Merrillite

{{Short description|Phosphate mineral}} {{Infobox mineral | name = Merrillite | boxwidth = | boxbgcolor = | image = Meteorite Renchen, Sample R3A, Merrillite-Apatite Aggregate and Troilite.jpg | imagesize = | alt = | caption = | category = Phosphate mineral | formula = Ca9NaMg(PO4)7 | IMAsymbol = Mer<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3 |pages=291–320|doi=10.1180/mgm.2021.43 |bibcode=2021MinM...85..291W |s2cid=235729616 |doi-access=free}}</ref> | molweight = | strunz = 8.AC.45 | dana = | system = Trigonal | class = Ditrigonal pyramidal (3m) (same H-M symbol) | symmetry = ''R3c'' | unit cell = a = 10.362 Å, c = 37.106 Å; Z = 6 | color = Colorless to white | colour = | habit = Occurs as anhedral grains | twinning = | cleavage = Poor - indistinct | fracture = | tenacity = Brittle | mohs = | luster = Vitreous | streak = | diaphaneity = | gravity = 3.1 (measured) | density = | polish = | opticalprop = Uniaxial (-) | refractive = nε=1.62, nω=1.623 | birefringence = 0.0030 | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | prop1 = | prop1text = | references = <ref>[https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Merrillite Mineralienatlas]</ref><ref name=Webmin>[http://www.webmineral.com/data/Merrillite.shtml Merrillite data on Webmineral]</ref><ref name="Mindat Merrillite"/> }} '''Merrillite''' is a calcium phosphate mineral with the chemical formula Ca9NaMg(PO4)7. It is an anhydrous, sodium-rich member of the merrillite ''group'' of minerals.<ref name="Mindat Merrillite">{{cite web|title=Merrillite|url=http://www.mindat.org/min-6577.html|publisher=Mindat|accessdate=6 January 2013}}</ref><ref name="Mindat Merrillite Group">{{cite web|title=Merrillite|url=https://www.mindat.org/min-55746.html|publisher=Mindat|accessdate=13 September 2022}}</ref>

==Mineral species, sub-group and group== Merrillite is a distinct ''mineral species'' but it also gives its name to a set of similar minerals, which together form the merrillite ''sub-group'' of minerals. The merrillite sub-group and the whitlockite sub-group together form the merrillite ''group'' of minerals.<ref name="Mindat Cerite Supergroup">{{cite web|title=Cerite Supergroup|url=https://www.mindat.org/min-55118.html|publisher=Mindat|accessdate=13 September 2022}}</ref>

*Merrillite Group<ref name="Mindat Cerite Supergroup"/> **Merrillite Sub-group ***Ferromerrillite ***Keplerite ***Matyhite ***Merrillite **Whitlockite Sub-group ***Hedegaardite ***Strontiowhitlockite ***Whitlockite ***Wopmayite

In September 2022 the discovery of another merrillite group mineral, changesite–(Y), was announced,<ref name="ChinaDaily">{{cite web|title=New mineral found by Chinese scientists|url=https://www.chinadaily.com.cn/a/202209/10/WS631bd991a310fd2b29e76f79.html|publisher=China Daily|accessdate=13 September 2022}}</ref> but, {{As of|2022|09|lc=y}}, it is not yet clear where this new mineral sits in the merrillite group hierarchy.

==Discovery and naming== Merrillite is named after George P. Merrill (1854–1929) of the Smithsonian Institution.<ref name="Mindat Merrillite" /> In 1915, Merrill had described the mineral from four meteorites: Alfianello, Dhurmsala, Pultusk and Rich Mountain. Merrillite has also been reported from the [https://de.wikipedia.org/w/index.php?title=Renchen_(Meteorit)&stable=1 Renchen meteorite] (a well-documented fall that occurred on 10 July 2018 at 21:29 UTC in southwestern Germany), occurring in the form of a merrillite–apatite aggregate.<ref>Bischoff, A.; Barrat, J.-A.; Berndt, J.; Borovicka, J.; Burkhardt, C.; Busemann, H.; Hakenmüller, J.; Heinlein, D.; Hertzog, J.; Kaiser, J.; Maden, C.; Meiere, M. M. M.; Morino, P.; Pack, A.; Patzek, M.; Reitze, M. P.; Rüfenacht, M.; Schmitt-Kopplin, P.; Schönbächler, M.; Spurný, P.; Weber, I.; Wimmer, K.; Zikmund, T. (2019): [https://www.sciencedirect.com/science/article/pii/S0009281919300133 The Renchen L5-6 chondrite breccia – The first confirmed meteorite fall from Baden-Württemberg (Germany)], Geochemistry, Volume 79, Issue 4, P. 125525 (19 Pages), doi:10.1016/j.chemer.2019.07.007</ref> However, it was not until 1975 that it was recognized as distinct from whitlockite by the International Mineralogical Association.<ref name="Mindat Merrillite" />

==Occurrence== Merrillite is a very important constituent of extraterrestrial rocks.{{citation needed|date=September 2022}} It occurs in lunar rocks and in meteorites (for example, pallasites and martian meteorites).<ref name="Jolliff 2006">{{cite journal|last=Jolliff|first=Bradley L.|author2=John M. Hughes |author3=John J. Freeman |author4=Ryan A. Zeigler |name-list-style=amp |title=Crystal chemistry of lunar merrillite and comparison to other meteoritic and planetary suites of whitlockite and merrillite|journal=American Mineralogist|date=2006|volume=91|issue=10|pages=1583–1595|doi=10.2138/am.2006.2185|bibcode=2006AmMin..91.1583J|s2cid=140580667}}</ref>

In 2022, for the first time, merrillite was found in a terrestrial environment, as an inclusion in lower-mantle diamonds from Sorriso River, Juína, Brazil.<ref>{{cite journal |last1=Kaminsky |first1=Felix V. |last2=Zedgenizov |first2=Dmitry A. |title=First find of merrillite, Ca3(PO4)2, in a terrestrial environment as an inclusion in lower-mantle diamond |journal=American Mineralogist |date=2022 |volume=107 |issue=8 |pages=1652–1655 |doi=10.2138/am-2022-8175|s2cid=251071674 }}</ref>

==References== {{Reflist}}

Category:Phosphate minerals Category:Meteorite minerals