John Sinkankas (1915-2002) was a retired United States Navy captain who, after his service, became one of the most respected American gemmologists, lapidary craftsmen and bibliographers of the twentieth century. His combined output as a cutter, mineral collector, writer and book-dealer left a deeper imprint on English-language gem literature than almost any other single figure of his generation.

Life and trade

Born in Paterson, New Jersey, Sinkankas trained as a naval aviator and flew during the Second World War and the Korean War. After retirement from the Navy in 1961 he settled in San Diego, California, where he ran a faceting workshop and, with his wife Marjorie, built Peri Lithon Books into a leading antiquarian dealership in the gem and mineral trades. Cutting was not a sideline. He was an exceptionally skilful faceter who produced large, well-proportioned aquamarines, tourmalines, beryls and quartzes from rough that he often acquired on field trips to Brazil, the United States and elsewhere.

Writings

Sinkankas wrote or edited more than a dozen substantial works. Gemstones of North America (three volumes, 1959, 1976 and 1997) remains the standard reference for the subject. Emerald and Other Beryls (1981) is widely regarded as the most thorough single-volume monograph on the species in English and is still cited by Lotus Gemology and other contemporary laboratories. Gem Cutting: A Lapidary's Manual (1962, second edition 1984) introduced a generation of hobbyists to faceting. Gemology: An Annotated Bibliography (1993), a two-volume work of more than 1,200 pages, mapped the entire field of gem literature from antiquity to the late twentieth century and remains an essential research tool.

Recognition

The Gemological Institute of America awarded Sinkankas its Robert M. Shipley Award in 1979 for distinguished service to the profession. The American Gem Society elected him to honorary life membership. Several gem species and mineral specimens carry his name in collection catalogues, and his personal library, sold through Peri Lithon, seeded many of the major institutional gem-book holdings now held in North America.

Trade significance

For working jewellers and gem dealers Sinkankas matters because he wrote as both a craftsman and a scholar. His descriptions of optical behaviour, cutting orientation and locality were grounded in stones he had personally faceted, and his bibliographic work taught the trade how to evaluate older sources critically. His books are routinely consulted at Skyjems when researching unusual material or assessing historical attributions.