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Northwest Africa 15931
Basic information Name: Northwest Africa 15931
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 15931
Observed fall: No
Year found: 2016
Country: (Northwest Africa)
Mass:help 118 g
Meteoritical Bulletin:  MB 112  (2024)  E6
Recommended:  E6    [explanation]

This is 1 of 10 approved meteorites classified as E6.   [show all]
Search for other: Enstatite chondrites, Enstatite chondrites (type 4-7), and Enstatite-rich meteorites
Comments: Approved 29 Sep 2023
Writeup from MB 112:

Northwest Africa 15931 (NWA 15931)

(Northwest Africa)

Purchased: 2016 Apr

Classification: Enstatite chondrite (E6)

History: A 47 g end piece of the meteorite was sent to Cascadia by John Shea, who purchased the sample on April 2016 from Arizona Meteorites via ebay. The ebay listing stated that the meteorite was found in Morocco, but also that the provenance that was sent with the meteorite stated that it was found in Algeria in 2000. On January 19, 2021, Martin Goff emailed Cascadia that he had "recently acquired a box of NWA Chondrites that came from US collector john/Johannes Shea", including CML 0912.

Physical characteristics: Physical Characteristics: Cascadia received an end cut with a brown irregular exterior from which material flakes off. The cut face is light brown with extensive darker brown veining.

Petrography: (M. Hutson, A. Ruzicka, Cascadia): The thin section is substantially dark in plane-polarized light due to extensive veining by iron oxide/hydroxide weathering product, and contains two large (2 mm and 3 mm across) holes containing terrestrial infill. In BSE, the sample is composed mainly of coarse-grained enstatite and feldspar. Phases observed in BSE and confirmed by chemical analysis are enstatite, albitic feldspar (examined grains which appear to be single grains crossed by numerous weathering veins are ~50 µm across) schreibersite, remnant troilite grains containing thin lamellae and blocky grains of daubréelite, and an SiO2 polymorph. No olivine was observed. No metal has survived terrestrial weathering.

Geochemistry: Low-Ca pyroxene: En97.7±0.3Fs0.9±0.3Wo1.4±0.04, N=24; Plagioclase feldspar: Ab79.5±0.7An16.0±0.5Or4.5±0.4, N=15.

Classification: Enstatite chondrite (E6) based on mineral chemistry and texture. Because of the absence of metal, that has been entirely turned into oxide/hydroxide weathering products, it is not possible to assigne a EH or EL classification to this meteorite.

Specimens: Cascadia holds 45.7 g in one piece, as well as a polished thin section and material in an epoxy butt.

Data from:
  Table 0
  Line 0:
Place of purchase:ebay
Date:P 2016 Apr
Mass (g):118
Weathering grade:high
Ferrosilite (mol%):0.9±0.3 (N=24)
Wollastonite (mol%):1.4±0.04 (N=24)
Classifier:M. Hutson, K. Malacara, and A. Ruzicka, Cascadia
Type spec mass (g):47
Type spec location:Cascadia
Main mass:MGoff (Martin Goff, MSG Meteorites, United Kingdom; http://www.msg-meteorites.co.uk/)
Comments:Lab number CML 0912; submitted by Melinda Hutson
   and collections
Cascadia: Cascadia Meteorite Laboratory, Portland State University, Department of Geology, Room 17 Cramer Hall, 1721 SW Broadway, Portland, OR 97201, United States; Website (institutional address; updated 28 Oct 2011)
References: Published in Gattacceca J., McCubbin F. M., Grossman J. N., Schrader D. L., Cartier C., Consolmagno G., Goodrich C., Greshake A., Gross J., Joy K. H., Miao B. and Zhang B. (2024) The Meteoritical Bulletin, no. 112. Meteoritics & Planetary Science 59, 1820–1823. ?
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     This is 1 of 9790 approved meteorites from (Northwest Africa) (plus 1854 unapproved names)

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