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Northwest Africa 8640
Basic information Name: Northwest Africa 8640
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 8640
Observed fall: No
Year found: 2005
Country: (Northwest Africa)
Mass:help 4.21 kg
Meteoritical Bulletin:  MB 103  (2014)  Eucrite-pmict
Recommended:  Eucrite-pmict    [explanation]

This is 1 of 393 approved meteorites classified as Eucrite-pmict.   [show all]
Search for other: Achondrites, Eucrites, and HED achondrites
Comments: Approved 25 Nov 2014
Writeup from MB 103:

Northwest Africa 8640 (NWA 8640)

(Northwest Africa)

Purchased: 2005 Jan

Classification: HED achondrite (Eucrite, polymict)

History: Purchased by Dr. David Gregory from a Moroccan dealer in January 2005.

Petrography: (A. Irving and S. Kuehner, UWS) Polymict breccia composed predominantly of clasts of basaltic, diabasic and gabbroic eucrite, all of which contain clinopyroxene that is pale clove brown in thin section. In most clasts both the pyroxene and calcic plagioclase are polycrystalline, but in some clasts they are not. Accessory minerals in eucrite clasts are silica polymorph, ilmenite, Ti-chromite, troilite and stained Ni-free metal. Diogenitic orthopyroxene is present as sparse grains (< 1 vol.%). Some thin veinlets of secondary calcite are present.

Geochemistry: Diogenitic orthopyroxene (Fs30.0Wo3.40, FeO/MnO = 35), host orthopyroxene (Fs57.7-60.1Wo4.0-2.8, FeO/MnO = 32-33, N = 3), clinopyroxene exsolution lamellae (Fs36.2-39.9Wo25.9-23.6, FeO/MnO = 31-33, N = 3), pigeonite (Fs41.1Wo20.6, FeO/MnO = 32).

Classification: Eucrite (polymict).

Specimens: 22 g including two polished thin sections at UWB. The remainder is held by DGregory.

Data from:
  Table 0
  Line 0:
Place of purchase:Morocco
Date:P 2005 Jan
Mass (g):4210
Shock stage:moderate
Weathering grade:low
Ferrosilite (mol%):30.0; 57.7-60.1; 36.2-39.
Wollastonite (mol%):3.40; 4.0-2.8; 25.9-23.6
Classifier:A. Irving and S. Kuehner, UWS
Type spec mass (g):22
Type spec location:UWB
Main mass:DGregory
Comments:DG14-2; 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, Box 353010 Seattle, WA 98195, United States (institutional address; updated 27 Jul 2012)
DGregory: David Gregory, 230 First Avenue, Suite 108, St. Thomas, Ontario N5R 4P5, Canada (private address)
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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     This is 1 of 9013 approved meteorites from (Northwest Africa) (plus 1869 unapproved names)

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