Opal Identification & Value
Downing is eminently qualified to not only write about this colorful gem, but to create this definitive text on opal. --Bob Jones, Rock & Gem Magazine, December, 2002This revision is extraordinarily illuminating and will surely be the definitive work on opal identification, evaluation and valuation for years. --James V. Jolliff, Executive Director, The National Association of Jewelry Appraisers