Fluorspar District

INTRODUCTION

The Illinois-Kentucky District (IKFD) was, for most of the twentieth century, the primary source of fluorspar for the USA. The strategic importance of fluorspar was heightened during the Second World War (WWII) due to the use of fluorspar in steel manufacturing. Production of fluorspar ore in this region peaked shortly after WWII and production was sustained until the 1970s when competition from foreign suppliers began to erode the dominance of this mineral district. The early mines were originally operated by dozens of local entrepreneurs producing small tonnages of fluorspar, but in the 1930s corporate ventures such as Ozark-Mahoning and the Aluminum Ore Company (a precursor of ALCOA) entered the picture. The larger companies erected modern processing mills that allowed a lower grade ore to be enriched into a commercial product. Historical photographs of mines and mining activities in this district which provide a nice pictorial archive of these mines are compiled in the book “Fluorspar Mining, photos from Illinois and Kentucky, 1905-1995 (Russell H.K. 2019).

“Fluorspar” is an industrial synonym for the mineral fluorite. The chemical formula for the mineral is calcium difluoride (CaF2). The fluorspar ore found in the IKFD is usually not 100% CaF2 and contains minor impurities, mainly calcite and quartz. The ore may also contain galena, barite, and sphalerite, which can be separated and sold. For much of the 19th century, mining concentrated on galena, and fluorite was considered a waste product (Goldstein and Williams 2008). By the late 1800s, fluorspar was being utilized as a fluxing agent in the smelting of steel, which made fluorspar a valuable commodity. From 1914 to 1915, the ores of the IKFD accounted for more than 99% of fluorspar production in the United States (Weller et al. 1920). In about 1953 to 1954, the major use of fluorspar shifted from predominantly steel manufacturing to the manufacturing of hydrofluoric acid for the chemical and aluminum industries (Voskuil and Bush 1955). The primary uses of fluorspar today include the production of hydrofluoric acid and various other chemicals, steel manufacturing, aluminum smelting, hydrofluorocarbon, and fluoropolymer production (McRae 2016).