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Northwest Africa 11998
Basic information Name: Northwest Africa 11998
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 11998
Observed fall: No
Year found: 2017
Country: (Northwest Africa)
Mass:help 2.24 kg
Meteoritical Bulletin:  MB 107  (2018)  Eucrite
Recommended:  Eucrite    [explanation]

This is 1 of 576 approved meteorites (plus 1 unapproved name) classified as Eucrite.   [show all]
Search for other: Achondrites, Eucrites, and HED achondrites
Comments: Approved 27 Sep 2018
Writeup from MB 107:

Northwest Africa 11998 (NWA 11998)

Northwest Africa

Purchased: 2017

Classification: HED achondrite (Eucrite)

History: A 2241 g, partially fusion-crusted stone was found near Laayoune, Western Sahara, in 2016. J. Donald Cline and John Sinclair Purchased the stone from Mohamed Ismaily at the Tucson Gem and Mineral show in 2017.

Physical characteristics: Sample is dark blackish brown in color, non-magnetic and has an irregular shape. Clasts are readily visible on the exterior of the sample. Clasts range in size from 0.25-2 cm, are light colored, rounded to angular in shape and have very-fine to coarse grained igneous textures.

Petrography: Description and classification (A. Love, App): Sample is a breccia composed of clasts of basaltic-cumulate lithologies contained by a host of similar clastic debris set within a micro-vesicular melted matrix. Clasts are: fine-grained recrystallized basalt (25-50 µm phenocrysts); gabbroic clast with 423-512 µm pyroxenes and 348-506 µm plagioclase and rare (<1vol%) diogenite. All pyroxenes are exsolved. Some clasts show breccia in breccia structure. Additional minerals and phases are: ilmenite, chromite, FeS, apatite, rare olivine and rare FeNi metal.

Geochemistry: (A. Love, App) Basaltic eucrite: Low-Ca pyroxene host Fs43.9±2.2Wo1.7±0.1 (Fs40.7-46.4Wo1.5-1.8, FeO/MnO=33.2-37.4), N=8; high-Ca pyroxene exsolution lamellae Fs17.5±0.4Wo44.6±0.4 (Fs17.0-17.8Wo44.1-44.8), N=3. Cumulate eucrite: Low-Ca pyroxene host Fs61.7±2.7Wo2.1±0.3 (Fs54.1-64.3Wo1.7-2.6, FeO/MnO=30.5-34.7 N=11); high-Ca pyroxene exsolution lamellae Fs27.3±1.1Wo43.0±0.6 (Fs26.1-29.0Wo42.2-44.1, N=6); plagioclase An87.2±3.2Or0.5±0.6 (An80.3-90.9Or0.0-2.3 N=10). Diogenite: Low-Ca pyroxene Fs23.5Wo2.6 (FeO/MnO=30.15, N=1); Olivine Fa54.3±1.1, N=2.

Classification: HED (polymict eucrite breccia). FeO/MnO and Fs compositions of pyroxenes indicate this sample is a HED meteorite. Textural and compositional data indicate this is a polymict eucrite melt breccia.

Specimens: PARI holds the main mass. One slice totaling 35.6 g and a polished thin section are on deposit at App.

Data from:
  Table 0
  Line 0:
Place of purchase:Tucson Gem and Mineral Show
Date:P 2017
Mass (g):2241
Shock stage:moderate
Weathering grade:low
Ferrosilite (mol%):43.9±2.2; 61.7±2.7; 17.5±0.4; 27.3±1.1; 23.5
Wollastonite (mol%):1.7±0.6; 44.6±0.4; 2.1±0.3; 43.0±0.6; 2.5
Classifier:A. Love, App
Type spec mass (g):35.6
Type spec location:App
Main mass:PARI
Comments:Submitted by Anthony Love
   and collections
App: Department of Geology, 572 Rivers St., Appalachian State University, Boone, NC 28608, United States (institutional address; updated 7 Mar 2013)
PARI: Pisgah Astronomical Research Institute 1 Pari Dr Rosman, NC 28772, United States (institutional address; updated 13 Sep 2016)
References: Published in Meteoritical Bulletin, no. 107, MAPS 55, 460-462
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     This is 1 of 9116 approved meteorites from (Northwest Africa) (plus 1873 unapproved names)

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