The US Platinum Group Metals (PGM) operations comprise the Stillwater, Stillwater East (formerly the Blitz Expansion Project) and East Boulder Mines and the Columbus Metallurgical Complex, respectively.
Stillwater and East Boulder are shallow to intermediate level underground Platinum Group Metals (PGM) mines situated 85 miles southwest of Billings in Sweet Grass County approximately 32 miles south of the town of Big Timber, in the state of Montana, in the US.
In 1883, prospectors recognised that the Stillwater Complex contained copper, nickel and chromium deposits. The first identified deposits outcropped on the surface and were geologically mapped and explored as sources for copper, nickel and chromium. The chromium was determined to represent a strategic resource and, starting in the late 1930s, was actively mined to secure a domestic source of chromium which was processed on the current Stillwater operation facilities site.
In 1983, Chevron, Manville and Anaconda formed the Stillwater Mining Company (SMC) to pursue exploration and test mining in the Stillwater valley. In 1986, SMC completed construction of a concentrator and tailings impoundment and went into production. In 1994, the company went public and in 2002 it brought the East Boulder operation into commercial production.
The East Boulder Mine is characterised by 16 heritage sites in total, consisting mostly of lithic material scatter and Stillwater mine has a total of 52 heritage sites to date, consisting mostly of historic mining sites, historic homesteads and roads/trails.
