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Northwest Africa 12540
Basic information Name: Northwest Africa 12540
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 12540
Observed fall: No
Year found: 2018
Country: (Northwest Africa)
Mass:help 734 g
Meteoritical Bulletin:  MB 108  (2020)  Eucrite-an
Recommended:  Eucrite-an    [explanation]

This is 1 of 15 approved meteorites classified as Eucrite-an.   [show all]
Search for other: Achondrites, Eucrites, and HED achondrites
Comments: Approved 12 Apr 2019
Writeup from MB 108:

Northwest Africa 12540 (NWA 12540)

(Northwest Africa)

Purchased: 2018 Nov

Classification: HED achondrite (Eucrite, anomalous)

History: Purchased by Aziz Habibi in November 2018 from a Mauritanian dealer.

Petrography: (A. Irving and S. Kuehner, UWS; P. Carpenter, WUSL) Recrystallized breccia containing ~8 vol% (estimated from BSE imagery) of Fe-Ni metal (kamacite with taenite). Precursor angular grains of exsolved pigeonite and calcic plagioclase are discernible, but much of the plagioclase has been recrystallized into microgranular aggregates. Accessory phases include silica polymorph, ilmenite and troilite. Magnetic susceptibility log χ (× 10-9 m3/kg) = 4.25 is more than one order of magnitude higher than in the usual eucrites (log χ (× 10-9 m3/kg) = 2.95±0.30, n=70, Rochette et al. 2009) and in agreement with the observed metal content.

Geochemistry: Orthopyroxene host (Fs46.3-48.8Wo4.6-1.6, FeO/MnO = 25-26, N = 3), clinopyroxene exsolution lamellae (Fs19.5-22.9Wo42.7-38.8, FeO/MnO = 23-25, N = 3), plagioclase (An88.3-89.8Or0.3), kamacite (Ni = 4.3 wt.%), taenite (Ni = 51.0 wt.%). Oxygen isotopes (K. Ziegler, UNM): analyses of acid-washed subsamples by laser fluorination gave δ17O 1.778, 1.909, 1.786; δ18O 3.911, 4.120, 3.936; Δ17O -0.287, -0.266, -0.292 per mil.

Classification: Eucrite (anomalous, annealed metal-rich breccia). This specimen has an unusually high amount of Ni-bearing metal and also exhibits extensive post-brecciation annealing textures.

Specimens: 26.8 g including one polished thin section at UWB; remainder with Mr. A. Habibi.

Data from:
  Table 0
  Line 0:
Place of purchase:Mauritania
Date:P 2018 Nov
Mass (g):734
Shock stage:low
Weathering grade:low
Ferrosilite (mol%):46.3-48.8
Wollastonite (mol%):4.6-1.6
Magnetic suscept.:4.25
Classifier:A. Irving, S. Kuehner, UWS; P. Carpenter, WUSL
Type spec mass (g):26.8
Type spec location:UWB
Main mass:A. Habibi
Comments:Work name AH 703; 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)
WUSL: Washington Univ., One Brookings Drive, St. Louis, MO 63130, United States (institutional address; updated 17 Oct 2011)
UWB: University of Washington, Burke Museum of Natural History and Culture, Box 353010 Seattle, WA 98195, United States (institutional address; updated 9 Oct 2023)
References: Published in Meteoritical Bulletin, no. 108 (2020) Meteorit. Planet. Sci. 55, 1146-1150
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Public domain photographs:
A. Irving   

     This is 1 of 9559 approved meteorites from (Northwest Africa) (plus 1872 unapproved names)

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