Editing Apatite (section)

== Apatite group and supergroup ==
Apatite is the prototype of a class of chemically, stoichometrically or structurally similar minerals, biological materials, and synthetic chemicals.<ref>[https://www.tomshardware.com/news/lk-99-patent-update-suggest-it-could-work J.C. Elliott, Structure and Chemistry of the Apatites and Other Calcium Orthophosphates (1994)]</ref> Those most similar to apatite are also known as apatites, such as [[lead apatite]] ([[pyromorphite]]) and barium apatite ([[alforsite]]). More chemically dissimilar minerals of the apatite supergroup include [[belovite group|belovite]]s,  [[britholite]]s, [[ellestadite]]s and [[lead apatite|hedyphane]]s.

Apatites have been investigated for their potential use as pigments (copper-doped alkaline earth apatites), as [[phosphor]]s and for absorbing and immobilising toxic heavy metals.

In apatite minerals [[strontium]], [[barium]] and [[lead]] can be substituted for calcium; [[arsenate]] and [[vanadate]] for phosphate; and the final balancing anion can be [[fluoride]] (fluorapatites), [[chloride]] (chlorapatites), [[hydroxide]] (hydroxyapatites) or [[oxide]] (oxyapatites). Synthetic apatites add [[hypomanganate]], [[hypochromate]], [[bromide]] (bromoapatites), [[iodide]] (iodoapatites), [[sulfide]] (sulfoapatites), and [[selenide]] (selenoapatites). Evidence for natural sulfide substitution has been found in lunar rock samples.<ref>{{cite journal|last1=Brounce|first1=Maryjo|last2=Boyce|first2=Jeremy W.|last3=Barnes|first3=Jessica|last4=McCubbin|first4=Francis McCubbin|title=Sulfur in the Apollo Lunar Basalts and Implications for Future Sample-Return Missions|journal=Elements|volume=16|issue=5|date=June 2020|page=361-2|doi=10.2138/gselements.16.5.361 |bibcode=2020Eleme..16..361. }}</ref>

Furthermore, compensating substitution of monovalent and trivalent cations for calcium, of dibasic and tetrabasic anions for phosphate,  and of the balancing anion, can occur to a greater or lesser degree. For example, in biological apatites there is appreciable substitution of sodium for calcium and carbonate for phosphate, in belovite sodium and [[cerium]] or [[lanthanum]] substitute for a pair of divalent metal ions, in germanate-pyromorphite [[germanate]] replaces phosphate and chloride, and in ellestadites silicate and sulphate replace pairs of phosphate anions. Metals forming smaller divalent ions, such as magnesium and iron, cannot substitute extensively for the relatively large calcium ions but may be present in small quantities.<ref>{{cite journal|last1=Kogarko|first1=Lia|title=Chemical Composition and Petrogenetic Implications of Apatite in the Khibiny Apatite-Nepheline Deposits (Kola Peninsula)|journal=Minerals|volume=8|issue=11|date=16 November 2018|page=532|doi=10.3390/min8110532|doi-access=free|bibcode=2018Mine....8..532K }}</ref>