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Northwest Africa 12774
Basic information Name: Northwest Africa 12774
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 12774
Observed fall: No
Year found: 2019
Country: (Northwest Africa)
Mass:help 454 g
Meteoritical Bulletin:  MB 108  (2020)  Angrite
Recommended:  Angrite    [explanation]

This is 1 of 40 approved meteorites classified as Angrite.   [show all]
Search for other: Achondrites, Angrites
Comments: Approved 3 Aug 2019
Writeup from MB 108:

Northwest Africa 12774 (NWA 12774)

(Northwest Africa)

Purchased: 2019 Jun

Classification: Angrite

History: The stone was purchased by Rachid and Jaouad Chaoui in March 2019 from a Mauritanian dealer, and in June 2019 the main mass was acquired from them at the Ensisheim Show by Marc Jost and Karl Wimmer.

Physical characteristics: A single dark, dense ellipsoidal stone (454 g) lacking fusion crust. The fresh interior exhibits small green crystals within a black matrix.

Petrography: (A. Irving, UWS and P. Carpenter, WUSL) Porphyritic texture. Euhedral, skeletal compositionally-zoned phenocrysts of olivine and subhedral phenocrysts of Al-Ti augite are set within a much finer grained, rapidly-cooled groundmass composed of parallel-grown anorthite, olivine, kirschsteinite and Al-Ti augite together with minor troilite, ulvöspinel and rare spherical grains of kamacite. Subhedral microphenocrysts of chromite are associated with olivine phenocrysts.

Geochemistry: Olivine (cores Fa16.5-18.9Ln0.7, FeO/MnO = 88-111, N = 3; mantles Fa34.1-44.7Ln1.1-1.5, FeO/MnO = 89-100, N = 5; rim Fa69.5Ln4.3, FeO/MnO = 76), olivine in groundmass (Fa76.2Ln4.8, FeO/MnO = 76), Al-Ti augite phenocrysts (Fs17.9-19.5Wo56.4-52.9, FeO/MnO = 64-77, Al2O3 = 17.0-17.7 wt.%, TiO2 = 1.1-1.5 wt.%, N = 3), Al-Ti augite in groundmass (Fs30.3-42.1Wo50.8-53.6, FeO/MnO = 75-120, Al2O3 = 6.3-7.8 wt.%, TiO2 = 2.2-5.3 wt.%, N = 2), anorthite (An99.4-99.7Or0.6-0.3, N = 2), kirschsteinite (Fa61.5-61.7Ln35.5-35.8, FeO/MnO = 68-71, N = 2). Chromite (cores mg 0.53-0.58, cr 0.18-0.23, N = 3; rims mg 0.51-0.54, cr 0.10-0.11, N = 3). Bulk composition (J. Tepper, UPugetSound): analysis of a representative whole rock powder by ICP-OES gave (in wt.%) SiO2 39.4, Al2O3 10.9, CaO 10.9, Na2O 0.32, Mg/(Mg+Fe) = 0.0598.

Classification: Angrite (olivine-phyric). Although texturally similar to NWA 7812, this specimen has different mineral and whole rock compositions, and thus pairing between these stones is ruled out.

Specimens: 22.1 g including one polished thin section and a polished endcut at UWB; the main mass is held jointly by M. Jost and K. Wimmer.

Data from:
  Table 0
  Line 0:
Place of purchase:Ensisheim
Date:P 2019 Jun
Mass (g):454
Shock stage:low
Weathering grade:low
Fayalite (mol%):38.5-76.2
Ferrosilite (mol%):17.9-42.1
Wollastonite (mol%):56.4-50.8
Classifier:A. Irving, UWS, and P. Carpenter, WUSL
Type spec mass (g):22.1
Type spec location:UWB
Main mass:M. Jost/K. Wimmer
Comments:Work name RC113.1; submitted by A. Irving
   and collections
UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012)
WUSL: Washington Univ., One Brookings Drive, St. Louis, MO 63130, United States (institutional address; updated 17 Oct 2011)
UWB: University of Washington, Box 353010 Seattle, WA 98195, United States (institutional address; updated 27 Jul 2012)
References: Published in Meteoritical Bulletin, no. 108 (2020) Meteorit. Planet. Sci. 55, 1146-1150
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     This is 1 of 8904 approved meteorites from (Northwest Africa) (plus 1871 unapproved names)

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