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Northwest Africa 13257
Basic information Name: Northwest Africa 13257
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 13257
Observed fall: No
Year found: 2018
Country: (Northwest Africa)
Mass:help 1500 g
Classification
  history:
Recommended:  Martian (shergottite)    [explanation]

This is 1 of 252 approved meteorites (plus 1 unapproved name) classified as Martian (shergottite).   [show all]
Search for other: Martian meteorites
Comments: Approved 5 Apr 2020
Writeuphelp
Writeup from MB 109:

Northwest Africa 13257 (NWA 13257)

(Northwest Africa)

Purchased: 2018

Classification: Martian meteorite (Shergottite)

History: Purchased in 2018 by Daoud Wabich from a meteorite dealer in Algeria.

Physical characteristics: Multiple stones with weathered fusion crust.

Petrography: (D. Sheikh, FSU) Sample is a diabase having a predominantly subophitic texture composed of zoned, tabular and prismatic (sometimes twinned) chadacrysts of subcalcic augite and pigeonite (Av. 600±50 µm, up to 1 mm, 58 vol%) contained within larger oikocrysts of maskelynite (Av. 800±50µm, up to 2mm, 42 vol%). Accessory phases include titanomagnetite (some Cr rich), silica, Si-Al-K-Na rich glass, merrillite, chlorapatite, and pyrrhotite. Sample contains minor carbonate weathering veins.

Geochemistry: Subcalcic augite (Fs34.2±8.7 Wo30.9±2.1, range Fs20.4-46.2Wo26.5-35.7, FeO/MnO=34±5, n=30) pigeonite (Fs51.3±5.7Wo15.0±3.1, range Fs39.4-61.9Wo10.7-22.8, FeO/MnO=35±4, n=30) maskelynite (An47.4±6.9Or2.4±1.2, range An34.7-58.7Or0.5-4.8, n=26).

Classification: Martian (shergottite, diabasic) Silicate chemistry, the presence of maskelynite, FeO/MnO ratios of pyroxenes, and magnetic susceptibility provide support for classification as shergottite. Average grain sizes of pyroxenes and maskelynite larger than that of basaltic shergottites, but smaller than gabbroic shergottites, hence diabasic.

Specimens: 21.3 grams at UCLA; main mass with Daoud Wabich.

Data from:
  MB109
  Table 0
  Line 0:
Place of purchase:Algeria
Date:P 2018
Mass (g):1500
Pieces:10
Class:Martian (shergottite)
Shock stage:high
Weathering grade:moderate
Ferrosilite (mol%):51.3±5.7, 34.2±8.7
Wollastonite (mol%):15.0±3.1, 30.9±2.1
Magnetic suscept.:3.52
Classifier:D. Sheikh, FSU
Type spec mass (g):21.3
Type spec location:UCLA
Main mass:Daoud Wabich
Comments:Submitted by Daniel Sheikh
Institutions
   and collections
UCLA: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095-1567, United States (institutional address; updated 17 Oct 2011)
FSU: Department of Geological Sciences, Florida State University, Tallahassee FL 32306-4100, United States (institutional address; updated 16 Dec 2010)
Catalogs:
References: Published in Meteoritical Bulletin, no. 109, in preparation (2020)
Find references in NASA ADS:
Find references in Google Scholar:
Photos:
CreditPhotos
Photos uploaded by members of the Encyclopedia of Meteorites.
    (Caution, these are of unknown reliability)
Antonello Petriccione   
Public domain photographs:
Daniel Sheikh   
Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 7727 approved meteorites from (Northwest Africa) (plus 1972 unapproved names)

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