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Northwest Africa 10251
Basic information Name: Northwest Africa 10251
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 10251
Observed fall: No
Year found: 2004
Country: (Northwest Africa)
Mass:help 2 kg
Meteoritical Bulletin:  MB 104  (2015)  H3-6
Recommended:  H3-6    [explanation]

This is 1 of 74 approved meteorites classified as H3-6.   [show all]
Search for other: H chondrites, H chondrites (type 3), Ordinary chondrites, and Ordinary chondrites (type 3)
Comments: Approved 28 Aug 2015
Writeup from MB 104:

Northwest Africa 10251 (NWA 10251)

Northwest Africa

Purchased: 2004 Feb

Classification: Ordinary chondrite (H3-6)

History: A single ~2 kg stone was found in a group of stones labeled NWA 869 at the Tucson Gem show in February 2004, purchased by Edwin Thompson, and cut into slices. Multiple slices totaling 257.7 g were donated to Cascadia. A 7.8 g slice was used to make multiple thin sections.

Physical characteristics: Slices are composed dominantly of a host lithology that is medium brown in color and contains abundant metal. Numerous angular black clasts and rounded reddish or light-colored clasts are visible.

Petrography: (M. Hutson and A. Ruzicka, Cascadia) Three serial thin sections expose two black and one round reddish-colored clasts set in a host lithology. The host, best described as a type 3 microbreccia, contains small chondrules (50-300 μm across) and chondrule fragments surrounded by a matrix comprised of angular grain fragments and veins of weathering product and sulfide. Glass, zoned olivine, a silica polymorph, sodalite (one ~60 μm across grain), noticeably abundant merrillite and chlor-apatite, and a large (100 µm across) spinel grain were observed. Most olivine grains show irregular or no fractures with slight to moderate undulose extinction, indicative of shock stage S2. Metal and sulfide show evidence of 20-25% replacement indicative of weathering grade W2. The reddish-colored clast is comprised of distinct chondrules and chondrule fragments, some of which contain twinned low-Ca pyroxene. Large (400-500 µm across) metal grains have scalloped edges and envelope chondrule, olivine, and pyroxene fragments. Shock and weathering are similar to the host. The texture suggests this clast is made of high type 3/low type 4 material. The two black clasts are very different from each other. One is composed primarily of melt-rock with abundant parallel veins and droplets of metal and sulfide that stop abruptly at the clast boundary. One edge of the clast has discernable chondrules, which contain ferrous and magnesian zoned olivine gains (in BSE), suggesting this is a partly melted type 3 clast. The other black clast appears to be a high type 6, with barely discernable chondrules blending into coarse-grained interstitial olivine and pyroxene. The clast contains large (up to 450 µm across) phosphate grains, but no large plagioclase feldspar grains. Instead, feldpathic material occurs in small crystallite-filled pockets between olivine and pyroxene grains and in the numerous sulfide/feldspathic veins that cut across all of the olivine, pyroxene, and phosphate grains in the clast. Olivine grains are difficult to see in transmitted and cross-polarized light. The few that were observable showed deformation consistent with shock stage S5 (planar fractures and strong mosaic extinction).

Geochemistry: Compositions of all measured phases in the host meteorite are variable, and include olivine Fa18.2±4.4 (N=135), low-Ca pyroxene Wo1.1±1.0Fs15.4±4.8 (N=44). In the host lithology, olivine compositions range from Fa1.1 to Fa36.0, with 54 out of 100 grains having compositions (Fa16-20) consistent with an H-group chondrite. Olivine compositions in the reddish clast range from Fa14.5 to Fa23.3, with only 3 out of 19 grains outside of the H-group equilibrated chondrule range. All of the analyzed olivine grains in the high-type black clast are between Fa16.9 and Fa19.7.

Classification: H3-6 fragmental breccia. This rock is clearly not another individual of NWA 869 (L3-6).

Specimens: 249.9 g in six slices, plus three polished thin sections and material in an epoxy stub are on deposit at Cascadia. Patrick Thompson holds the main mass.

Data from:
  Table 0
  Line 0:
Place of purchase:Tucson, USA
Date:P 2004 Feb
Mass (g):2000
Shock stage:S2
Weathering grade:W2
Fayalite (mol%):18.2±4.4
Ferrosilite (mol%):15.4±4.8
Wollastonite (mol%):1.1±1.0
Classifier:A. Ruzicka and M. Hutson, Cascadia
Type spec mass (g):249.9
Type spec location:Cascadia
Main mass:Patrick Thompson
Comments:Lab number CML0341; submitted by A. 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. 104, MAPS 52, 2284, Octover 2017, http://onlinelibrary.wiley.com/doi/10.1111/maps.12930/full
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     This is 1 of 7655 approved meteorites from (Northwest Africa) (plus 1972 unapproved names)

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