Nine faceted Montana rubies from 0.172 to 0.578 ct (figure 1) and seven rough rubies from 0.11 to 0.34 grams, supplied by Mr. To date, only 29 rubies-just over 6 grams-have been found in more than 400 kilograms of mine production. Regardless, rubies from this deposit are extremely rare. Presumably, many rubies had been discarded as garnets in years past. According to Hapeman and Potentate’s Warren Boyd, rubies were only recovered when the miners were asked to put aside anything that resembled a garnet so they could be examined more carefully. Hapeman (Earth’s Treasury, Westtown, Pennsylvania) has amassed a unique collection of true rubies from Potentate Mining’s operation at Montana’s Rock Creek deposit. Over the course of several years, Jeffrey R. (2018) noted the occurrence of rare rubies and violet sapphires from Yogo Gulch (“A common origin for Thai/Cambodian rubies and blue and violet sapphires from Yogo Gulch, Montana, USA?” American Mineralogist, Vol. This journal recently described a ruby submitted to GIA with gemological properties that clearly indicated a Montana origin (Winter 2018 Lab Notes, pp. But what if there is some shred of truth to the old prospectors’ tales? Their vision also may have been clouded by dreams of wealth and hopes of striking a rich gem deposit. He proposes that early prospectors named these sites after stumbling upon garnets and mistaking them for rubies. Voynick provides an explanation for this apparent geographic contradiction. In his epic tome Yogo: The Great American Sapphire (1987), Stephen M. This is surprising given the number of geographic locales in the American West named after the red variety of corundum (i.e., the Ruby Mountains of Nevada and the “Ruby Peaks” found in several states). Kunz, Gems & Precious Stones of North America, Dover Publishing, Mineola, New York, 1968, 367 pp.).
One gap in all of this gemological wealth is the virtual lack of any American ruby sources, with the exception of a minor deposit in North Carolina (G.F. North America has several productive colored stone deposits, from gem tourmaline in Maine and California, to emerald in North Carolina, to peridot, turquoise, and opal in the Western states. Photo by Kevin Schumacher, courtesy of Jeffrey R. The stones range in weight from 0.172 to 0.578 ct.
A suite of nine rubies from the Rock Creek sapphire deposit in Montana. Comprehensive CAD/CAM For Jewelry Certificateįigure 1.
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