Meteoritical Bulletin: Entry for Northwest Africa 13257

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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: 1500 g

Classification
history:

Meteoritical Bulletin:	MB 109	(2020)	Martian (shergottite)
Recommended:			Martian (shergottite) [explanation]

This is 1 of 321 approved meteorites (plus 2 unapproved names) classified as Martian (shergottite). [show all]
Search for other: Martian meteorites

Comments:

Approved 5 Apr 2020

Writeup

help

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 (Fs_34.2±8.7Wo_30.9±2.1, range Fs_20.4-46.2Wo_26.5-35.7, FeO/MnO=34±5, n=30) pigeonite (Fs_51.3±5.7Wo_15.0±3.1, range Fs_39.4-61.9Wo_10.7-22.8, FeO/MnO=35±4, n=30) maskelynite (An_47.4±6.9Or_2.4±1.2, range An_34.7-58.7Or_0.5-4.8, 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)

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Photos:

Credit	Photos
Photos uploaded by members of the Encyclopedia of Meteorites. (Caution, these are of unknown reliability)
Antonello Petriccione
Filipe Da Silva de Sousa
Public domain photographs:
Daniel Sheikh

Geography:

Coordinates:

Unknown.

Statistics:
This is 1 of 9699 approved meteorites from (Northwest Africa) (plus 1854 unapproved names)

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Revision
history:

This lists important revisions made to data for this record.

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