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Northwest Africa 7831
Basic information Name: Northwest Africa 7831
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 7831
Observed fall: No
Year found: 2013
Country: Western Sahara
Mass:help 20 kg
Meteoritical Bulletin:  MB 103  (2014)  Diogenite
Recommended:  Diogenite    [explanation]

This is 1 of 524 approved meteorites (plus 2 unapproved names) classified as Diogenite.   [show all]
Search for other: Achondrites, Diogenites, and HED achondrites
Comments: Approved 6 Sep 2014
Writeup from MB 103:

Northwest Africa 7831 (NWA 7831)        27.307°N, 12.083°W

Saguia el Hamra, Western Sahara

Found: 2013 Mar

Classification: HED achondrite (Diogenite)

History: Found buried in the ground near Chouichiyat on March 3, 2013, and excavated by a team of local people.

Physical characteristics: A single large mass (at least 20 kg) composed of yellow-green crystalline material with pale orange weathering products along numerous fractures. Much of the material disintegrated into fragments upon excavation.

Petrography: (A. Irving and S. Kuehner, UWS) The specimen is composed almost entirely of translucent, yellow-green orthopyroxene with very sparse, tiny included grains of Ni-free metal, troilite, chromite, anorthite, silica polymorph and clinopyroxene. Secondary pale orange, clay-like deposits from terrestrial weathering are present along thin fractures.

Geochemistry: Orthopyroxene (Fs28.1-28.3Wo3.0-3.3; FeO/MnO = 29-31), clinopyroxene (Fs10.9Wo43.1, FeO/MnO = 26). Oxygen isotopes (K. Ziegler, UNM): analyses of acid-washed orthopyroxene by laser fluorination gave, respectively, δ17O = 1.677, 1.793, 1.810; δ18O = 3.680, 3.879, 3.875; Δ17O = -0.266, -0.255, -0.236 per mil.

Specimens: 44.5 g of material is on deposit at UWB. The remainder is held by several anonymous collectors.

Data from:
  Table 0
  Line 0:
State/Prov/County:Saguia el Hamra
Date:2013 Mar
Mass (g):>20000
Shock stage:low
Weathering grade:moderate
Ferrosilite (mol%):see text
Classifier:A. Irving and S. Kuehner, UWS
Type spec mass (g):45.4
Type spec location:UWB
Main mass:Anonymous
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)
References: Published in Meteoritical Bulletin, no. 103, MAPS 52, 1014, May 2017, http://onlinelibrary.wiley.com/doi/10.1111/maps.12888/full
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Western Sahara
     Recommended::   (27° 18' 25"N, 12° 4' 59"W)

     This is 1 of 117 approved meteorites from Saguia el Hamra, Western Sahara (plus 1 unapproved name)
     This is 1 of 283 approved meteorites from Western Sahara (plus 20 unapproved names)
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