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Northwest Africa 6698
Basic information Name: Northwest Africa 6698
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 6698
Observed fall: No
Year found: 2010
Country: Morocco
Mass:help 38.4 g
Meteoritical Bulletin:  MB 99  (2011)  Achondrite-ung
Recommended:  Achondrite-ung    [explanation]

This is 1 of 84 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 6698 (NWA 6698)


Found: 2009

Classification: Ungrouped achondrite

History: A 38.4 g stone found October 2009 was purchased from a dealer in Erfoud, Morocco, in 2010.

Physical characteristics: No fusion crust. Surface is lightly weathered, but heavily desert wind-ablated.

Petrography: (T. Bunch and J. Wittke, NAU; A. Irving, UWS): Fine to medium grained (<2 mm) dioritic rock that contains 69 vol. % plagioclase, 27 vol. %, pyroxenes (augite and pigeonite), and 4 vol. % accessory phases (taenite, chromite, chlorapatite and FeS). Plagioclase displays simple albite and Carlsbad twinning, is mostly equigranular, and contains included pyroxene chadacrysts. Pyroxenes are dominantly augite and unexsolved pigeonite with highly variable grain size, and contain included plagioclase chadacrysts. Sparse pockets of brown, glassy late-stage residuum with microlites are present between the other phases. Shock level is low to moderate, with undulatory extinction in plagioclase and some pyroxenes. Interior weathering is low.

Geochemistry: Most plagioclase shows a range in composition An22.4-36Or2.2, with a few zoned grains with cores of An52-56Or2.1 to rims of An36; residuum albite, An10Or5.7. Augite, Fs18.5-27.0Wo36.7-41.2 (FeO/MnO = 14-17), Al2O3 = 2.2 wt%, Na2O = 1.2 wt%; TiO2 = 1.23 wt%; Cr2O3 = 1.55 wt%. Pigeonite, Fs34.4-39.7Wo8.6-14.5 (FeO/MnO = 20), Al2O3 contents up to 3.2 wt %. Taenite Ni = 15.9-49.7, chromite cr# = 0.90, and FeS Ni = 1.58 wt %. Residuum glass (wt %): SiO2, 70; Al2O3, 13.8; Na2O, 9.4; K2O, 2.9; CaO 2.1; FeO, 2.8. Oxygen isotopes (D. Rumble, CIW): Replicate analyses of acid-washed whole rock samples by laser fluorination gave δ18O = 4.80, 4.73; δ17O = 3.72, 3.75; Δ17O =1.199,1.265 (all per mil).

Classification: Achondrite (ungrouped). Mineralogy and mineral chemistry are unlike those of any other known achondrite, and the oxygen isotopic composition plots well above the TFL in the field for LL chondrites.

Specimens: A total of 7.7 g of material including one polished thin section are on deposit at NAU. Mr. A. Habibi holds the main mass.

Data from:
  Table 0
  Line 0:
Place of purchase:Erfoud
Mass (g):38.4
Shock stage:low
Weathering grade:low
Ferrosilite (mol%):18.5-24.0
Wollastonite (mol%):36.7-41.2
Type spec mass (g):7.7
Type spec location:NAU
Main mass:A Habibi
Comments:Submitted by Bunch
Plots: O isotopes:  
   and collections
NAU: Geology, Bldg 12 Knoles Dr Northern Arizona University, Flagstaff, AZ 86011, United States; Website (institutional address; updated 12 Apr 2012)
UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012)
CIW: Carnegie Insitution Washington, Geophysical Laboratory, 5251 Broad Branch Rd., NW, Washington DC 20015, United States (institutional 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 1370 approved meteorites from Morocco (plus 16 unapproved names) (plus 1 impact crater)

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