Gem News International Gems & Gemology, Winter 2021, Vol. 57, No. 4

Update on Mining Activity at Yogo Gulch, Montana

Underground at the Vortex mine.
Figure 1. Underground operations in the Vortex mine at Yogo Gulch, Montana. Photo by Don Baide.

The Yogo sapphire deposit, discovered more than 100 years ago, has seen renewed mining interest over the last few years. The fame of Yogo sapphires was established in the first few decades the deposit was worked by the London-based New Mine Sapphire Syndicate. Then, a catastrophic flood in 1923 destroyed the mine infrastructure and operations ground to a halt. Production was sparse and unpredictable for the next several decades. Notable events in the modern history of Yogo Gulch include the arrival of Chikara Kunisaki and the Roncor Corporation in 1973, which drilled the 3,000-foot Kunisaki tunnel at the old American mine, and the discovery of a new extension of the sapphire-bearing dike to the west of the deposit, which became the Vortex mine. Since 2017, there has been renewed interest in bringing back large-scale mining operations, and the authors had the chance to observe these activities firsthand in the summer of 2021.

In 2017, Don Baide, a jeweler out of Bozeman, acquired the Vortex mine and started revamping the underground operations to bring the mine back online. In the 1990s, a modern 3,000-foot spiral ramp descending 475 feet was installed at Vortex. Due to years of inactivity, Baide and his miners have had to spend considerable time pumping water out of the underground shafts and rehabilitating the mine, but they are now working through the winter down to the 400-foot level (figure 1). They have uncovered new exposures of the sapphire-bearing dike rock and expect to process ore from this level by the end of 2021.

Bulk of the sapphire deposit is on the Roncor property.
Figure 2. A large portion of the Roncor property is home to the Gadsden house (lower left) and the eastern portion of the Yogo dike, which stretches for miles as a long trench (white arrow). Photo by Nathan Renfro.
Operations at Kelly Coulee, west of Yogo Creek.
Figure 3. A view up the valley known as Kelly Coulee to the west of Yogo Creek. Photo by Aaron Palke.

While Vortex is the most recently worked mine at Yogo Gulch, the bulk of the deposit lies to the east of Yogo Creek in what has become known as the Roncor property. This includes the old English mine at the far east of the deposit (figure 2), as well as the Kelly Coulee and the American mine (figure 3). In 2021, a new venture, Yogold U.S.A. Corporation, was created and acquired a lease to resume mining operations on the Roncor property. Yogold spent the summer mining open cuts of the Yogo dike as well as installing a washing plant to recover sapphires. Yogold is also actively rehabilitating the Kunisaki tunnel, which has been dormant for nearly 35 years. They plan to resume underground mining through the Kunisaki tunnel and significantly increase sapphire recovery underground.

The jewelry company Parle’ of Pocatello, Idaho, has a strategic partnership with Yogold to market loose stones and manufacture jewelry featuring Yogo sapphires. Also of interest, documentary filmmaker Orin Mazzoni is producing a short film featuring the Yogo deposit that should be of interest to anyone fascinated by these brilliant blue gems. The film is expected to be released in early 2022.

Cornflower blue Montana sapphires from Yogo.
Figure 4. A miner shows off his collection of Yogo sapphires. Photo by Aaron Palke.

There are certainly many more treasures to be unearthed at this rich deposit. While Yogo sapphires often carry a premium in the gem market for their rich cornflower blue color (figure 4) and lack of treatment, the higher overhead costs of mining in the United States pose the main challenge. But with sustained and serious mining activity in progress, the gem trade may be seeing more of the famous Yogo sapphire in the coming years.

Aaron Palke is senior manager of research, and Nathan Renfro is manager of colored stone identification, at GIA in Carlsbad, California.