From Prism Volume III 2023: Map the Mine, Made in Montana, Potentate Mining LLC

By Dr. Keith Barron

Dr. Keith Barron offers a peek into operations at one of America’s most important gemstone mines, the Rock Creek Sapphire Mine in the Sapphire Mountains in Montana.

Hi, friends!

Nature continues to be kind to the Sapphire miners in Montana! The Rock Creek Sapphire deposit in Granite County, Montana, was originally discovered by a gold prospector in 1892. In the early 1900s, Tiffany & Co. was one of the first fine jewelers to incorporate Rock Creek Sapphires in fine jewelry, though many others were shipped to Switzerland for use in the watch industry’s jeweled movements. From 1901 to 1935, only royal blue Sapphires and Rubies were in market demand, though today’s market readily accepts the pastel, teal, parti-color, and colorless Sapphires that Rock Creek has become famous for.

Potentate Mining LLC purchased the first Sapphire property in 2011 and currently owns approximately 3,500 acres of private property covering approximately 90% of the historically known Sapphire-producing ground near Rock Creek in Montana. Since the development of heat-treating technologies in the 1980s and 1990s, Potentate is the first commercial mining operation to market in large volumes to the global gemstone industry.

From Prism Volume III 2023: Map the Mine, Made in Montana, Potentate Mining LLC

Production at the mine site is limited by a short season of approximately six months due to the site’s mountainous elevation, which results in deep winter snowpack and limited water supplies in the summer months. And while we do not process gravels during the freezing winter months, we do operate year-round in the marketing and sales of the production. There is much to be done in the maintenance and repair of the mining equipment, the rehabilitation of the settling ponds, and many other chores. For instance, this last winter our crews acquired a new processing plant in Oregon, and they spent the winter months disassembling and transporting all this equipment from Oregon to Montana.

When it comes to our Sapphires, all those found at the Rock Creek Mine are on or near the surface in alluvial, eluvium, and debris flows caused by the erosion of original host rocks over millions of years. Within these unconsolidated sediments are the heavy minerals, including Sapphires, which are recovered using density separation jigs and centrifugal concentrators. Sapphires are then sorted on light tables in the mine office.

Approximately 80% of our Sapphires are sold within the continental U.S., with the balance being sold to clients in Thailand, Sri Lanka, India, and Europe. Most Sapphires recovered from Rock Creek yield polished gems under one carat in size, with the largest polished stone to date being under 14 carats in size. Approximately 70% of the Sapphire rough Potentate sells is cut overseas in lapidaries in Thailand, India, Sri Lanka, and China; the bulk of our rough is sold to a small group of rough buyers who purchase many kilograms at a time. However, Potentate also exhibits at AGTA GemFair Denver and Tucson to fulfill the demand of smaller-volume buyers and North American lapidaries.

In terms of output, we produced about 100 kilograms of saleable rough Sapphire in our best year and about 40 kilograms in one of our weaker years. Last year’s production was slightly below expectations but comparable to 2021, which was due to mechanical and grade issues. With the commissioning of a new plant in 2023, Potentate anticipates increased production in 2024 to meet strong demand.

Regarding gemstone treatment, some 70% of our Sapphires are heated, which is in line with the global supply of Sapphires on the market today. No other enhancement techniques, such as borax flux, diffusion treatment, or glass infilling, are used.

From Prism Volume III 2023: Map the Mine, Made in Montana, Potentate Mining LLC

Environmentally, our operation adheres to strict standards that do not exist in other Sapphire-producing countries. We rehabilitate all disturbed ground soon after mining by grading the land and reseeding the soils. We use no caustic chemicals in processing, no child labor (of course), pay fair wages by American standards, and recycle over 80% of the water we use so no local fishing environments or creeks are contaminated with pollutants. We also adhere to full disclosure on all gemstone treatments in accordance with the guidelines set forth by the AGTA. Our biggest challenge? Meeting the demands of our clients! But this should be taken care of as we commission our new and much larger plant—until demand catches up with that, too. Everyone loves these gemstones!

We are so devoted to this American-made gem! One of our biggest joys and rewards is seeing our Sapphires in the hands of appreciative clients and collectors. A case in point is a client from last year who cut and polished a few of our Sapphires that took 2022 AGTA Spectrum & Cutting Edge Awards.

Until next time, Keith

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This article first ran in Prism Volume III 2023. See the flipbook by clicking here.