It is the site of the Dry Creek turquoise mine, which includes a rare form of turquoise which is white, with black, grey, or brown inclusions (aka matrix). The color of the matrix depends on the mineral content of the stone. This form of turquoise, known as White (sacred) Buffalo Turquoise, can be quite striking, and Garry has bought me a few pieces. Relatively rare, this stone is found only in that one mine. (However, it apparently has been often imitated in recent years, using the less precious Howlite stone). The animal namesake of White Buffalo, also quite rare, is considered to be sacred and a sign of good luck to native peoples
Garry and I have been on a quest to find pieces of white buffalo turquoise to add to my modest collection since we first discovered the stone in Cheyenne (in a shop) in 2003. It's nice to know that we have been to the mountain -- i.e., the mountain which is its source.