Map showing areas with potential for garnet resources in bedrock and placer in the Blacktail Mountains and the Gravelly, Greenhorn, Ruby, and Snowcrest ranges of southwestern Montana

Garnet crystals, some of gem quality, have been sought by rock hounds for many years in the alluvial deposits of the Alder Gulch-Ruby River area. Since 1995, garnet have been extracted from these gravels for industrial products at two separately own placer mines in the region: (1) at Cominco American's "Ruby Garnet" operation at Alder , Montana and (2) at the "Sweetwater Garnet" operation in the Sweetwater Basin of the Ruby Range. The two placer mines excavate different types of garnetiferous deposits, but both produce sized concentrates of almandine garnet derived from similar source rocks.