7.Geology and Ore Deposits of the South Silverton Mining Area, San Juan County, Colorado - by David J. Varnes - Silverton Colorado was rich in Mineral Deposits and this area covers the southern portions of this mining district. Originally published as Professional Paper 378-A, we have put this back into print for historians, prospectors and miners because it has a lot of valuable information on this district in which there are still a lot of minerals in the ground.