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Northwest Africa 6991 | |||||||||||||||||||||||||||||||
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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: ![]() | ||||||||||||||||||||||||||||||
Classification history: |
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![]() |
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: MB100 Table 1 Line 1561: |
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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) |
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Catalogs: |
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References: | Published in Meteoritical Bulletin, no. 100, MAPS 49, E1-E101 (2014)
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Geography: |
Statistics: This is 1 of 8904 approved meteorites from (Northwest Africa) (plus 1871 unapproved names) |