Feldspar is one of the most abundant minerals in the earth's crust. The feldspars include a range of compositions with a general chemical formula of xAl(Al,Si)3O8 where x can be sodium (Na) and/or calcium (Ca) and/or potassium (K). They are primarily used in glass and ceramics making. In glass, they improve hardness and durability. In ceramics, feldspar is used as a flux to lower melting temperatures during the firing process.Year of first production in Virginia: 1880s
Location of first production in Virginia: Amelia County
Year of last production in Virginia: actively producing
Location of current production: Hanover County, Amherst County
Currently, Virginia has two mines actively producing feldspar, both from anorthosite intrusions. Anorthosite is an igneous rock consisting of predominantly plagioclase feldspar with minor amounts of pyroxene, olivine, and iron oxides. The Montpelier anorthosite in Hanover County is mined by U. S. Silica Corporation for feldspar to be used in the manufacturing of container glass and insulation fiber glass. The feldspar provides alumina, which improves durability of the glass. The feldspar-rich rock is extracted using open pit methods, then crushed, classified and dried on-site. Heavy minerals are removed from the material by electrostatic and magnetic processes. The processed material is then transported by truck and rail to markets. Feldspar is also mined from the Roseland anorthosite body at the Piney River Quarry in Amherst County by Boxley Materials Company for use as aggregate (production tonnage for this quarry not included in graph below).
Historically, feldspar in Virginia was mined for use in the ceramics industry, for abrasives, and for gemstones (amazonite) (Pegau, 1932). Prior to 1907, according to Watson (1907) feldspar was mined primarily in connection with mica mining. It was mined by open pit method predominantly from pegmatite deposits in Bedford, Prince Edward, and Amelia Counties in the early part of the twentieth century.
Feldspar production and value, 1986-2003.
Bice, K. L., and Clement, S. C., 1982, A study of the feldspars of the Montpelier andesine anorthosite, Hanover County, Virginia: Geological Society of America Abstracts with Programs,v. 14, p. 5.
Brown, W. R., 1962, Mica and feldspar deposits of Virginia: Virginia Division of Mineral Resources Mineral Resource Report 3, 195 p.
Clement, S. C., and Bice, K. L., 1982, Andesine anorthosite in the Eastern Piedmont of Virginia: Geological Society of America Abstracts with Programs, v. 14, p. 10.
Owens, B. E. & Dymek, R. F., 1999, A geochemical reconnaissance of the Roseland anorthosite complex, Virginia, and comparisons with andesine anorthosites from the Grenville Province, Quebec: in: A. K. Sinha (editor), Basement Tectonics, v. 13, p. 217-232.
Pegau, A. A., 1932, Pegmatite deposits of Virginia: Virginia Division of Mineral Resources Bulletin, v. 33, p. 3-122.
Potter, Michael J., 2003, Feldspar: U.S. Geological Survey Mineral Commodity Summaries, p. 62-63.
Virginia Division of Mineral Resources, 1993, Geologic Map of Virginia: Virginia Division of Mineral Resources, scale 1:500,000.
Watson, T. L., 1907, Mineral Resources of Virginia: Lynchburg, Virginia, Jamestown Exposition Commission, 618 p.
(available as Virginia Division of Mineral Resources, 2003, Digital reprint of T. L. Watson’s 1907 Mineral resources of Virginia: Virginia Division of Mineral Resources Publication 175, [CD-ROM; 2003, September 1].