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Northwest Africa 11991 | |||||||||||||||||||||||||||
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Basic information | Name: Northwest Africa 11991 This is an OFFICIAL meteorite name. Abbreviation: NWA 11991 Observed fall: No Year found: 2018 Country: (Northwest Africa) Mass: ![]() | ||||||||||||||||||||||||||
Classification history: |
This is 1 of 469 approved meteorites classified as LL3. [show all] Search for other: LL chondrites, LL chondrites (type 3), Ordinary chondrites, and Ordinary chondrites (type 3) | ||||||||||||||||||||||||||
Comments: | Approved 9 Oct 2018 | ||||||||||||||||||||||||||
Writeup![]() |
Writeup from MB 107:
Northwest Africa 11991 (NWA 11991) (Northwest Africa) Purchased: 2018 Jan Classification: Ordinary chondrite (LL3) History: Found in northwest Africa. Physical characteristics: In cut slices, interior is light gray to light brown with slight weathering staining, has well defined chondrules and metal contents typical of LL chondrites. Petrography: (A. Ruzicka, S. Goudy, Cascadia) Thin section shows well-defined chondrules, many with glassy mesostases, and good examples of cluster chondrite texture with little intervening matrix. Multiple bleached chondrules. Analysis in reflected light shows thin section contains roughly 2.3% metal with ~10% metal weathered, and roughly 4.2% troilite; largest slice contains 2.8±0.3% metal and 5.4±0.6% troilite (area% values). Based on olivine, shock stage is S5. Matrix is composed chiefly of <10 μm grains of ferroan olivine and albitic feldspar, reminiscent of that found in Lut 005 and Lut 006. Geochemistry: (M. Hutson, Cascadia) Olivine (Fa21.6±9.9, N = 156; Cr2O3 0.07±0.05 wt%, N = 126). Classification: LL3, estimated subtype 3.5. LL indicated by low metal content and minor weathering. Type 3 indicated by texture, presence of chondrule glass, and variable olivine composition. Subtype estimated as 3.5 based on olivine Fa variability (subtype 3.4-3.6) and chrome content in olivine. Specimens: A total of 48.4 g in two slices, a polished thin section, and potted butt are available at Cascadia. Mr. James Tobin holds the main mass. | ||||||||||||||||||||||||||
Data from: MB107 Table 0 Line 0: |
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Institutions 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) Tobin: J. Tobin, The Meteorite Exchange, PMB #455, P.O. Box 7000, Redondo Beach, CA 90277, United States (private address) |
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Catalogs: |
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References: | Published in Meteoritical Bulletin, no. 107, MAPS 55, 460-462
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Geography: |
Statistics: This is 1 of 9429 approved meteorites from (Northwest Africa) (plus 1876 unapproved names) |