Calcium borate

Calcium borate (Ca₃(BO₃)₂), also called Gerstley borate, is a bluish white crystal with a very defined structure. It can be prepared by reacting calcium metal with boric acid. The resulting precipitate is calcium borate. A hydrated form occurs naturally as the minerals colemanite, nobleite and priceite.

One of its uses is as a binder in some grades of hexagonal boron nitride for hot pressing. Other uses are e.g. flame retardant in epoxy molding compounds, a ceramic flux in some ceramic glazes, reactive self-sealing binders in hazardous waste management, additive for insect-resistant polystyrene, fertilizer, and production of boron glasses.