Merrillite Mineral Data

General Merrillite Information

Chemical Formula:

Ca18Na2Mg2(PO4)14

Composition:

Molecular Weight = 2,145.59 gm

Sodium 2.14 % Na 2.89 % Na₂O

Calcium 33.62 % Ca 47.04 % CaO

Magnesium 2.27 % Mg 3.76 % MgO

Phosphorus 20.21 % P 46.31 % P₂O₅

Oxygen 41.76 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Ca₁₈Na₂Mg₂(PO₄)₁₄

Environment:

Extraterrestrial bodies. The name merrillite was proposed in 1917.

IMA Status:

Approved IMA 1977

Locality:

Meteorites Link to MinDat.org Location Data.

Name Origin:

Named after George Perkins Merrill (1854-1929), meteorite specialist at U. S. National Museum, Smithsonian Institution, Washington, D.C. USA.

Synonym:

Merrillite-Na

Merrillite Image

Images:

Merrillite

Comments: BSE image of merrillite intergrown with silicates (plagioclase (plag), orthopyroxene(opx), olivine(ol)) next to coarse FeNi-metal (white).
Location: Portales Valley meteorite (1988). Scale: See Image.
© Alex Ruzicka / Planetary Science Research

Merrillite Crystallography

Axial Ratios:

a:c = 1:3.58096

Cell Dimensions:

a = 10.362, c = 37.106, Z = 3; V = 3,450.34 Den(Calc)= 3.10

Crystal System:

Trigonal - Ditrigonal PyramidalH-M Symbol (3m) Space Group: R 3c

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 2.85(1), 2.58(0.6), 3.19(0.6),3.43(0.6), 5.18(0.6), 1.71(0.5), 1.92(0.5), 1.54(0.4),

Crystal Structure:

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Hughes J M , Jolliff B L , Rakovan J , American Mineralogist , 93 (2008) p.1300-1305, The crystal chemistry of whitlockite and merrillite and the, dehydrogenation of whitlockite to merrillite, Locality: synthetic, Note: Formed through dehydrogenation of synthetic whitlockite, by heating at 1050 degrees C for 24 hours

Physical Properties of Merrillite

Habit:

Anhedral Grains - Granular minerals without the expression of crystal shapes

Optical Properties of Merrillite

Gladstone-Dale:

CI calc= -0.02 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2005,KC= 0.1965
Ncalc = 1.61

Optical Data:

Uniaxial (-), e=1.62, w=1.623, bire=0.0030.

Calculated Properties of Merrillite

Electron Density:

Bulk Density (Electron Density)=3.07 gm/cc
note: Specific Gravity of Merrillite =3.10 gm/cc.

Fermion Index:

Fermion Index = 0.0029199202
Boson Index = 0.9970800798

Photoelectric:

PE_Merrillite= 5.19 barns/electron
U=PE_Merrillite x rElectron Density= 15.95 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Merrillite is Not Radioactive

Merrillite Classification

Dana Class:

38.03.04.04 (38)Anhydrous Phosphates, etc

(38.03)(A+ B++)3 (XO4)2

(38.03.04)Whitlockite group

38.03.04.01 Whitlockite Ca9(Mg,Fe)(PO4)6(PO3OH) R 3c 3m

38.03.04.02 Strontiowhitlockite Sr7(Mg,Ca)3(PO4)6[PO3(OH)] R 3c 3m

38.03.04.03 Merrillite-(Ca)* (Ca,[])19Mg2(PO4)14 R 3c 3m

38.03.04.04 Merrillite Ca18Na2Mg2(PO4)14 R 3c 3m

38.03.04.05 Merrillite-(Y)* Ca16Y2Mg2(PO4)14 R 3c 3m

38.03.04.06 Ferromerrillite! Ca9NaFe(PO4)7 R 3c 3m

38.03.04.07 Tuite! Ca3(PO4)2 R 3m 3m

38.03.04.08 Bobdownsite! Ca9Mg(PO3F)(PO4)6 R 3c 3m

Strunz Class:

08.AC.45 08 - PHOSPHATES, ARSENATES, VANADATES

08.A - Phosphates, etc. without additional anions, without H2O

08.AC -With medium-sized and large cations

08.AC.45 Merrillite-(Ca)* (Ca,[])19Mg2(PO4)14 R 3c 3m

08.AC.45 Merrillite Ca18Na2Mg2(PO4)14 R 3c 3m

08.AC.45 Merrillite-(Y)* Ca16Y2Mg2(PO4)14 R 3c 3m

08.AC.45 Strontiowhitlockite Sr7(Mg,Ca)3(PO4)6[PO3(OH)] R 3c 3m

08.AC.45 Whitlockite Ca9(Mg,Fe)(PO4)6(PO3OH) R 3c 3m

08.AC.45 Ferromerrillite! Ca9NaFe(PO4)7 R 3c 3m

08.AC.45 Tuite! Ca3(PO4)2 R 3m 3m

08.AC.45 Bobdownsite! Ca9Mg(PO3F)(PO4)6 R 3c 3m

Other Merrillite Information

References:

NAME( Dana8) PHYS. PROP.(Dana8) OPTIC PROP.(Dana8)

See Also:

Links to other databases for Merrillite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - GeoScienceWorld
4 - Google Images
5 - Google Scholar
6 - MinDAT
7 - Mineralienatlas (Deutsch)
8 - Online Mineral Museum
9 - QUT Mineral Atlas
10 - Ruff.Info

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Ask about Merrillite here :
Ask-A-Mineralogist from the Mineralogical Society of America
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Print or Cut-and-Paste your Merrillite Specimen Label here :

Merrillite

Ca18Na2Mg2(PO4)14
Dana No: 38.03.04.04 Strunz No: 08.AC.45
Locality:

Notes: