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Northwest Africa 8257
Basic information Name: Northwest Africa 8257
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 8257
Observed fall: No
Year found: 2013
Country: (Northwest Africa)
Mass:help 17.45 kg
Classification
  history:
Meteoritical Bulletin:  MB 104  (2015)  L3
Recommended:  L3.15    [explanation]

This is 1 of 6 approved meteorites classified as L3.15.   [show all]
Search for other: L chondrites, L chondrites (type 3), Ordinary chondrites, and Ordinary chondrites (type 3)
Comments: Approved 10 Dec 2015
Revised 23 Jun 2019: subtype added
Writeuphelp
Writeup from MB 104:

Northwest Africa 8257 (NWA 8257)

(Northwest Africa)

Purchased: 2013 Dec

Classification: Ordinary chondrite (L3)

History: Purchased by Darryl Pitt in December 2013 from a dealer in Erfoud, Morocco.

Petrography: (A. Irving and S. Kuehner, UWS) Closely packed, well-formed, glass-bearing chondrules are set in a sparse finer grained matrix.

Geochemistry: Olivine (Fa0.5-72.9; Cr2O3 in ferroan examples ranges from 0.06-0.52 wt.%, mean 0.18±0.17 wt.%, N = 13), orthopyroxene (Fs2.2-19.9Wo0.3-4.9, N = 3), subcalcic augite (Fs10.9Wo35.9; Fs22.3Wo24.9). Oxygen isotopes (K. Ziegler, UNM): analyses of three acid-washed subsamples by laser fluorination gave, respectively, δ17O 2.950, 3.615, 3.246; δ18O 4.356, 4.840, 4.723; Δ17O 0.650, 1.059, 0.752 per mil.

Classification: Ordinary chondrite (L3). The wide range in Fa content in olivine coupled with the range of Cr content in ferroan olivine imply a very low subtype <3.2.

Specimens: 38 g including one polished thin section at UWB; the remainder is held by DPitt.


Writeup from MB 108:
NWA 8257: petrologic subtype

J. Boesenberg, Brown, and S. Kuehner, UWS, find that NWA 8257 has a Cr2O3 content of ferroan olivine of 0.04-1.02 wt.%, mean 0.22±0.24 wt.%, N = 30. The range and mean of Cr content in ferroan olivine is consistent with a subtype of 3.15 (per Grossman and Brearley, 2005, Fig. 15a).
Bibliography:
  • Grossman J.N. and Brearley A.J. (2005) The onset of metamorphism in ordinary and carbonaceous chondrites. Meteorit. Planet. Sci. 40, 87-122. (link)
Data from:
  MB104
  Table 0
  Line 0:
Place of purchase:Erfoud
Date:P 2013 Dec
Mass (g):17450
Pieces:1
Class:L3
Shock stage:S2
Weathering grade:W1
Fayalite (mol%):0.5-72.9
Ferrosilite (mol%):2.2-19.9
Wollastonite (mol%):0.3-4.9
Magnetic suscept.:4.83
Classifier:A. Irving and S. Kuehner, UWS
Type spec mass (g):38
Type spec location:UWB
Main mass:D. Pitt
Comments:DP14-1; submitted by A. Irving
Plots: O isotopes:  
Institutions
   and collections
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)
DPitt: Darryl Pitt, 225 West 83rd Street, New York, NY 10024, United States; Website (private address)
Catalogs:
References: Published in Meteoritical Bulletin, no. 104, MAPS 52, 2284, Octover 2017, http://onlinelibrary.wiley.com/doi/10.1111/maps.12930/full
Published in Meteoritical Bulletin, no. 108, in preparation (2019)
Find references in NASA ADS:
Find references in Google Scholar:
Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 7035 approved meteorites from (Northwest Africa) (plus 2000 unapproved names)

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