This important new encyclopedia is a milestone in lapidary publishing. It is the first reference source to present data on every known species and variety of gemstone. Furthermore, its rich selection of color photographs shows more species than have ever before appeared in one volume.

You can easily find the data you need to identify any gemstone. 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, lustre, 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. For as many as 100 of the rarer species a color photograph appears for the first time in print.

Arem’s transparencies represent today’s most sophisticated techniques for gem photography. Resulting from his own three year effort, they show the exact color of faceted gemstones while displaying to best advantage the cut and brilliance derived from the cutting. At the same time hot spots or specular reflections from individual facets are avoided. The photos achieve naturalistic solidity and dimension, in many cases clearly revealing the degree of birefringence in a gem as well as any inclusions. Some of the data provided have never been published before, such as the dispersion values for 15 gem materials. These values are calculated from material scattered throughout mineralogical literature, and reworked to make them useful for gemologists

Of practical interest to gem cutters is a special graph relating critical angle and refractive index. Other books list critical angles for various gems, but because of the wide range in optical properties in certain gem species these numbers are not always valid. The graph included here makes it possible to determine the exact critical angle to use for the specific material to be cut.

With the growing interest in the investment potential of gemstones, the lay public can also consult this versatile reference for information or photographs  before making a decision to purchase. Collector s of gems, especially connoisseurs, will view the unique color plates of many exotic gem species with special pleasure.