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Northwest Africa 6693
Basic information Name: Northwest Africa 6693
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 6693
Observed fall: No
Year found: 2011
Country: Morocco
Mass:help 5.1 kg
Meteoritical Bulletin:  MB 99  (2012)  Achondrite-ung
Recommended:  Achondrite-ung    [explanation]

This is 1 of 72 approved meteorites classified as Achondrite-ung.   [show all]
Search for other: Achondrites, Ungrouped achondrites
Comments: Approved 6 May 2011
Writeup from MB 99:

Northwest Africa 6693 (NWA 6693)


Found: March 2010

Classification: Ungrouped achondrite

Petrography: The largest pyroxene is poikilitic, 5 mm across, with mainly plagioclase chadacrysts, but pyroxenes with blocky shapes and 1-2 mm maximum dimensions are more common. Olivines are blocky, to 1 mm. Plagioclase is consistently fine-grained and anhedral (interstitial). No chondrules visible. Mineral abundances (vol%) are 70.3 pyroxene, 15.6 olivine, 13.4 plagioclase, 0.6 Cr-spinel, 0.4 Ni-rich metal, ~0.002 Ni-rich sulfide, and trace merrillite.

Geochemistry: The silicate compositions cluster tightly near: low-Ca pyx, En57Wo3.3 with FeO/MnO = 90 (not HED, not martian); feldspar, Ab92Or2.5; olivine Fo47-51. The pyroxene in places contains small lamellae, only rarely (where blebby) large enough for EPMA, of En40Wo40 high-Ca pyroxene. Cr-spinel composition is 57.8 wt% Cr2O3, 32.0 wt% FeO, ~2.1 wt% Fe2O3, 2.8 wt% TiO2, 1.7 wt% MgO. The Ni-rich metal is tightly clustered at 81 wt% Ni. O isotopic composition (B-G. Choi and I. Ahn, using CO2 laser-fluorination at Seoul-NU; avg. of 2 similar replicate analyses): δ18O = 4.32‰, δ17O = 1.19‰ and Δ17O = -1.08‰ (per mil).

Classification: Ungrouped achondrite. No other achondrite has such ferroan mafic silicates (mg~59 low-Ca pyroxene, Fo~50 olivine) in such high modal abundance. The extremely sodic plagioclase (Ab92) and Ni-rich (81 wt%) metal are also distinctive.

Specimens: A 28.4 g type specimen is on deposit at UCLA.

Data from:
  Table 0
  Line 0:
Origin or pseudonym:near Amazraou
Place of purchase:Paris, France
Date:March 2010
Mass (g):5100
Shock stage:S1
Fayalite (mol%):47-51, mean 50
Ferrosilite (mol%):40
Wollastonite (mol%):3
Classifier:Paul Warren
Type spec mass (g):28.4
Type spec location:UCLA
Main mass:Edwin Thompson
Comments:Submitted by Warren
Plots: O isotopes:  
   and collections
UCLA: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095-1567, United States (institutional address; updated 17 Oct 2011)
Seoul-NU: Department of Earth Science Education, Room# 13-426, Seoul National University, Seoul, Korea, 151-748, South Korea (institutional address; updated 20 Dec 2014)
Thompson: Edwin Thompson, 5150 Dawn St., Lake Oswego, OR 97035, United States (private address)
References: Published in Meteoritical Bulletin, No. 99, April 2012, MAPS 47, E1-E52 (2012) [published online only]
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     This is 1 of 1189 approved meteorites from Morocco (plus 11 unapproved names)

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