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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
Classification
  history:
Meteoritical Bulletin:  MB 103  (2014)  Diogenite
Recommended:  Diogenite    [explanation]

This is 1 of 420 approved meteorites classified as Diogenite.   [show all]
Search for other: Achondrites, Diogenites, and HED achondrites
Comments: Approved 6 Sep 2014
Writeuphelp
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:
  MB103
  Table 0
  Line 0:
State/Prov/County:Saguia el Hamra
Date:2013 Mar
Latitude:27.307°N
Longitude:12.083°W
Mass (g):>20000
Pieces:1
Class:Diogenite
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:  
Institutions
   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, Box 353010 Seattle, WA 98195, United States (institutional address; updated 27 Jul 2012)
Catalogs:
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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Photos:
CreditPhotos
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    (Caution, these are of unknown reliability)
Aeroliths Collection Theodossiou         
Alessandro Takeda   
Bruno Caspirro   
Charley Kettel   
Cosimo Damiano Gorgoglione   
Dave Johnson   
Denis gourgues            
Franco Vignato      
John A. Shea      
John Tanner   
José Carlos de Medeiros Júnior   
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MCMcanarias   
Meteor-Center   
Michael S. Scherman   
Mike Markowitz   
Piotr gural100   
Russ Opdahl      
Wang Ziyao            
Woreczko Jan & Wadi            
Geography:

Western Sahara
Coordinates:
     Recommended::   (27° 18' 25"N, 12° 4' 59"W)

Statistics:
     This is 1 of 78 approved meteorites from Saguia el Hamra, Western Sahara
     This is 1 of 198 approved meteorites from Western Sahara (plus 19 unapproved names)
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