Editing Mineral (section)

====Phosphates====
{{main article|Phosphate minerals}}
The [[phosphate minerals]] are characterized by the tetrahedral [PO<sub>4</sub>]<sup>3−</sup> unit, although the structure can be generalized, and phosphorus is replaced by antimony, arsenic, or vanadium. The most common phosphate is the [[apatite]] group; common species within this group are fluorapatite (Ca<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>F), chlorapatite (Ca<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>Cl) and hydroxylapatite (Ca<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>(OH)). Minerals in this group are the main crystalline constituents of teeth and bones in vertebrates. The relatively abundant [[monazite]] group has a general structure of ATO<sub>4</sub>, where T is phosphorus or arsenic, and A is often a [[rare-earth element]] (REE). Monazite is important in two ways: first, as a REE "sink", it can sufficiently concentrate these elements to become an ore; secondly, monazite group elements can incorporate relatively large amounts of uranium and thorium, which can be used in [[monazite geochronology]] to date the rock based on the decay of the U and Th to lead.<ref>{{harvnb|Dyar|Gunter|2008}}, pp. 675–80</ref>