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Northwest Africa 10928
Basic information Name: Northwest Africa 10928
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 10928
Observed fall: No
Year found: 2015
Country: (Northwest Africa)
Mass:help 148 g
Classification
  history:
Meteoritical Bulletin:  MB 105  (2016)  Eucrite-pmict
Recommended:  Eucrite-pmict    [explanation]

This is 1 of 344 approved meteorites classified as Eucrite-pmict.   [show all]
Search for other: Achondrites, Eucrites, and HED achondrites
Comments: Approved 3 Dec 2016
Writeuphelp
Writeup from MB 105:

Northwest Africa 10928 (NWA 10928)

(Northwest Africa)

Purchased: 2015

Classification: HED achondrite (Eucrite, polymict)

History: On 2015, meteorite specimens were purchased by José Antonio Sanchez Santana in the Saharawi refugee camps in Tindouf, Algeria.

Physical characteristics: Eighty-eight brownish to dark gray stones weighing 148 g in total were found in the desert. Each individual specimen weights between 0.5 and 10 g. Irregular exterior, no fusion crust. A saw cut reveals a polymict breccia with numerous fragmental light and dark clasts.

Petrography: Petrographic description (J. Llorca, UPC). The meteorite is a microbreccia of clasts in a semi-opaque dark brown microcrystalline impact melt matrix. The matrix is heterogeneous and is composed of mono and polymineralic fragments. Clast/matrix ratio is approximately 85/15. The larger clasts (maximum dimension 5 mm) are mainly of pyroxenitic, anorthositic and basaltic lithologies; many have been shocked and partly granulated. The smaller clasts (minimum dimension less than 0.1 mm) are individual mineral grains (mainly pyroxene and plagioclase). The most abundant minerals are low-Ca pyroxene, all white thick pigeonite exsolution lamellae, and anorthite. Olivine is scarce and occurs in small amounts as fine grains. Accessory minerals are ilmenite and Al-Ti-bearing chromite.

Geochemistry: Mineral compositions (Rafael Pablo Lozano, IGME). Microprobe analyses show plagioclase ranges from An92-95 with a mean of An94.1±1.2 (n=9). Pyroxene is variable in composition: low-Ca pyroxene (Fs42-69Wo2-4; Fe/Mn=26-36) with a mean of Fs58.2±8.4 (10), contain pigeonite exsolution lamellae (Fs23-36Wo29-44; Fe/Mn=28-38) with a mean of Fs29.9±4.0 (n=11). Low-Ca pyroxene and pigeonite grains have Fe/(Fe+Mg)=0.607–0.846 with Ti/(Ti+Cr)=0.52–0.99. Olivine: Fo14-27 (mean: Fo21.6±4.5; n=11) has Fe/Mn=39-49 and chromite has Cr/(Cr+Al)=0.87. Bulk chemistry (J. Reyes, IGME). One gram of sample for the analysis. XRF of two specimens gave average abundances of (in wt.%): SiO2=46.46, TiO2=0.67, Al2O3=12.10, Fe2O3=20.45, MgO=6,09, CaO=11.39 and K2O<0.25. Na2O= 0.42 wt.% by AAS. Trace elements were measured with ICP-MS (all in ppm): Be=0.24, V=54.4, Cr=1369, Co=4.71, Ni=2.23, Cu=2.49, Zn=5.06, As=0.84, Se=3.10, Mo<0.5, Ag<0.1, Cd=2.61, Sb=0.38, Ba=1645, Tl<0.1, Pb=2.89, Th=0.30 and U=0.18.

Classification (R. P. Lozano, IGME). Achondrite, polymict eucrite. Terrestrial weathering is moderate with carbonate veins.

Specimens. Twelve specimens (25.4 g in total) and two probe mounts are on deposit at Museo Geominero (IGME). A thin section is on deposit at UPC. José Antonio Sánchez Santana holds the main mass.

Data from:
  MB105
  Table 0
  Line 0:
Place of purchase:Saharawi refugee camps, Tindouf, Algeria
Date:P 2015
Mass (g):148
Pieces:88
Class:Eucrite-pmict
Weathering grade:moderate
Ferrosilite (mol%):58.2±8.4 (N=10); 29.9±4.0 (N=11)
Wollastonite (mol%):5.7±5.8; 40.7±4.0
Classifier:R.P. Lozano, IGME
Type spec mass (g):35.4
Type spec location:IGME
Main mass:José Antonio Sánchez Santana
Comments:Submitted by Rafael Pablo Lozano Fernández
Institutions
   and collections
UPC: Institut de Tècniques Energètiques, Universitat Politècnica de Catalunya Diagonal 647, ed. ETSEIB, 08028 Barcelona, Spain, Spain (institutional address; updated 3 May 2015)
IGME: Museo Geominero, Instituto Geológico y Minero de España, Ríos Rosas 23, 28003 Madrid, Spain (institutional address; updated 12 Dec 2012)
Catalogs:
References: Published in Meteoritical Bulletin, no. 105, MAPS 52, 2411, September 2017. http://onlinelibrary.wiley.com/doi/10.1111/maps.12944/full
Find references in NASA ADS:
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Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 7101 approved meteorites from (Northwest Africa) (plus 2004 unapproved names)

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