3 U.S. Bureau of Mines, Randol Mining Directory 1994/1995, Randol International Ltd., Golden, CO, 1994, p. 165. 4 M.M. Miller, 1994, Op. Cit., p. 58. ... Before fluorspar can be used to make hydrofluoric acid, the raw ore must be physically concentrated and purified. Ceramic and acid gr ades of fluorspar are concent rated (not shown) by ...Web