# Merrillite

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{{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](/source/Phosphate_mineral)
| formula     = Ca<sub>9</sub>NaMg(PO<sub>4</sub>)<sub>7</sub>
| 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](/source/Trigonal)
| class       = Ditrigonal pyramidal (3m) <br/><small>(same [H-M symbol](/source/H-M_symbol))</small>
| symmetry    = ''R3c''
| unit cell   = a = 10.362&nbsp;Å, <br/>c = 37.106&nbsp;Å; Z&nbsp;=&nbsp;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  = n<sub>ε</sub>=1.62, n<sub>ω</sub>=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](/source/phosphate_mineral) with the chemical formula Ca<sub>9</sub>NaMg(PO<sub>4</sub>)<sub>7</sub>. 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](/source/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](/source/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](/source/Ferromerrillite) 
***[Keplerite](/source/Keplerite) 	
***[Matyhite](/source/Matyhite)
***Merrillite
**Whitlockite Sub-group 		
***[Hedegaardite](/source/Hedegaardite) 
***[Strontiowhitlockite](/source/Strontiowhitlockite)
***[Whitlockite](/source/Whitlockite) 
***[Wopmayite](/source/Wopmayite)

In September 2022 the discovery of another merrillite group mineral, [changesite–(Y)](/source/changesite%E2%80%93(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](/source/George_P._Merrill) (1854–1929) of the Smithsonian Institution.<ref name="Mindat Merrillite" /> In 1915, Merrill had described the mineral from four meteorites: [Alfianello](/source/Alfianello_(meteorite)), [Dhurmsala](/source/Dhurmsala_(meteorite)), [Pultusk](/source/Pultusk_(meteorite)) and [Rich Mountain](/source/Rich_Mountain_(meteorite)). 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](/source/doi%3A10.1016%2Fj.chemer.2019.07.007)</ref> However, it was not until 1975 that it was recognized as distinct from whitlockite by the [International Mineralogical Association](/source/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](/source/lunar_rocks) and in meteorites (for example, [pallasite](/source/pallasite)s and [martian meteorite](/source/martian_meteorite)s).<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](/source/Inclusion_(mineral)) in [lower-mantle](/source/Lower_mantle_(Earth)) diamonds from [Sorriso River](/source/Sorriso_River), [Juína](/source/Ju%C3%ADna), [Brazil](/source/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}}

{{meteorites}}

Category:Phosphate minerals
Category:Meteorite minerals

{{phosphate-mineral-stub}}

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Adapted from the Wikipedia article [Merrillite](https://en.wikipedia.org/wiki/Merrillite) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Merrillite?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.