This fascinating text comprises a detailed guide to gemmology, perfect for the aspiring amateur and seasoned practitioner alike. Covering in detail the fundamentals of the subject, this rare book constitutes a great addition to any gemmological collection and is a veritable must-have for those looking for an introduction to the subject. This text is split into the two parts: Transparent Stones and Translucent and Opaque Stones, and contains chapters on: The Materials to be Studied; The "Bending" of light, and its Effects; The Pocket Lens; "Inclusion" in Stones; The "Chelsea" filter; The Microscope; and many more. G. M. Sprague was a fellow, Tully medallist, and Anderson prize-winner of the Gemmological Association of Great Britain. This rare text is proudly republished here with a new introduction to the subject.