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Northwest Africa 13312
Basic information Name: Northwest Africa 13312
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 13312
Observed fall: No
Year found: 2019
Country: (Northwest Africa)
Mass:help 45 g
Recommended:  Achondrite-ung    [explanation]

This is 1 of 119 approved meteorites classified as Achondrite-ung.   [show all]
Search for other: Achondrites, Ungrouped achondrites
Comments: Approved 13 Jun 2020
Writeup from MB 109:

Northwest Africa 13312 (NWA 13312)

(Northwest Africa)

Purchased: 2019 Sep

Classification: Ungrouped achondrite

History: Purchased by Mbark Arjdal in September 2019 from a dealer in Timbuktu, Mali.

Petrography: (A. Irving, UWS and P. Carpenter, WUSL) Fresh specimen with a complex igneous poikilitic texture and variable grainsize composed predominantly of coarser grained zoned pyroxene oikocrysts (0.5-2 mm) enclosing subordinate olivine chadacrysts (0.1-0.3 mm), plus finer grained interstitial regions. Accessory phases are chromite, troilite, and very rare small grains of taenite and slightly stained kamacite; no phosphates were observed. Pyroxenes are zoned from orthopyroxene cores (exhibiting prominent polysynthetic twinning) to more ferroan pigeonite and subcalcic augite rims. Sporadic very large homogeneous macrocrysts (up to 0.6 cm across) of both olivine and orthopyroxene are also present. Interstitial regions consist of subparallel intergrowths of acicular calcic plagioclase, high-Ca pyroxene and silica polymorph accompanied by minor ilmenite, Ni-bearing pyrrhotite and pentlandite.

Geochemistry: Olivine (Fa20.4-35.1, FeO/MnO = 47-51, N = 10), orthopyroxene cores (Fs11.8-14.2Wo0.2-0.3, FeO/MnO = 31-34, N = 4), low-Ca pyroxene rims (Fs23.7-35.2Wo2.0-4.9, FeO/MnO = 28-32, N = 6), subcalcic augite (Fs32.0-40.8Wo33.7-24.0, FeO/MnO = 25-27, N = 5), pigeonite (Fs29.4Wo14.7; Fs45.1-47.0Wo7.1-9.7; FeO/MnO = 26-30; N = 3), plagioclase (An68.2-86.4Or2.3-0.7, N = 3). Magnetic susceptibility log χ (× 10-9 m3/kg) = 3.07.

Classification: Achondrite (ungrouped, igneous, poikilitic, metal-poor).

Specimens: 9.7 g including one polished thin section at UWB; remainder with Mr. M. Arjdal.

Data from:
  Table 0
  Line 0:
Place of purchase:Timbuktu, Mali
Date:P 2019 Sep
Mass (g):45
Shock stage:low
Weathering grade:low
Fayalite (mol%):20.4-35.1
Ferrosilite (mol%):11.8-14.2; 23.7-35.2; 32.0-40.8
Wollastonite (mol%):0.2-0.3; 2.0-4.9; 33.7-20.3
Classifier:A. Irving, UWS, and P. Carpenter, WUSL
Type spec mass (g):9.7
Type spec location:UWB
Main mass:M. Arjdal
Comments:Work name Arj ZM 205; submitted by A. Irving
   and collections
UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012)
WUSL: Washington Univ., One Brookings Drive, St. Louis, MO 63130, United States (institutional address; updated 17 Oct 2011)
UWB: University of Washington, Box 353010 Seattle, WA 98195, United States (institutional address; updated 27 Jul 2012)
References: Published in Meteoritical Bulletin, no. 109, in preparation (2020)
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     This is 1 of 8674 approved meteorites from (Northwest Africa) (plus 1882 unapproved names)

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