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Potentate Mining is actively operating on its property in this area. Among all of Montana’s secondary sapphire deposits, Rock Creek has been the most productive. Among Montana’s secondary deposits, Rock Creek (figure 2) is the only area mined specifically for sapphire from its discovery in 1892 until World War II (Clabaugh, 1952).įigure 2. Before the 1940s, the state’s alluvial sapphire deposits were exploited mainly to supply the watch industry, but production fell dramatically with the use of synthetic sapphire in watch bearings (Emmett and Douthit, 1993). Corundum was discovered during the course of gold mining activities in southwestern Montana. Since the latter half of the 19th century, Montana’s history has been intertwined with gold, silver, and copper mining. To better understand the characteristics of Montana sapphire and record current mining and commercial activities, GIA sent a team to visit the placer deposits at the upper Missouri River and Rock Creek areas in August 2015. Today, the first two areas remain quite active, while operations in Yogo Gulch and Dry Cottonwood Creek have been suspended for many years. Historically, gem-quality sapphires have been mined commercially in four main areas in southwestern Montana, shown in figure 1: the upper Missouri River gravel bars (1865), Dry Cottonwood Creek (1889), Rock Creek (1892), and Yogo Gulch (1895). state of Montana for more than a century and a half.
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Sapphire has been mined in the western U.S. Mining at Dry Cottonwood Creek and Yogo Gulch is suspended. Active mining operations are at alluvial deposits along the upper Missouri River and Rock Creek. Sapphire deposits are clustered in southwestern Montana. Comprehensive CAD/CAM For Jewelry Certificateįigure 1.
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