This was the first reference source to present data on EVERY known species and variety of gemstone. And its rich selection of color photographs showed more species than have ever before appeared in one volume.

An alphabetical listing arranges gems according to mineral species. There is also a complete cross index of familiar gem names. Information on each gem includes chemical formula, crystal structure, colors, luster, hardness, density, cleavage, optics, spectral data, luminescence, and sizes. Over 220 mineral species are covered, and the color plates illustrate more than 185 of these – including all known color varieties of each species.