The Sterling Bros Mine is a copper mine.
Background
The Sterling Bros Mine is where Les was led to by Jebidiah and Homer Smith in the hope he would believe it was the Menkey Butte Mine. Some of the locals refer to it as "Blood Rock" to travelers.
Appearances
The Sterling Bros Mine is mentioned in the short story Menkey Butte Mine published in The Armageddon Rag, Vol. 4.