manufacturers, it is designed to entice and advise those planning a holiday abroad.

THE HODGKINSON METHOD, A.K.A. THE HODGKINSON METHOD: CLARIFYING THE RECORDS

W. Wm. Hanneman PhD
Hanneman Gemological Instruments, Washington. Bretherton

ABSTRACT
Contrary to a previous assertion, the Hodgkinson method is not a "rediscovery". Rather, it is the result of personal experimental observations and the assimilation of phenomena observable since the first gem was faceted. Through his unique grasp of the problems of gemstone identification, Hodgkinson formulated a simple method for confirming the identity of a faceted gemstone without the use of gemmological instruments. To maintain otherwise would rob an innovator of his due.

AMAZONITE IN SRI LANKAN TOPAZ
IDENTIFIED BY RAMAN ANALYSIS

John I. Koivula
Chief Research Gemologist, GIA Gem Trade Laboratory

Shane Elen
Research Gemologist, GIA Research

ABSTRACT
This paper describes the identification of a blue-green crystal of amazonite microcline in a Sri Lankan topaz. The inclusion was identified using laser Raman microspectrometry'. The Raman spectrum of the inclusion was compared to the Raman spectrum obtained from the surface of a polished cabochon of amazonite in GIA's Reference Collection.

GEMS AROUND AUSTRALIA - PART 14

Hylda Bracewell
Brisbane, Australia

ABSTRACT
Why does time always fly so fast when you're having fun? Our visit to Poona, and the Aga Khan emerald mine, was enjoyment and education blended together. Even now, some years later, we look back on the Aga Khan experience as an exceptional interlude in our search for gems.

SYNTHETIC OPAL FROM AUSTRALIA

Grahame Brown
ALLGEM Services, Brisbane

ABSTRACT
A preliminary report on the gemmological characteristics of a new synthetic opal of purported Australian origin.

ON THE IDENTIFICATION OF AMBER AND ITS IMITATIONS
USING RAMAN SPECTROSCOPY
(Preliminary results)

T.S. Tay
Far East Gemological Laboratory, Singapore

Z.X. Shen, S.L. Yee,
Department of Physics, National University of Singapore

ABSTRACT
A total of 173 specimens of amber and its imitations were examined using conventional gemmological methods, followed by Raman spectroscopy. While conventional gem testing methods determined the basic gemmological properties of these organic compounds, the results obtained by Raman spectroscopy seemed to complement these findings. Compared to conventional gemmological testing methods, Raman spectroscopy is fast, non-contact, and non-destructive. Use of a near-infrared laser effectively eliminated the strong fluorescence in the yellow and red that is generated when a laser operating in the visible range excites amber.

TREATED BLUE DIAMOND

Bill Sechos
Gem Studies Laboratory, Sydney

ABSTRACT
A laboratory report describing a glass fracture-filled irradiated greenish blue diamond.

CAT'S-EYE BLACK OPAL

Michael S. White
Atascadero, California

ABSTRACT
A rare cat's-eye black opal from Lightning Ridge, Australia, is described. A hypothesis for the chatoyancy of this opal is presented.