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Northwest Africa 12692
Basic information Name: Northwest Africa 12692
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 12692
Observed fall: No
Year found: 2019
Country: Mali
Mass:help 373 g
Classification
  history:
Recommended:  LL3.00    [explanation]

This is 1 of 4 approved meteorites classified as LL3.00.   [show all]
Search for other: LL chondrites, LL chondrites (type 3), Ordinary chondrites, and Ordinary chondrites (type 3)
Comments: Approved 3 Aug 2019
Writeuphelp
Writeup from MB 108:

Northwest Africa 12692 (NWA 12692)

Mali

Purchased: March 2019

Classification: Ordinary chondrite (LL3.00)

History: Reportedly found in 2012 by nomads in Mali. Purchased in Morocco, March 2019.

Physical characteristics: Sixteen identically appearing stones with masses ranging from 2-157 g. Exterior surface is desert-weathered with some caliche, no fusion crust. A saw-cut surface reveals many densely packed chondrules, the largest of which is 7 mm in diameter. The largest chondrule (or clast) is irregular in shape and has vesicles. The matrix is black and a few sulfide/metal grains are visible.

Petrography: (C. Agee, UNM) Microprobe examination of a polished mount shows numerous unequilibrated chondrules, apparent mean diameter 600±575 μm (n=47), many with porphyritic, igneous-zoned olivines and pyroxenes, most with glass or mesostasis. Abundant fine-grained matrix is present throughout. Minor metal.

Geochemistry: (C. Agee, UNM) Chondrule olivine Fa12.4±6.5, Fe/Mn=41±20, Cr2O3=0.40±0.11 wt%, n=31; chondrule low-Ca pyroxene Fs3.1±1.8Wo0.7±0.8, Fe/Mn=9±3 n=10. Ferroan chondrules with pyroxenes are rare: most pyroxenes analyzed were in Mg-rich type I chondrules, hence the low Fs mean value.

Classification: Ordinary chondrite (LL3.00). LL based on chondrule size and low abundance of metal. Type 3.00 based on ferroan olivine mean Cr2O3 content and sigma from Grossman and Brearley (2005) and by the presence of S-rich opaque matrix. Comparison of Cr2O3 in ferroan chondrule olivines with those done using the same microprobe and conditions at UNM gave: NWA 7731 (L3.00) Cr2O3=0.43±0.11 wt%, n=98; NWA 8276 (L3.00) Cr2O3=0.42±0.10 wt%; Semarkona (LL3.00) Cr2O3=0.41±0.09 wt%, n=45.

Specimens: 25 g on deposit at CSFK, probe mount at UNM, ZKereszty holds the main mass.

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:
  MB108
  Table 0
  Line 0:
Place of purchase:Morocco
Date:P March 2019
Mass (g):373
Pieces:16
Class:LL3.00
Shock stage:S2
Weathering grade:W2
Fayalite (mol%):12.4±6.5
Ferrosilite (mol%):3.1±1.8
Wollastonite (mol%):0.7±0.8
Classifier:C. Agee, UNM
Type spec mass (g):25
Type spec location:CSFK
Main mass:ZKereszty
Comments:Field name ZK-18; submitted by C. Agee, UNM
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)
ZKereszty: Gyor, Lahner 1. 9024 , Hungary (private address; updated 8 Sep 2014)
CSFK: Research Center for Astronomy and Earth Sciences, H-1121 Budapest, Konkoly Thege Miklós út 15-17.l Hungary, Hungary (institutional address; updated 7 Apr 2015)
Catalogs:
References: Published in Meteoritical Bulletin, no. 108, in preparation (2019)
Find references in NASA ADS:
Find references in Google Scholar:
Photos:
CreditPhotos
Photos uploaded by members of the Encyclopedia of Meteorites.
    (Caution, these are of unknown reliability)
Zsolt Kereszty         
Geography:

Mali
Coordinates:Unknown.

Statistics:
     This is 1 of 32 approved meteorites from Mali (plus 1 unapproved name)

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