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Merrillite

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Formula:
Ca9NaMg(PO4)7
System:
Trigonal
Colour:
colorless, white
Name:
Named for George P. Merrill (May 31, 1854 - August 15, 1929), Curator of Geology, U.S. National Museum (Smithsonian Institution) by Wherry (1917)
Whitlockite Group. Mg-dominant analogue of Ferromerrillite.

Merrillite was revalidated as a valid species in 1976.
Merrill (1915) described the mineral from (at least) 4 meteorites, which may be considered type localities: Alfianello, Dhurmsala, Pultusk, Rich Mountain.

All reported non-terrestrial 'whitlockites' are actually merrillite.

Classification of Merrillite

Approved, 'Grandfathered' (first described prior to 1959)
Approval Year:
1976
8.AC.45

8 : PHOSPHATES, ARSENATES, VANADATES
A : Phosphates, etc. without additional anions, without H2O
C : With medium-sized and large cations
38.3.4.4

38 : ANHYDROUS NORMAL PHOSPHATES, ARSENATES, AND VANADATES
3 : (AB)3(XO4)2
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Occurrences of Merrillite

Geological Setting:
Stony meteorites.

Physical Properties of Merrillite

Vitreous
Colour:
colorless, white
Tenacity:
Very brittle
Cleavage:
Poor/Indistinct
Hexagonal cleavage at times (indistinct).
Density:
3.1 g/cm3 (Measured)    2.88 g/cm3 (Calculated)

Crystallography of Merrillite

Crystal System:
Trigonal
Class (H-M):
3m - Ditrigonal Pyramidal
Space Group:
R3m
Cell Parameters:
a = 10.362Å, c = 37.106Å
Ratio:
a:c = 1 : 3.581
Unit Cell Volume:
V 3450.34 ų
Z:
6

Optical Data of Merrillite

Type:
Uniaxial (-)

Chemical Properties of Merrillite

Formula:
Ca9NaMg(PO4)7
All elements listed in formula:

Relationship of Merrillite to other Species

Other Members of Group:
BobdownsiteCa9Mg(PO4)6(PO3F)
FerromerrilliteCa9NaFe2+(PO4)7
Hedegaardite(Ca,Na)9(Ca,Na)Mg(PO4)6(PO3OH)
StrontiowhitlockiteSr9Mg(PO4)6(HPO4)
TuiteCa3(PO4)2
WhitlockiteCa9Mg(PO4)6(HPO4)
8.AC.WopmayiteCa6Na3□Mn(PO4)3(PO3OH)4
8.AC.05HowardevansiteNaCuFe2(VO4)3
8.AC.10Alluaudite(Na,Ca)Mn2+(Fe3+,Mn2+,Fe2+,Mg)2(PO4)3
8.AC.10Arseniopleite(Ca,Na)NaMn2+(Mn2+,Mg,Fe2+)2(AsO4)3
8.AC.10Caryinite(Na,Pb)(Ca,Na)CaMn22+(AsO4)3
8.AC.10Ferroalluaudite(Na,Ca)Fe2+(Fe3+,Mn2+,Fe2+)2(PO4)3
8.AC.10HagendorfiteNaCaMn2+Fe22+(PO4)3
8.AC.10JohilleriteNa(Mg,Zn)3Cu(AsO4)3
8.AC.10Maghagendorfite(□,Na,)(Na,Ca,Fe2+)Mn(Mg,Fe2+,Fe3+)3(PO4)3
8.AC.10NickenichiteNa0.8Ca0.4Cu0.4(Mg,Fe)3(AsO4)3
8.AC.10VaruliteNaCaMn2+Mn22+(PO4)3
8.AC.10FerrohagendorfiteNaCaFe2+Fe22+(PO4)3
8.AC.10BradaczekiteNaCu4(AsO4)3
8.AC.10YazganiteNaFe23+(Mg,Mn2+)(AsO4)3 · H2O
8.AC.10GroatiteNaCaMn2(PO4)(HPO4)2
8.AC.15BobfergusoniteNa2Mn5FeAl(PO4)6
8.AC.15Ferrowyllieite(Na,Ca,Mn)(Fe,Mn)(Fe,Fe,Mg)Al(PO4)3
8.AC.15QingheiiteNaMn3+Mg(Al,Fe3+)(PO4)3
8.AC.15Rosemaryite(Na,Ca,Mn)(Mn,Fe2+)(Fe3+,Mg)Al(PO4)3
8.AC.15Wyllieite(Na,Ca,Mn)(Mn,Fe)(Fe,Mg)Al(PO4)3
8.AC.15Ferrorosemaryite◻NaFe2+Fe3+Al(PO4)3
8.AC.15Qingheiite-(Fe2+)Na2Fe2+MgAl(PO4)3
8.AC.18ManitobaiteNa16Mn2+ 25Al8(PO4)30
8.AC.20MarićiteNaFe2+(PO4)
8.AC.25Berzeliite(NaCa2)Mg2(AsO4)3
8.AC.25ManganberzeliiteNaCa2Mn22+(AsO4)3
8.AC.25Palenzonaite(Ca,Na)3CaMn22+(VO4)3
8.AC.25SchäferiteCa2NaMg2(VO4)3
8.AC.30BrianiteNa2CaMg(PO4)2
8.AC.35Vitusite-(Ce)Na3(Ce,La,Nd)(PO4)2
8.AC.40Olgite(Sr,Ba)(Na,Sr,REE)2Na(PO4)2
8.AC.40Bario-olgite(Ba,Sr)(Na,Sr,REE)2Na(PO4)2 ·
8.AC.45StrontiowhitlockiteSr9Mg(PO4)6(HPO4)
8.AC.45WhitlockiteCa9Mg(PO4)6(HPO4)
8.AC.45TuiteCa3(PO4)2
8.AC.45FerromerrilliteCa9NaFe2+(PO4)7
8.AC.45BobdownsiteCa9Mg(PO4)6(PO3F)
8.AC.50Chladniite{Ca}{Na8}{Ca4Na4}{(Mg,Fe2+)43}(PO4)36
8.AC.50Fillowite{Mn2+}{Na8}{Ca4Na4}{(Mn2+,Fe2+)43}(PO4)36
8.AC.50JohnsomervilleiteNa10Ca6Mg18Fe25(PO4)36
8.AC.50Galileiite{Fe2+}{Na8}{Fe42+Na4}{Fe432+}(PO4)36
8.AC.50Stornesite-(Y){(Y, Ca)}{Na62}{(Ca,Na)8}{(Mg,Fe2+)43}(PO4)36
8.AC.50XenophylliteNa4Fe72+(PO4)6
8.AC.55HarrisoniteCa(Fe2+,Mg)6(PO4)2(SiO4)2
8.AC.60KosnariteKZr2(PO4)3
8.AC.65Panethite(Na,Ca)2(Mg,Fe2+)2(PO4)2
8.AC.70StanfielditeCa4Mg5(PO4)6
8.AC.75RonneburgiteK2MnV4O12
8.AC.80Tillmannsite(Ag3Hg)(VO4,AsO4)
8.AC.85FilatoviteK(Al,Zn)2(As,Si)2O8

Other Names for Merrillite

Name in Other Languages:
German:Merrillit
Simplified Chinese:白磷钙石
Spanish:Merrillita

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Merrillite

Reference List:
Tschermak, G. (1883): Sitzber. Akad. Wiss. Wien, Math-naturw. K1.88, Abt. 1: 347-371.

Merrill, G.P. (1915): On the monticellite-like mineral in meteorites, and on oldhamite as a meteoritic constituent. Proceedings National Academy of Sciences, 1, 302-308. [as "monticellite-like mineral"]

Merrill, G.P. (1917): American Journal of Science: 43: 322.

Wherry, E.T. (1917): American Mineralogist: 2: 119. [first use of name merrillite]

Shannon and Larsen (1925): American Journal of Science: 9: 250.

Barnes (1940): University of Texas Publication 3945: 623.

Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged, 1124 pp.: 797.

Fuchs, L.H. (1962): Science: 137: 425-426.

Mason, B. (1971): Mineralogical Record: 2: 277-279.

Dowty, E. (1977): Earth and Planetary Science Letters: 35: 347-351.

Hughes,John M., Bradley L. Jolliff, and Mickey E. Gunter (2006): The atomic arrangement of merrillite from the Fra Mauro Formation, Apollo 14 lunar mission: The first structure of merrillite from the Moon. American Mineralogist, 91, 1547-1552.

Jolliff, B.L., Hughes, J.M., Freeman, J.J., Zeigler, R.A. (2006): Crystal chemistry of lunar merrillite and comparison to other meteoritic and planetary suites of whitlockite and merrillite. American Mineralogist, 91, 1583-1595.

Adcock, C. T., Hausrath, E. M., Forster, P. M., Tschauner, O., Sefein, K. J. (2014): Synthesis and characterization of the Mars-relevant phosphate minerals Fe- and Mg- whitlockite and merrillite and a possible mechanism that maintains charge balance during whitlockite to merrillite transformation. American Mineralogist 99, 1221-1232.

Internet Links for Merrillite

Localities for Merrillite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
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