[Illustration: Faceted, egg-shaped, 7000-carat rock crystal from Brazil. The gold stand is inset mostly with Montana sapphires. The gem was cut and the stand was designed and constructed by Capt. John Sinkankas of California. (7¼ inches high in all.)] _Gems_ _in the_ SMITHSONIAN INSTITUTION by PAUL E. DESAUTELS _Associate Curator_ Division of Mineralogy WASHINGTON, D. C. 1965 [Illustration: FOR THE INCREASE AND DIFFVSION OF KNOWLEDGE AMONG MEN • SMITHSONIAN INSTITVTION • WASHINGTON 1846] SMITHSONIAN INSTITUTION PUBLICATION No. 4608 LIBRARY OF CONGRESS Card No. 65-60068 CONTENTS The National Gem Collection 1 The Study of Gems 3 The Shaping of Gemstones 10 Gem Substitutes 20 Gem Lore 24 The Principal Gem Species 27 Some Notable Gems in the Collection 70 [Illustration: Prof. F. W. Clarke, former honorary curator of the Division of Mineralogy who assembled the Smithsonian Institution’s first gem collection in 1884.] [Illustration: Dr. Isaac Lea, Philadelphia gem collector whose collection was the nucleus around which the Smithsonian Institution’s gem collection has been built through the years.] [Illustration: Dr. Leander T. Chamberlain, son-in-law of Dr. Isaac Lea, who became honorary curator of the Smithsonian Institution’s gem collection in 1897. Income from his bequest is used to purchase gems for the Isaac Lea gem collection.] 1 THE NATIONAL GEM COLLECTION Man has been using certain mineral species for personal adornment since prehistoric times. However, of the almost 2000 different mineral species, relatively few, perhaps only 100, have been used traditionally as gems. To be used as a gem, a mineral species must have durability as well as beauty. Lack of durability eliminates most minerals as gems, although some relatively fragile gem materials such as opal are prized because of their exceptional beauty. Actually, some gem materials are not minerals at all. Pearl, amber, jet, and coral are formed by living organisms.