“This is a small cabinet reference specimen of a rhyolite from Shepherd Mountain, Pilot Knob, Iron County, Missouri. I personally collected this specimen on April 8, 2006 on an Earlham College petrology field trip to Missouri. This particular specimen is from an outcrop near Shepherd Mountain Lake and the specimen is identified as coming from the Stout’s Creek Rhyolite formation (Hayes, 1961). This is a fairly typical Stout’s Creek rhyolite, but contains no magnetite which is sometimes present. The Stout’s Creek rhyolite is also exposed at nearby Iron Mountain Trap Rock Co. Quarry (formerly the Iron Mountain Mine [http://www.mindat.org/loc-44224.html]), where it is quarried for landscaping rock and railroad aggregate. Shepherd Mountain was the former location of an iron mine that was active before the Civil War, but was never a major producer unlike the nearby Pilot Knob Mine or the Iron Mountain Mine, only in operation from 1815 to 1850. Experimental drilling had been carried out in 1888, 1930 and 1961 to see if the locality had any further potential, but it did not (Hayes, 1961). Jamison K. Brizendine specimen and photo. References Cited: Hayes, W., 1961, Geology of the St. Francois Mountain area: State of Missouri Department of Business and Administration, Department of Geological Survey and Water Resources, Report of Investigations, v. 26”