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Gunpowder was a critical material during the Civil War and much of the Confederate gunpowder supplies were derived from niter (saltpeter) deposits that form in western Virginia caverns. Robert Whisonant from Radford University provides a thorough overview of the geology and history of saltpeter production during the Civil War in the November 2001 issue of Virginia Minerals.
The main ingredient in black gunpowder is potassium nitrate, a compound derived from niter or saltpeter. Saltpeter is a potassium nitrate (KNO3) that commonly forms in cave deposits; other nitrate minerals (nitro-magnesite and nitrocalcite) also occur in Virginia cave deposits. These nitrates form through a complex process that starts when nitrogen fixed by bacteria is transported in the shallow groundwater system and reprecipitated as the groundwater evaporates in the pore space of cave sediments.
 Entrance to a niter-producing cave in western Virginia. (Courtesy of Karen M. Kastning and Ernst H. Kasting, Jr.) |
Caverns are common in the Valley and Ridge province of western Virginia. Here, folded layers of limestone and dolomite are dissolved by naturally acidic groundwater in the subsurface to form caves. Flowing water tends to deposit sand and clay on the floor of many caves and it is in this sediment that saltpeter may accumulate.
Virginia was the leading niter producer during the Civil War with an estimated total production of about 500,000 pounds. Saltpeter was mined on a small-scale at over 100 caves in western Virginia. Whisonant notes that because saltpeter production was widely scattered at many caves, it never was the principal target of Union attacks on strategic commodities and many saltpeter caves were still being mined at the end of the war.
Whisonant, R. C., 2001, Geology and history of confederate saltpeter cave operations in western Virginia. Virginia Minerals, v. 47, n. 4, p. 33- 43.
