Fluorspar in Brewster County, Texas

Bureau Publication GC6702 - to purchase a print copy please go to: https://store.beg.utexas.edu/geologic-circulars/389-gc6702.htmlSince production of fluorspar began in northern Coahuila, Mexico, in 1950-51, thousands of tons of high-grade ore have been mined from numerous deposits situated 5 to 75 miles south of the Rio Grande. A large part of the fluorspar mined from these deposits has moved northward through Boquillas, Stillwell Crossing, and Heath Crossing to the railhead at Marathon, Texas. Consequently, Marathon has become one of the principal fluorspar shipping points in the world. Even though none of the nearly two million tons of fluorspar shipped from Marathon during the last 15 years came from a deposit in Texas, several occurrences of fluorite are known in southern Brewster County, Texas: the northern Mexico fluorspar province does not terminate abruptly at the Rio Grande. Deposits in Mariscal Mountain in Big Bend National Park are possibly equal in size and grade to deposits 5 to 10 miles southward across the Rio Grande in the San Vicente district. Potentially commercial deposits are known at several places in and around the Christmas Mountains (just outside the northwestern boundary of Big Bend National Park), and fluorite mineralization is widespread throughout the Terlingua quicksilver district. Cretaceous limestone formations which serve as host rocks for fluorspar deposits in northern Coahuila crop out extensively in Brewster County, Texas in the following areas: the Dove Mountain--Maravillas and Reagan Canyon country, on the flanks of the Marathon Dome, in the Sierra del Carmen--Santiago--Del Norte Range, in the Christmas Mountains--Corazones Peaks area, in the Terlingua quicksilver district, and in Mariscal Mountain in Big Bend National Park. But, in Brewster County, as in Coahuila, fluorspar deposits are found only in close proximity to rhyolite intrusions. The intrusive rocks in southeastern Brewster County are dominantly syenodioritic in composition and most of the intrusions north of the Christmas Mountains--Corazones Peaks area are trachytes and microsyenites.Bureau of Economic GeologyUT Librarie