PRECIOUS STONES. 



BY QEORGE F. KUNZ. 



[George F. Kunz, expert in precious stones; born New York, September 29, 1856] siuce 

 1883 has been gem expert of the United States geological survey; was in charge of the 

 department of mines at the Paris Exposition of 1889, and at the World's Columbian 

 Exposition at Chicago in 1893; has been vice president of the American Institute of 

 Mining Engineers ; is now gem expert for Tiffany & Co. Author of Gems and Precious 

 Stones of North America, and of about 150 articles on gems and minerals for maga- 

 zines and reviews.] 



Precious stones derive their value chiefly from their rarity. 

 Other qualities that influence their value are beauty of color, 

 hardness, and the caprice of fashion. Under this classification 

 a distinction could be made between precious and semiprecious 

 stones, but it is not observed in this discussion. Precious 

 stones include the diamond, the sapphire, the ruby, and the 

 emerald; semiprecious stones include a wide variety of other 

 gem minerals. The opal and the pearl are sometimes classed 

 as precious stones, although the latter is not strictly a mineral 

 product. In ordinary speech the precious or semiprecious 

 stone signifies a gem cut or polished for ornamental purposes. 

 In mineralogy the term is used to designate a class of minerals 

 of sufficient hardness to scratch quartz, which are without 

 metallic luster, although generally brilliant and beautiful. In 

 archaeology the term is restricted to engraved stones, such as 

 intaglios and cameos. A jewel is a gem that has been mounted. 



The diamond, the hardest of known substances, is pure 

 carbon, which crystallizes in the isometric system, generally 

 in an octahedral form. Its specific gravity is 3.525. It occurs 

 in a great variety of colors, ranging through all the shades of 

 the spectrum, occurring most frequently as white, yellow, or 

 brown, and rarely as red, rose red, blue, or green. By far the 

 greatest number of diamonds come from South Africa, but they 

 are found also in Brazil, India, Borneo, and occasionally in 

 North America. 



In the United States diamonds have been found at various 

 points, but they have been few in number, and mostly of small 

 size. Their occasional occurrence in California and east of the 

 southern AUeghanies has been known for fifty years. Since 



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