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Northwest Africa 8231
Basic information Name: Northwest Africa 8231
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 8231
Observed fall: No
Year found: 2005
Country: (Northwest Africa)
Mass:help 356 g
Meteoritical Bulletin:  MB 103  (2014)  H4-6
Recommended:  H4-6    [explanation]

This is 1 of 114 approved meteorites classified as H4-6.   [show all]
Search for other: H chondrites, H chondrites (type 4-7), Ordinary chondrites, and Ordinary chondrites (type 4-7)
Comments: Approved 1 Feb 2014
Writeup from MB 103:

Northwest Africa 8231 (NWA 8231)

(Northwest Africa)

Purchased: Oct. 2005

Classification: Ordinary chondrite (H4-6)

History: A single stone of 356 g, supposedly found south of Zagora, Morocco, was obtained by Edwin Thompson from a trader in October 2005. A 28 g slice and crumbs from this stone were donated by Thompson to Cascadia on Dec. 13, 2005, and the remaining available mass (325.1 g in two pieces) was purchased from Patrick Thompson on Aug. 15, 2013.

Physical characteristics: The specimen has a largely fusion crusted surface that appears brown-gray with reddish weathering patches. Cut surfaces show an interior with irregularly-shaped light-colored inclusions and brown-stained host with a breccia texture and some thin shock veins.

Petrography: (K. Armstrong and A. Ruzicka, Cascadia) The host has a brecciated, chondritic texture and appears "blackened" in transmitted light caused by the presence of fine-grained troilite and metal and weathering product. Chondrule size is 0.6±0.2 mm (N = 26), with chondrules more distinct in some regions than others. Some feldspar grains are >50 μm across but most feldspar is finer-grained. Larger metal and troilite grains comprise 6.5±0.6 and 5.3±0.3 area% of the host, respectively, determined by pixel counting in reflected light images.

Geochemistry: Mineral compositions and geochemistry: Representative olivine is Fa19.4±0.4, and Fe/Mn = 38.6±7.5 (N = 37). Low-Ca pyroxene is Fs17.2±0.3Wo1.2±0.1 (N = 25). A small amount of slightly magnesian olivine and pyroxene grains were noted in BSE images.

Classification: Mineral chemistry and textures point to a dominance of H5 material, but the meteorite appears to be an H4-6 breccia based on the presence of some regions with poorly-defined chondrules and coarse feldspar, and the rare occurrence of slightly magnesian olivine and pyroxene grains. The meteorite was extensively shock-blackened.

Specimens: Type specimens at Cascadia include the main mass (284.2 g), five separate cut pieces totaling 59.2 g, and a polished thin section and potted butt.

Data from:
  Table 0
  Line 0:
Place of purchase:Munich, Germany
Date:P Oct. 2005
Mass (g):356
Shock stage:S3
Weathering grade:W2
Fayalite (mol%):19.4±0.4
Ferrosilite (mol%):17.2±0.3
Wollastonite (mol%):1.2±0.1
Classifier:K. Armstrong and A. Ruzicka, Cascadia
Type spec mass (g):343.6
Type spec location:Cascadia
Main mass:Cascadia
Comments:Lab sample number CML 0368; submitted by Alex Ruzicka
   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)
Thompson: Edwin Thompson, 5150 Dawn St., Lake Oswego, OR 97035, United States (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 9776 approved meteorites from (Northwest Africa) (plus 1862 unapproved names)

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