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Northwest Africa 12438
Basic information Name: Northwest Africa 12438
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 12438
Observed fall: No
Year found: 2007
Country: (Northwest Africa)
Mass:help 14.4 g
Meteoritical Bulletin:  MB 108  (2020)  Achondrite-ung
Recommended:  Achondrite-ung    [explanation]

This is 1 of 119 approved meteorites classified as Achondrite-ung.   [show all]
Search for other: Achondrites, Ungrouped achondrites
Comments: Approved 11 Jun 2019
Writeup from MB 108:

Northwest Africa 12438 (NWA 12438)

(Northwest Africa)

Purchased: 2007

Classification: Ungrouped achondrite

History: Catalogued at the ROM under M58154.

Physical characteristics: Single stone with a black regmaglypted fusion crust over the exterior.

Petrography: (T.V. Kizovski, ROM) This specimen exhibits a proto-granular texture and is predominantly comprised of euhedral magnesian olivine (60%), with equal amounts of low and high-Ca pyroxenes (39%). Fe-metal fills the grain boundaries between all silicate phases. No feldspar or chondrules are present. The olivine grains vary in size from approximately 300 to 700 µm, and pyroxene grains vary in size from 550 to 800 µm. The stone shows signs of moderate desert weathering, with approximately 60% of metal oxidized. Extensive fracturing is observed in olivine and pyroxene grains with some pyroxenes exhibiting undulatory extinction.

Geochemistry: Mineral compositions and geochemistry: (Y.Liu, UTorG; T.V. Kizovski, ROM) Olivine (Fa3.9±0.6; Fe/Mn = 16.1±2.7; n=27), high-Ca pyroxene (Fs2.7±1.8Wo36.7±0.8; Fe/Mn = 9.1±6.4; n=25), low-Ca pyroxene(Fs4.5±3.1Wo4.3±1.0; Fe/Mn = 13.5±10.0; n=18). Oxygen isotopes (K. Ziegler, UNM): analyses of acid-washed subsamples by laser fluorination gave δ17O = -1.336,-1.469,-1.531; δ18O = 0.943, 0.720, 0.592; Δ17O = -1.834, -1.849, -1.844 per mil. This sample is texturally and chemically similar to ungrouped achondrite NWA 8054, and they may be paired.

Classification: (T.V. Kizovski, ROM) Achondrite (ungrouped)

Specimens: 3.01 g specimen including a thin section and smaller fragments at the ROM. D. DGregory holds the 11.35 g main mass.

Data from:
  Table 0
  Line 0:
Place of purchase:Toronto, Canada
Date:P 2007
Mass (g):14.36
Shock stage:low
Weathering grade:moderate
Fayalite (mol%):3.9±0.6
Ferrosilite (mol%):3.3±2.5
Wollastonite (mol%):21.7±16.1
Classifier:T.V. Kizovski, ROM
Type spec mass (g):3.01
Type spec location:ROM
Main mass:DGregory
Comments:Submitted by T.V. Kizovski, ROM
Plots: O isotopes:  
   and collections
ROM: Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario M5S 2C6, Canada (institutional address; updated 18 Oct 2011)
UNM: Institute of Meteoritics MSC03 2050 University of New Mexico Albuquerque NM 87131-1126 USA, United States; Website (institutional address; updated 12 Feb 2015)
DGregory: David Gregory, 230 First Avenue, Suite 108, St. Thomas, Ontario N5R 4P5, Canada (private address)
UTorG: University of Toronto, Dept. Geology, Earth Sciences Centre, 22 Russell Street Toronto, Ontario, M5S 3B1, Canada (institutional address; updated 31 Jan 2011)
References: Published in Meteoritical Bulletin, no. 108 (2020) Meteorit. Planet. Sci. 55, 1146-1150
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     This is 1 of 8674 approved meteorites from (Northwest Africa) (plus 1882 unapproved names)

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