The chief foreign producer of fluorspar is Great Britain, and much of this product comes to the United States. Canada produces a small amount, some of which also comes to the United States. Several thousand tons are produced yearly in Germany and France, and are largely consumed there.
The production of fluorspar in the United States is several times that of any other country. The ore mined comes principally from the southern Illinois and western Kentucky field, and is used largely for fluxing purposes in open-hearth steel furnaces. Minor amounts are produced in Colorado, New Mexico, and other states.
The United States has sufficient supplies of fluorspar to meet all its own demands for this material. Small amounts, however, are imported for use in eastern furnaces because the material can be brought over from England very cheaply. The domestic fluorspar is suitable for practically all purposes for which fluorspar is used except for lenses in optical instruments. For this use very small quantities of material imported from Japan have been used, but recently fluorspar of a grade suitable for optical purposes has been found in Illinois, Kentucky, New Hampshire, and other states. For fluxing purposes domestic fluorspar is superior to the foreign product.
Fluorspar is the trade name for the mineral fluorite, which is composed of calcium fluoride. This is a common mineral in veins and replacements which carry ores of zinc, lead, silver, gold, copper, and tin. It is formed under a variety of conditions, but is always ascribed to solutions coming from nearby igneous rocks.
The large fluorspar deposits of Illinois and Kentucky contain fluorite with calcite, barite, and metallic sulphides, in wide veins filling fissures in limestones and sandstones and replacing the fissure walls. Into these sediments there are intruded certain peridotite dikes. The fluorite and associated minerals were probably deposited by hot solutions bringing the material from some large underlying igneous mass of which the dikes are off-shoots.
In the western United States many metalliferous deposits carry large amounts of fluorite, which is treated as a gangue or waste mineral, but which could be profitably extracted if there were local markets. In England, fluorite is obtained in this manner as a by-product from lead and zinc mines.