Bentonite Mine to Resume Operation After Hiatus

Mining is not a major industry in Valley County, but it has seen historical significance. Beside coal of the old days and gravel pits scattered throughout the county, bentonite is the only mineral that has brought commercial value to the county. Developed in the 1960s, the bentonite mine outside Glasgow is proposing to start extraction again.

The bentonite mine is owned by S&B Industrial Minerals based in Berwyn, Pennsylvania. It is located about 20 miles southwest of Glasgow on Bentonite Road. It was active five years ago when S&B mined, then reclaimed, five acres under the permit “Bent Hill” issued by the Montana Department of Environmental Quality (DEQ). Earlier this year, S&B submitted another plan of operation to DEQ, proposing to disturb an additional 12.8 acres adjacent to the previously mined 5-acre area. The Bureau of Land Management (BLM) is in the process of preparing an Environmental Assessment for this project as the mine is located on BLM land.

Under the proposed plan “Bent #4,” the mine would use open cut mining technique to strip the bentonite deposit. The material would then be hauled to a laydown area two miles north, spread out on the ground to field-dry, then transported to the city of Glasgow.

According to Craig Towery, geologist in BLM’s Lewistown Field Office, the bentonite deposit can often been seen as layers of fine ash-like clay outcropping near ground surface. At the proposed mining location, there are two layers of bentonite deposit—each two to three feet thick—so that the overall mine pit depth is probably not more than 30 feet, according to Towery. Too deep an overburden would render the mining uneconomical. The work period is from July 15 to December 1, although the starting date has not been specified, explained Towery.

The proposed ban on certain types of mining in the Sagebrush Focal Areas on local BLM lands –announced last week by the Department of Interior to protect greater sage grouse—will not affect the bentonite mine because S&B holds valid existing claims, according to Pat Gunderson, supervisor of the BLM field office in Glasgow. S&B holds a land lease package that contains 800-900 acres, all of which are within the Sagebrush Focal Area, said Gunderson.

Besides greater sage grouse, mountain plover is another bird species that relies on the habitat offered by sparsely-vegetated prairie common in south Valley County. BLM’s designated Mountain Plover Area of Critical Environmental Concern is adjacent to the mine. The mine’s reclamation plan requires that disturbance be reclaimed to pre-mine land use, which is wildlife habitat and grazing, according to Gunderson. He points out that reclamation of the disturbance from five years ago has been successful—unsuspecting eyes might not be able to detect that the ground had been mined.

Towery indicated that one comment was received during the public scoping period for the proposed project. It was in favor.

Bentonite contains the clay mineral, montmorillonite, which swells when it absorbs water. It is responsible for forming the “gumbo” mud that northeast Montanans are so familiar with. However, it is also an ingredient in many everyday products such as cosmetics, paint, and masonry, and is a clarifying agent in wine. Bentonite is also used for oil well drilling mud and sealant.

An online archive of the 1977 Environmental Impact Statement on the mine told a piece of history of the mine as a major operation. Federal Bentonite Company acquired the lease from Brazil Creek Bentonite Company in 1965, developed the mine extensively in the late 1960s, and built a railroad spur from Glasgow to the mine in 1969-1970. In 1977, Federal proposed to mine an additional 180 acres and build a drying plant in phases. It had anticipated to mine 2000 acres in the next five years, with a projected mine life of 20 years. In 1976, Federal paid $25.26 on the quarter-section property where the proposed plant would be located. Local contractors were hired back then; that certainly would add economic benefit to the County today.