Fluoride

Fluorite (also called fluorspar) is a mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon. Cubic crystals up to 20cm across have been found at Dalnegorsk, Russia.[1] Crystal twinning is common and adds complexity to the observed crystal habits.

Magnesium fluoride (MgF2) is a white crystalline salt composed of one magnesium ion and two fluoride ions, and is used in the electrolysis of aluminum ore. It is a tetragonal, birefringent crystal.

Potassium fluoride is the chemical compound with the formula KF. After hydrogen fluoride, KF is the primary source of the fluoride ion for applications in manufacturing and in chemistry. It is an alkali metal halide and occurs naturally as the rare mineral carobbiite. Aqueous solutions of KF will etch glass due to the formation of soluble fluorosilicates, although HF is more effective.