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|Name:||Named for George P. Merrill (1854-1929), 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
|IMA status:||Approved 1976|
|Explanation of status:||revalidated in 1976 (IMA 76-K) as not identical to whitlockite|
|Strunz 8th edition ID:||7/A.05-55|
|Nickel-Strunz 10th (pending) edition ID:||8.AC.45|
8 : PHOSPHATES, ARSENATES, VANADATES
A : Phosphates, etc. without additional anions, without H2O
C : With medium-sized and large cations
|Dana 8th edition ID:||126.96.36.199|
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
Hexagonal cleavage at times (indistinct).
|Density (measured):||3.1 g/cm3|
|Density (calculated):||2.88 g/cm3|
Crystallography of Merrillite
|Class (H-M):||3m - Ditrigonal Pyramidal|
|Cell Parameters:||a = 10.362Å, c = 37.106Å|
|Ratio:||a:c = 1 : 3.581|
|Unit Cell Volume:||V 3450.34 Å³|
Optical Data of Merrillite
Chemical Properties of Merrillite
|Simplified for copy/paste:||Ca9NaMg(PO4)7|
|Essential elements:||Ca, Mg, Na, O, P|
|All elements listed in formula:||Ca, Mg, Na, O, P|
Relationship of Merrillite to other Species
|Member of:||Whitlockite Group|
|Other Members of Group:|
|Related Minerals - Nickel-Strunz Grouping):|
Other Names for Merrillite
|Health Warning:||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
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
The 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.
(TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
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