Meteoritical Bulletin: Entry for Northwest Africa 6991

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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: 487 g

Classification
history:

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

help

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 - Fa_0.3-2.2in granular, PO, and POP (mean Fa_0.7, n=13, with up to 0.6 wt% Cr₂O₃), and Fa_7.2-8.2(n=3) in BO. Pyroxene represented by low Ca-pyroxene (Fs_0.7-1.1Wo_0.8-1.1) and augite Fs_1.2-1.7Wo_25.5-43.2(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:
  MB100
  Table 1
  Line 1561:

Place of purchase:	Saint Marie, France
Date:	P June 2010
Mass (g):	487
Pieces:	1
Class:	CV3
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

Institutions
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)

Catalogs:

References:

Published in Meteoritical Bulletin, no. 100, MAPS 49, E1-E101 (2014)

Find references in NASA ADS:
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Geography:

Coordinates:

Unknown.

Statistics:
This is 1 of 8904 approved meteorites from (Northwest Africa) (plus 1871 unapproved names)

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