National Geographic : 1951 Nov
© National Geographic Society 645 Kodachrome by Willard It. Culver Digging for Hidden Beauty: A Copper Mine Yields Blue-green Chrysocolla A rockhound chips specimens of the semiprecious mineral (page 650) at the dump of the Inspiration Copper Company, Miami, Arizona. Copper and silica, deposited by underground water filtering through copper ore, form chrysocolla. Pure chrysocolla is too soft for grinding or polishing. Mixed with harder quartz, it forms a beautiful stone often mounted in costume jewelry.