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Northwest Africa 11556
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:help 61 g
Classification
  history:
Recommended:  C2-ung    [explanation]

This is 1 of 19 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
Writeuphelp
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:
Place of purchase:Agadir
Date:P 2017 Mar
Mass (g):61
Pieces:1
Class:C2-ung
Shock stage:S1
Weathering grade:low
Fayalite (mol%):1.2-51.0
Ferrosilite (mol%):0.9-1.0
Wollastonite (mol%):1.0-3.6
Classifier:A. Irving and S. Kuehner, UWS
Type spec mass (g):12.3
Type spec location:UWB
Main mass:A. Habibi
Comments:Work name AH17-30; submitted by A. Irving
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, Box 353010 Seattle, WA 98195, United States (institutional address; updated 27 Jul 2012)
Catalogs:
References: Published in Meteoritical Bulletin, no. 107, in preparation (2018)
Find references in NASA ADS:
Find references in Google Scholar:
Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 6759 approved meteorites from (Northwest Africa) (plus 2047 unapproved names)

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