H2SiF6-2H(2)O was sepd. from H3PO4 prodn. mixt. and treated with chalk to obtain CaF2 by pptn. F ions at 20 degrees C in presence of 2 corn. flocculants. The product of the high purity (94% by mass CaF2) and low SiO2 content (1.79% by mass) was obtained at Ca-to-F molar ratio 0.5 and lig. phase mass to a suspended solid chalk ratio equal to 50:1.