gems, chrysoberyl, alexandrite, phenomena, color-change, zircon, diaspore, tourmaline, usambara effect, Russia, Brazil, Sri Lanka, India, Tanzania, color science

RWH: For those interested in exploring the less-visited corners of gemology, this is one of the best reads out there. It is a collection of articles on color-changing gemstones that is poplulated with wonderful photos and (for a somewhat scientific bent), magnificently circumspect in terms of techno-babble. Highly recommended.