The U.S. Geological Survey is grateful to the following individuals for their assistance: Harvey E. Belkin, Geologist, Geological Survey, U.S. Department of the Interior, Reston, VA. Gordon T. Austin, “Gem Stones,” _Mineral Commodity Summaries 1991_, Bureau of Mines, U.S. Department of the Interior, Washington, DC. Robert E. Thaden, “Gem Stones,” in _United States Mineral Resources_, Geological Survey Professional Paper 820, U.S. Government Printing Office, Washington, 1973, p. 247-250. Jane Jenness, Minerals Information Office, U.S. Geological Survey, Washington, DC. Photographs All photographs are courtesy of The Smithsonian Institution. Transcriber’s Notes --Retained publication information from the printed edition: this eBook is public-domain in the country of publication. --In the text versions only, text in italics is delimited by _underscores_. --In the ASCII version only, subscripted numbers are preceded by underscore and delimited by brackets. End of the Project Gutenberg EBook of Natural Gemstones, by Various