Gems and GemologyGems and Gemology
Home
Saturday, September 6, 2008Printer-Friendly Page
Service Center
Search
My GIA
Back Issue

Summer 1991, Volume 27, Issue 2

Click to Print
Treated Andamooka Matrix Opal
Grahame Brown


Matrix opal from Andamooka, in South Australia, is a precious opal-included porous rock that is commonly color enhanced (carbon impregnated) to imitate the highly prized black opal from Lightning Ridge in northern New South Wales, Australia. This material has been commercially available since the mid-1950s and is often referred to as "sugar treated." A basic sugar acid-carbonizing technique is used to carbonize, and thus darken, the cream-colored matrix of prepolished stones so that the play-of-color is more prominent. The carbon impregnator in treated Andamooka matrix opal can be readily identified with low-power magnification.

Appears on pages 100-106

Back to Table of Contents

Click Here to Buy This Issue or to Subscribe to Gems & Gemology

Home | About GIA | Ethics Helpline | Education | Laboratory | GIA Reports | Research | Instruments & Books | Alumni Association
Gems & Gemology | Employment at GIA | Careers Available | Newsroom | Publications | Library | Events & Trade Shows | Support GIA | GIA History | How to Buy a Diamond
Contact | Search | Site Map | Help
This page was last updated 08/15/05 09:08 AM
Use of this site signifies your agreement to its terms of use.
©2002 - 2008 Gemological Institute of America Inc.
GIA is a nonprofit 501(c)(3) organization.
All rights reserved.
World Headquarters and Robert Mouawad Campus
5345 Armada Drive, Carlsbad, California 92008
Tel: 760-603-4000