Books: Smithsonian Nature Guide on Gems
April 17, 2014
The 34-page introduction serves as an overview of gemology, including such topics as gem formation, classification, cutting, enhancements, synthetics, and history and folklore. The book’s only other section, “Gemstones,” includes segments on precious metals and organics and a glossary, but the largest entry is “Cut Stones.” Here, the various gems are arranged much in the style of a mineralogical text, divided by chemical composition. Sections cover the native elements, sulfides, silicates, and tungstates; based on that system, the cut gems are sometimes are presented out of the order anticipated by someone with a working knowledge of Dana’s System of Mineralogy and Dana’s Textbook of Mineralogy. It should also be noted that the book does not further divide the silicates into categories such as soro-silicates or tekto-silicates. For each featured cut gem, precious metal, and organic gem, there is a profile box detailing its basic properties and, where appropriate, the typical cutting styles. The basic chemical formula is given, along with the name origin, formation and source information, and color images, including examples of rough material.
One of the book’s merits is ease of use, with its portable format and easily located vital information. It contains far more gem materials than most comparable books, opening up a whole new world of gems to the consumer. Another virtue is the profusion of color images used to illustrate various aspects of the gemstones. I applaud the “Gem Enhancement” section: To make an informed purchase, the consumer needs to be aware of methods to improve the appearance, durability, and value of a gem material.
Some areas could use revision. The reader is given no sense of the author’s qualifications to write about gemstones. Another issue concerns the use of the outdated terms “precious” and “semi-precious.” Why should the negative connotation of “semi-precious” be applied to such wonderful gems as alexandrite or red spinel, which often sell for at least as much as those traditionally labeled “precious?” I was surprised that beryl, rather than topaz, was used to illustrate a hardness of 8 on the Mohs scale, and disagreed with the assertion that soft stones are cut only for collectors. This may have been true in the past, but with the recent boom in at-home shopping, softer stones such as fluorite are being purchased by a great many consumers. It is important to inform consumers of the care required for softer gems without chasing them away. The color images, while numerous, do not always convey the actual color of the gem. In many of the photos, lines are used to point out a particular aspect of the gem, such as fire or doubling, yet in some instances you can’t see that feature.
Finally, I found some faulty information. The most conspicuous inaccuracy is the statement that flux-melt gemstones, including some synthetic emeralds, leave curved growth zones. The reality is that curved growth zones are mostly associated with flame-fusion synthetics, which do not include synthetic emerald. Flux-melt synthetic emeralds are known for showing angular growth features. There are other inaccuracies of various degrees that could be addressed, but I do not wish to create too negative an impression.
Despite some outmoded terminology and factual errors, this attractive book’s numerous gemstones, helpful illustrations, portability, and low price make it worth purchasing, especially for the general consumer.
Michael T. Evans is senior stones inventory gemologist at GIA in Carlsbad, California, and assistant curator of the Fallbrook (California) Gem and Mineral Museum.