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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
Meteoritical Bulletin:  MB 103  (2014)  Martian (shergottite)
Recommended:  Martian (shergottite)    [explanation]

This is 1 of 326 approved meteorites (plus 2 unapproved names) classified as Martian (shergottite).   [show all]
Search for other: Martian meteorites
Comments: Approved 29 Nov 2014
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:
  Table 0
  Line 0:
Place of purchase:Denver
Date:P 2014 Sep
Mass (g):233.6
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
   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, Burke Museum of Natural History and Culture, Box 353010 Seattle, WA 98195, United States (institutional address; updated 9 Oct 2023)
Twelker: Eric Twelker, P.O. Box 844, Port Townsend, WA 98368, United States; Website (private address; updated 1 Dec 2014)
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 uploaded by members of the Encyclopedia of Meteorites.
    (Caution, these are of unknown reliability)
John A. Shea   

     This is 1 of 9790 approved meteorites from (Northwest Africa) (plus 1854 unapproved names)

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