Volume 1 provides a short introduction to the formation of gems, and description of various gem materials (including amber, jet, coral, ivory, pearls, tortoise-shell, and synthetic stones). Volume 2 presents a history of gem testing, describes the use and working of a number of special testing instruments, and provides information (in the text and in tables) on technical properties of gems such as specific gravity, light and optical effects, crystal systems, and luminescence. See also AATA (6)-A2-53 and 10-541 for articles on specific test methods. -- AATA