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Northwest Africa 8657
Basic information Name: Northwest Africa 8657
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 8657
Observed fall: No
Year found: 2014
Country: (Northwest Africa)
Mass:help 234 g
Classification
  history:
Recommended:  Martian (shergottite)    [explanation]

This is 1 of 159 approved meteorites (plus 1 unapproved name) classified as Martian (shergottite).   [show all]
Search for other: Martian meteorites
Comments: Approved 29 Nov 2014
Writeuphelp
Writeup from MB 103:

Northwest Africa 8657 (NWA 8657)

(Northwest Africa)

Purchased: 2014 Sep

Classification: Martian meteorite (Shergottite)

History: Purchased by Eric Twelker from a Moroccan dealer at the Denver Show in September 2014.

Physical characteristics: Wind-ablated exterior with some small patches of dull black fusion crust. Cut interior surfaces are overall greenish-gray with clear, glassy maskelynite evident, and sporadically distributed dark glass pockets and veinlets

Petrography: (A. Irving and S. Kuehner, UWS) Diabasic texture. Composed predominantly of complexly zoned, prismatically-twinned clinopyroxene (up to 3.8 mm long) and maskelynite laths (up to 1.8 mm long) with accessory ilmenite, ulvöspinel, pyrrhotite, merrillite, chlorapatite and vesicular glass. Minor components are anorthoclase (containing blades of silica polymorph) and symplectitic intergrowths of ferrosilite+silica.

Geochemistry: Subcalcic augite (Fs20.8-21.8Wo36.4-34.1, FeO/MnO = 28-30, N = 2), ferroan subcalcic augite (Fs39.1Wo30.7, FeO/MnO = 39), pigeonite (Fs33.7-53.1Wo11.8-11.6, FeO/MnO = 38-39, N = 2), ferropigeonite rims (Fs65.1-67.1Wo18.7-14.4, FeO/MnO = 37-41, N = 3), ferrosilite (Fs75.4Wo2.0, FeO/MnO = 41), plagioclase (maskelynite) (An42.3-45.3Or2.8-2.7, N = 2), anorthoclase (An33.4Or15.0).

Classification: Martian (shergottite, diabasic). Likely paired with NWA 8656.

Specimens: 20.9 g plus one polished thin section at UWB. The remaining material is held by E. Twelker.

Data from:
  MB103
  Table 0
  Line 0:
Place of purchase:Denver
Date:P 2014 Sep
Mass (g):233.6
Pieces:2
Class:Martian (shergottite)
Shock stage:high
Weathering grade:low
Ferrosilite (mol%):20.8-21.8; 33.7-53.1
Wollastonite (mol%):36.4-34.1; 11.8-11.6
Classifier:A. Irving and S. Kuehner, UWS
Type spec mass (g):20.9
Type spec location:UWB
Main mass:E. Twelker
Comments:ET14-3; submitted by A. Irving
Institutions
   and collections
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)
Twelker: Eric Twelker, P.O. Box 844, Port Townsend, WA 98368, United States; Website (private address; updated 1 Dec 2014)
Catalogs:
References: Published in Meteoritical Bulletin, no. 103, in preparation (2014)
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)
John A. Shea   
Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 5838 approved meteorites from (Northwest Africa) (plus 2066 unapproved names)

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