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Northwest Africa 7812
Basic information Name: Northwest Africa 7812
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 7812
Observed fall: No
Year found: 2013
Country: (Northwest Africa)
Mass:help 46.2 g
Meteoritical Bulletin:  MB 102  (2013)  Angrite
Recommended:  Angrite    [explanation]

This is 1 of 51 approved meteorites classified as Angrite.   [show all]
Search for other: Achondrites, Angrites
Comments: Approved 6 May 2013
Writeup from MB 102:

Northwest Africa 7812 (NWA 7812)

(Northwest Africa)

Purchased: 2013 Mar

Classification: Angrite

History: Purchased by Darryl Pitt in 2013 March from a dealer in Erfoud, Morocco.

Physical characteristics: A single, rounded, black, fine grained stone (46.2 g). A round, smooth-walled vesicle was observed in one interior slice, and a small (stained) olivine xenocryst in another.

Petrography: (A. Irving and S. Kuehner, UWS; C. Agee, UNM) Porphyritic texture. Small, euhedral to subhedral, strongly-zoned olivine phenocrysts (0.3-0.8 mm long) and fairly homogeneous clinopyroxene phenocrysts (up to 0.45 mm long) set in a fine-grained groundmass dominated by bladed grains of kirschsteinite, anorthite, clinopyroxene, ulvöspinel and minor troilite in parallel intergrowth. Olivine phenocrysts exhibit skeletal growth habits, with incomplete closure of crystal domains. An olivine xenocryst contains inclusions of Cr-Al spinel and pentlandite, and is surrounded by olivine phenocrysts nucleated on its margin. Sparse secondary barite is present in the groundmass, and both barite and calcite are present in microfractures in the olivine xenocyst.

Geochemistry: Olivine xenocryst (Fa8.8Ln0.5, FeO/MnO = 175), olivine phenocryst core (Fa14.4Ln0.6, FeO/MnO = 127), olivine phenocryst rim (Fa46.0Ln1.5, FeO/MnO = 112), groundmass kirschsteinite (Fa76.4-79.6Ln8.8-12.2, FeO/MnO = 65-73), clinopyroxene phenocryst core (Fs18.1Wo55.0, FeO/MnO = 112), clinopyroxene phenocryst sector (Fs24.1Wo53.0, FeO/MnO = 84), groundmass clinopyroxene (Fs30.6-32.4Wo51.3-51.8, FeO/MnO = 82-106). Oxygen isotopes (K. Ziegler, UNM) Analysis of acid-washed interior subsamples by laser fluorination gave, respectively (all per mil), δ17O = 2.000, 2.051, 1.957; δ18O = 4.003, 4.068, 3.864; Δ17O = -0.114, -0.097, -0.083 (for a TFL slope of 0.528).

Classification: Achondrite (angrite).

Specimens: 8.9 g of material and one polished thin section are on deposit at UWB; a further 0.4 g and one polished thin section are on deposit at UNM. DPitt holds the main mass.

Data from:
  Table 0
  Line 0:
Place of purchase:Erfoud
Date:P 2013 Mar
Mass (g):46.2
Shock stage:low
Weathering grade:low
Fayalite (mol%):8.8-46.0
Ferrosilite (mol%):18.1-32.4
Wollastonite (mol%):55.0-51.3
Classifier:A. Irving and S. Kuehner, UWS
Type spec mass (g):9.3
Type spec location:8.9 g UWB; 0.4 g UNM
Main mass:D. Pitt
Comments:Submitted by A. Irving
Plots: O isotopes:  
   and collections
UNM: Institute of Meteoritics MSC03 2050 University of New Mexico Albuquerque NM 87131-1126 USA, United States; Website (institutional address; updated 12 Feb 2015)
UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012)
UWB: University of Washington, Burke Museum of Natural History and Culture, Box 353010 Seattle, WA 98195, United States (institutional address; updated 9 Oct 2023)
DPitt: Darryl Pitt, 225 West 83rd Street, New York, NY 10024, United States; Website (private address)
References: Published in Meteoritical Bulletin, no. 102, MAPS 50, 1662, September 2015
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     This is 1 of 9699 approved meteorites from (Northwest Africa) (plus 1854 unapproved names)

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