 Although samples can have various color (green, brown, blue, yellow, violet, or colorless), the pure mineral is colorless as expected for a material lacking transition metals.Along with hydroxylapatite, it can be a component of tooth enamel, but for industrial use both minerals are mined in the form of phosphate rock, whose usual mineral composition is primarily fluorapatite but often with significant amounts of the other.Fluorapatite crystallizes in a hexagonal crystal system.