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48 www.resourceworld.com J U N E / J U L Y 2 0 1 8 MINING Rubies, emeralds, sapphires, and aquama- rines do not come to mind when thinking of British Columbia, yet the province showcases the complex and diverse geology required to find these rare gems. The demand for all coloured gemstones has increased globally, particularly for those mined in a socially and environmentally responsible manner and an opportunity exists in British Columbia for valuable gem minerals to contribute to the province's economy. Prospectors and exploration companies are well aware of what to look for when exploring for and evaluating metallic and industrial mineral deposits. But coloured gemstone deposits are exceedingly rare. First of all, very few of the 3,800 known mineral species and their varieties have the right mix of beauty, rarity, durability, and history to be considered a valuable gemstone. The second point is that the most valuable coloured gemstones only form under extremely unusual geological and geochemical conditions. For this reason, prolific gem deposits, like in Colombia (emeralds), Sri Lanka (sapphires), and Mozambique (rubies) that are profitable to mine are scarce. Our northern climate and low population is the third consideration when evaluating the gemstone potential of the province. Even the best areas for find - ing gemstones are grossly underexplored. And lastly, many gemstones are difficult to recognize in their rough form and may bear little or no resemblance to what we see in jewelry stores. Many gemstones are routinely treated in some manner to improve their appearance before cutting. A good example is sapphire – plain white, cloudy sapphire crystals may be heat treated to a clear vivid blue. So is it possible to find a significant coloured gemstone deposit in the prov - ince? The answer is yes, going by British Columbia's geological potential and prom- ising initial discoveries made by keen-eyed prospectors and geologists. Beautiful gemstones including star sapphire, iolite, zircon, amethyst, and aquamarine are found in the Passmore Dome metamorphic complex in southeast British Columbia. A prospector made the original discovery in 1991 by recognizing sapphire crystals exposed in an old rail cut near the town of Passmore nestled within the Slocan Valley area. The sapphire crys - tals are dark blue to bronze and display a six-rayed star when cut and polished. Subsequent detailed work by min- ing companies and researchers show the Passmore area exhibits complex geology and an astonishing array of gems within the high-grade metamorphic gneisses. Besides star sapphire, the area produces iolite, which is the lovely pale blue-violet With metallic and industrial minerals traditional targets, BC remains underexplored for gemstones. by Lori Walton, P.Geo., G.G. Coloured gemstone potential in British Columbia A selection of gemstones from the Blu Starr and neighbouring iolite claims near Passmore, BC. Left to right, garnet, iolite, sapphire (back) amethyst (front), garnet and iolite. Photo by Jeff Scovil and courtesy of John Bakus.