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| Northwest Africa 11556 | |||||||||||||||||||||||||||||||
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| Basic information | Name: Northwest Africa 11556 This is an OFFICIAL meteorite name. Abbreviation: NWA 11556 Observed fall: No Year found: 2017 Country: (Northwest Africa) Mass:  61 g | ||||||||||||||||||||||||||||||
| Classification history: |
This is 1 of 25 approved meteorites classified as C2-ung. [show all] Search for other: Carbonaceous chondrites, Carbonaceous chondrites (type 2), and Ungrouped chondrites | ||||||||||||||||||||||||||||||
| Comments: | Approved 12 Jan 2018 | ||||||||||||||||||||||||||||||
| Writeup |
Writeup from MB 107:
Northwest Africa 11556 (NWA 11556) (Northwest Africa) Purchased: 2017 Mar Classification: Carbonaceous chondrite (C2, ungrouped) History: Purchased in Agadir, Morocco by Aziz Habibi in March 2017. Physical characteristics: A single, very soft jet black stone (61 g) containing some visible but tiny, clear crystalline objects. During preparation for powder X-ray diffraction by immersing sample fines in methanol a strong organic odor was emitted. Petrography: (A. Irving and S. Kuehner, UWS; L. Garvie, ASU) Sparse very small, subspherical polycrystalline objects (apparent diameter 180±150 µm, N = 18) and angular mafic silicate mineral grains are set in a very fine grained matrix. The dominant matrix (~90 vol.%, jet black in thin section) contains prominent open shrinkage cracks and is composed mainly of indeterminate mafic silicates plus minor chromite, pentlandite and calcite. X-ray diffraction shows the specimen to be dominated by tochilinite and well-crystallized serpentine. No CAI were observed despite a careful search. Geochemistry: Olivine (Fa1.2-56.0, Cr2O3 in ferroan examples 0.10-0.40 wt.%, mean 0.25±0.11 wt.%, N = 8), orthopyroxene (Fs0.9-1.0Wo1.0-3.6, N = 3), clinopyroxene (Fs1.1Wo42.2; Fs0.9Wo48.0; N = 2). Oxygen isotopes (K. Ziegler, UNM): analyses of untreated subsamples by laser fluorination gave, respectively, δ17O -2.789, -3.797; δ18O 1.421, -0.319; Δ17O -3.539, -3.629 per mil. Classification: Carbonaceous chondrite (type 2, ungrouped). The paucity of chondrule-like objects, high abundance of matrix, and more 16O-rich bulk oxygen isotope composition distinguish this specimen from CM chondrites. Specimens: 12.3 g including one polished thin section at UWB; remainder with Mr. A. Habibi. | ||||||||||||||||||||||||||||||
| Data from: MB107 Table 0 Line 0: |
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| Plots: | O isotopes: | ||||||||||||||||||||||||||||||
| Institutions and collections |
ASU: Center for Meteorite Studies, Arizona State University, Tempe, Arizona 85287-1404, United States; Website (institutional address; updated 14 Jan 2012) UNM: Institute of Meteoritics MSC03 2050 University of New Mexico Albuquerque NM 87131-1126 USA, United States; Website (institutional address; updated 12 Feb 2015) 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, Burke Museum of Natural History and Culture, Box 353010 Seattle, WA 98195, United States (institutional address; updated 9 Oct 2023) |
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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) | ||||||||||||||||||||||||||||||