Apatite is a group of phosphate minerals which includes: fluorapatite, chlorapatite, hydroxylapatite, carbonate-rich apatite and francolite. The term "apatite" is often used for fluorapatite, the most common of these minerals. Apatite is found in igneous, metamorphic and sedimentary rocks. The most extensive deposits are the sedimentary "phosphate rocks", which are mined to produce phosphate fertilizer.