Fluorite

Fluorite is the mineral form of calcium fluoride. It has a chemical formula of CaF2 where Ca stands for calcium, and F2 stands for Fluorine. 
Fluorite is the main source of fluorine and fluorides. It naturally fluoridates drinking water in places where it is found. It has a hardness of 5. It barely dissolves in water. Geologists have found about 9000 deposits of fluorite found on the Earth. It is mainly mined in China, Mexico and Russia.