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January-February 2013

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Fluorite in Mississippi Valley–type Deposits

However, as described below, fluorite is scarce in most MVT deposits, and only a specific group or subclass of these yields significant quantities of this mineral. Examples include the Illinois-Kentucky fluorspar district (Lillie 1988, 2006); the North Pennines orefield in the United Kingdom (Dunham 1990; Ixer and Vaughan 1993; Fisher and Greenbank 2000; Fisher 2004); Elmwood and the central Tennessee zinc district (Pasto and Stefanec 2006); the Hansonburg mining district and related deposits of the Rio Grande Rift, New Mexico (Demark and Massis 1999; Demark 2003; Rakovan and Partey 2009); and fluorite deposits of Asturias, northern Spain (Sánchez et al. 2009, 2010). The origin of fluorine (F) in these deposits is still debated and may be different in specific examples. In this article a comparison of two of the most important specimen-producing MVT districts, the Illinois-Kentucky district and the North Pennines, is presented.


Much has been written about MVT deposits since they were first recognized by Bastin (1939) as a distinct deposit type and given that name. In fact, MVTs are one of the most studied of all ore deposit types (Heyl et al. 1959; Heyl 1983; Sverjensky 1986; Sangster 1995; Paradis, Hannigan, and Dewing 2007; Leach et al. 2005; Leach et al. 2010), yet there are still outstanding questions about their origins, and they are still active areas of scientific research. One yet-unsettled question, which has direct relevance to this article, is the origin of F in those MVT deposits that host significant fluorite (CaF2) mineralization. Here we review the general geological and geochemical characteristics of MVT deposits and then focus on major fluorite producers with a comparison of two classic localities. Even though they are an ocean apart, these “sister” districts have a lot in common.

Jesse Fisher has a master's degree in geology and is a partner in UK Mining Ventures, which is operating a specimen-recovery project at the Rogerley mine in Weardale, England.

Ross Lillie, proprietor of North Star Minerals, is a former exploration geologist in the southern Illinois fluorspar district.

Dr. John Rakovan, an executive editor of Rocks & Minerals, is a professor of mineralogy and geochemistry at Miami University in Oxford, Ohio.

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