Plains, wells drilled deep into this unit provide an inexhaustible supply of cold artesian, Rocky Mountain...instance, a single Spodumene crystal from the Etta Mine near Keystone on the east side of the Mount Rushmore...beds, excavations, etc.Selenite roses. BRULE COUNTY AREA: in the Oacoma zone of the Pierre Fm. On Elm...gray Barite rosette up to 5 or 6 inches. CAMPBELL COUNTY MOUND CITY, W to the Missouri R., regional hillsides...tributary gravels, etc.petrified wood, wood opal. CORSON COUNTY LITTLE EAGLE: area ridges, slopes, stream |