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Northwest Africa 5721
Basic information Name: Northwest Africa 5721
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 5721
Observed fall: No
Year found: 2007
Country: Western Sahara
Mass:help 67.5 g
Meteoritical Bulletin:  MB 99  (2011)  Eucrite
Recommended:  Eucrite    [explanation]

This is 1 of 605 approved meteorites (plus 1 unapproved name) classified as Eucrite.   [show all]
Search for other: Achondrites, Eucrites, and HED achondrites
Comments: Approved 4 Jan 2011
Writeup from MB 99:

Northwest Africa 5721 (NWA 5721)


Found: 2007

Classification: HED achondrite (Eucrite)

History: A small dark stone was found in SW Morocco (Western Sahara) in 2007 and purchased in Erfoud by an anonymous buyer.

Physical characteristics: A single fresh stone (67.5 g) with a dark gray, partly translucent fusion crust, and containing numerous millimeter-sized vesicles of pre-terrestrial origin.

Petrography: (T. Bunch and J. Wittke, NAU; A. Irving, UWS): The texture is dominated by long (<12 mm), bladed, dark pyroxenes; some swallow-tailed shapes are present and form lamellar textures with plagioclase, in addition to ophitic to sub ophitic textures. Smaller sub-textures include variolitic and plumose with interstitial poikilitic residuum that contains tiny pyroxenes set in masses of a low birefringent silica phase, iron sulfide (probably troilite), fayalite, metal, ilmenite, and felsic glasses. Pigeonite and augite textures are complex, with large changes in grainsize over short distances. Numerous irregularly-shaped, smooth-walled, empty vesicles range in size from 0.2 to 2.5 mm.

Geochemistry: Pigeonite (Fs53.2-68.1Wo13.5-8.0, FeO/MnO = 35), augite (Fs39.4-44.4Wo32.2-36.7, FeO/MnO = 27), olivine (Fa85.7, FeO/MnO = 48), plagioclase (An82.3-88.0). Oxygen isotopes (D. Rumble, CIW): acid-washed material analyzed in replicate by laser fluorination gave, respectively, δ18O = 2.93, 2.99; δ17O = 1.26, 1.32; Δ17O = -0.281, -0.254 per mil. This composition plots at the lower bound of the field for eucrites. Bulk composition (by ICP-AES and ICPMS, J.-A. Barrat, UBrest): in wt. %, TiO2 0.58, Al2O3 12.49, FeO 19.62, MnO 0.55, MgO 4.07, CaO 10.46, Na2O 0.43, P2O5 0.21; in ppm, La 1.64, Ce 4.24, Nd 3.21, Sm 1.05, Eu 0.47, Gd 1.47, Yb 1.30, Lu 0.20, Rb 0.7, Sr 68, Ba 20, Ni 1.2, Ga 2.8. The chondrite-normalized REE pattern is essentially flat at ~5.4x chondrites, with a small positive Eu anomaly.

Classification: Achondrite (eucrite). Although this specimen has mineral compositions and oxygen isotopic composition similar to those of typical eucrites, it differs from them in the following significant ways: presence of abundant vesicles, low bulk MgO content and very high FeO/MgO ratio (both beyond values for basaltic eucrites, and reflected in the high ferrosilite contents of some constituent pyroxenes), high Ga/Al ratio (~1.75 times higher than in eucrites), rare earth element abundances ~1.65 times lower than those in basaltic eucrites, and much higher abundances of P and Rb than in eucrites. Shock level and weathering grade are both low.

Specimens: 13.8 g and one polished thin section are on deposit at NAU. The main mass is held by an anonymous owner.

Data from:
  Table 0
  Line 0:
Place of purchase:Erfoud
Mass (g):67.5
Shock stage:low
Weathering grade:very low
Fayalite (mol%):85.7
Ferrosilite (mol%):53.2-68.1; 39.4-44.4
Wollastonite (mol%):13.5-8.0; 32.2-36.7
Classifier:T. Bunch, J. Wittke, A. Irving
Type spec mass (g):13.8
Type spec location:NAU*
Main mass:Anon
Comments:Submitted by T. Bunch
Plots: O isotopes:  
   and collections
NAU*: Collection discontinued. Specimens redistributed as shown in individual meteorite records, United States (institutional address; updated 24 Jun 2024)
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)
UBrest: Université de Bretagne Occidentale 3 Rue des Archives, 29238 Brest, France (institutional address; updated 2 Nov 2016)
NAU: Geology, Bldg 12 Knoles Dr Northern Arizona University, Flagstaff, AZ 86011, United States (institutional address; updated 12 Apr 2012)
References: Published in Meteoritical Bulletin, No. 99, April 2012, MAPS 47, E1-E52 (2012) [published online only]
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Western Sahara

     This is 1 of 281 approved meteorites from Western Sahara (plus 20 unapproved names)

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