Long bladed Stibnite crystals in compacted texture. The exact locality on Lolo Pass is not known.
Stibnite is the chief of antimony. It's use is varied and about 50% of the antimony produced is used for metal alloys in storage batteries, power transmission equipment, solder, bearings, and ammunition. It is not ductile nor malleable and has a low melting poit of 630.5 deg. C.