Fluorspar is the commercial name for the mineral fluorite, which commonly occurs as calcium fluoride (caf2). Fluorspar is the most important commercial source of fluorine, which is a pale-yellow corrosive gas. Another important source of fluorspar is phosphoric acid production, which in some cases generates the byproduct fluosilicic acid, h2sif6. The term "equivalent fluorspar" is used to refer to the amount of fluorspar that would be needed to provide an equal amount of fluorine as would be provided by the fluorine compound (i.e., the mineral itself, hydrofluoric acid, cryolite, and fluosilicic acid) being represented. This Bureau of Mines report presents comprehensive data on fluorspar including strategic considerations, problems, technology trends, reserves-resources, supply-demand relationships, economic factors and problems, operating factors and problems, and outlook to 2000.