Calcium Fluoride — Frequently Asked Questions

Because it is the only commercially significant source of fluorine and has no substitute at scale. Every fluoropolymer, refrigerant, fluorinated pharmaceutical and agrochemical, and aluminium smelting flux traces back to hydrogen fluoride made from acid grade fluorspar. Combined with geographically concentrated supply, that dependency puts it on the critical raw materials lists of the EU, the US and China.

Because silica consumes hydrogen fluoride. In the reaction with sulphuric acid, any silica present reacts with the HF being produced to form silicon tetrafluoride, directly reducing yield and creating a gas that must be scrubbed. Acid grade is therefore specified on silica content as tightly as on CaF2 assay.

It fluidises the slag. Adding fluorspar lowers the melting point and viscosity of the slag layer, which allows sulphur and phosphorus to partition into it far more efficiently and makes the slag easier to remove. Metallurgical grade is used as received, since the impurities that matter for chemical conversion are largely irrelevant here.

Because it transmits across a far wider spectral range than glass, from deep ultraviolet through to infrared, and has very low dispersion. Single crystals grown for this purpose are used in ultraviolet lithography optics, in infrared spectroscopy windows and in high-performance camera lenses where chromatic aberration must be minimised.