"Written especially for the opal collector and gemmology student, as well as for the opal miner or visitor to the opal fields, this bokk names every recorded opal deposit in Australia and pinpoints every location on concise geologial maps. The text claifies in understandable terms the many mioneralogical, gemmological, and commercial complexities of the opal gemstone and explains the scientific factors involved in opal formation." - book jacket.