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Northwest Africa 6991
Basic information Name: Northwest Africa 6991
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 6991
Observed fall: No
Year found: 2010
Country: (Northwest Africa)
Mass:help 487 g
Meteoritical Bulletin:  MB 100  (2012)  CV3
Recommended:  CV3    [explanation]

This is 1 of 602 approved meteorites (plus 1 unapproved name) classified as CV3.   [show all]
Search for other: Carbonaceous chondrites, Carbonaceous chondrites (type 3), CV chondrites, and CV-CK clan chondrites
Comments: Approved 24 Oct 2011
Writeup from MB 100:

Northwest Africa 6991 (NWA 6991)

(Northwest Africa)

Purchased: June 2010

Classification: Carbonaceous chondrite (CV3)

Physical characteristics: Single 487 g, potato-shaped stone. Fusion crust on one side of stone. Interior of the stone fresh.

Petrography: (Laurence Garvie, ASU) Section dominated by large (0.1 to 9 mm, mean ~ 1mm) FeO poor chondrules set in a fine-grained matrix. No type-II chondrules found. Chondrule types include granular, POP, PO, BO, and rare small (100 μm) RP. AOAs to 3 × 1 mm. Meteorite contains one large (2 cm) coarse-grained type B CAI dominated by spinel, anorthite, melilite, and fassaite.

Geochemistry: (Laurence Garvie, ASU) Olivines show two compositional ranges - Fa0.3-2.2 in granular, PO, and POP (mean Fa0.7, n=13, with up to 0.6 wt% Cr2O3), and Fa7.2-8.2 (n=3) in BO. Pyroxene represented by low Ca-pyroxene (Fs0.7-1.1Wo0.8-1.1) and augite Fs1.2-1.7Wo25.5-43.2 (with up to 5.4 wt% Al2O3). Minor phases include isolated subhedral fayalite (Fa~100) grains to 100 μm in the matrix (there are ~20 such grains in the thin section). Magnetite abundant in the matrix. Fe-Ni metal rare, Ni-rich Fe sulfide common.

Classification: CV3 oxidized subgroup based on the abundance of magnetite and Ni-rich Fe sulfides and rarity of Fe-Ni metal.

Data from:
  Table 1
  Line 1561:
Place of purchase:Saint Marie, France
Date:P June 2010
Mass (g):487
Shock stage:low
Weathering grade:low
Fayalite (mol%):0.3-8.2
Ferrosilite (mol%):0.7-1.1
Wollastonite (mol%):0.8-1.1
Classifier:Laurence Garvie, ASU
Type spec mass (g):47
Type spec location:ASU
Main mass:MFarmer
Comments:Submitted by Laurence Garvie
   and collections
ASU: Center for Meteorite Studies, Arizona State University, Tempe, Arizona 85287-1404, United States; Website (institutional address; updated 14 Jan 2012)
MFarmer: Michael Farmer, P.O. Box 86059, Tucson, AZ 85754-6059, United States; Website (private address)
References: Published in Meteoritical Bulletin, no. 100, MAPS 49, E1-E101 (2014)
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     This is 1 of 8904 approved meteorites from (Northwest Africa) (plus 1871 unapproved names)

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