Manganese deposits of Cedar Creek Valley, Frederick and Shenandoah Counties, Virginia

Abstract

The Cedar Creek manganese mining district is in the southwestern part of Frederick County and the northwestern part of Shenandoah County, Virginia. The manganese ore consists chiefly of the oxides' pyrolusite and psilomelane, and forms replacement pockets and fracture fillings in the Oriskany sandstone and in residual sandy clay and chert derived from the New Scotland limestone. Both these formations are of Devonian age, and both form low ridges. The minable bodies have been deposited by ground water in the zone of weathering, and most of them lie above present ground-water level. The manganese-bearing formations, together with the older and younger formations exposed in Cedar Creek Valley, have been compressed into numerous folds, and at the southwestern end of the district one of these folds passes into a normal fault with a displacement of 1,000 feet or more. Manganese ore has been mined in the valley since 1834, and about 15,000 tons of ore had been shipped from four mines before 1941. Most of the marketed manganese ore from Cedar Creek Valley has been sold to the chemical and brick industries and only a minor part has been sold as metallurgical ore. Because ore for chemical and brick purposes has commanded a higher price than that generally paid for metallurgical ore, mining in the valley has to some extent been carried on during times of low prices for metallurgical ore. The ratio of recoverable manganese concentrates to manganese-bearing rock varies considerably, the maximum being about 1 ton of concentrates to 6 tons of crude ore and the minimum about 1 ton of concentrates to about 15 tons of crude ore. It is estimated that about 30,000 tons of manganese concentrates containing 40 percent or more of manganese will be recoverable in the proved mining areas in Cedar Creek Valley during times of high prices for manganese; and this tonnage of recoverable concentrates may be doubled by further exploration of the present known ore bodies.