gems, general

A detailed contemporary survey of gem and precious-stone production in 1905, concentrating first on the United States and then on the international diamond industry. American occurrences and mining are reviewed for beryl, garnet, peridot, ruby, sapphire, spodumene, tourmaline, turquoise, and diamond, with particularly extensive accounts of California, Montana, and North Carolina. Notable subjects include the ruby gravels of Cowee Creek, North Carolina; Montana sapphire mining at the Missouri River bars, Rock Creek, and Yogo Gulch; California kunzite and tourmaline deposits; and New Mexico turquoise. The account describes the geology, mining methods, colors and qualities of the stones, important specimens, and commercial prospects of individual deposits. The diamond section discusses reported American occurrences before turning to the industry in South Africa, then overwhelmingly dominant in world production. Production, grades, costs, reserves, and profits are given for the De Beers mines and the Premier mine in the Transvaal. Particular attention is devoted to the recently discovered 3,024¾-carat Cullinan diamond, including its crystal form, cleavage, exceptional colorlessness and transparency, dimensions, and contemporary valuation. Brief accounts cover declining Brazilian diamond exports and production in British Guiana. The article concludes with discussion of the rapidly rising diamond market—reporting a 60% increase in London rough prices over four years—and the newly adopted Elmore oil-concentration process, which was claimed to recover virtually all diamonds while reducing treatment costs and losses.