Transformation of Calcite CaCO3 to Fluorite CaF2 by Action of KF Solution

Conversion of microcrystalline calcium carbonate powder to fluorite by reacting it with potassium fluoride solution is studied. The reaction occurs at room temperature and yields a white flowing powder. Rhombohedral CaCO 3 microcrystals are replaced by an ensemble of CaF 2 nanoparticles sized ca. 20 nm, which in part fill in the volume of the precursor microcrystals. The product calcium fluoride contains about 2 mol % KF. KCaF 3 is not produced by the reaction, and KCaF 3 is a high-temperature compound stable above 500 о С.