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Northwest Africa 11915
Basic information Name: Northwest Africa 11915
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 11915
Observed fall: No
Year found: 2013
Country: (Northwest Africa)
Mass:help 718 g
Meteoritical Bulletin:  MB 107  (2018)  LL4-6
Recommended:  LL4-6    [explanation]

This is 1 of 91 approved meteorites classified as LL4-6.   [show all]
Search for other: LL chondrites, LL chondrites (type 4-7), Ordinary chondrites, and Ordinary chondrites (type 4-7)
Comments: Approved 24 Jul 2018
Writeup from MB 107:

Northwest Africa 11915 (NWA 11915)

(Northwest Africa)

Purchased: 2013

Classification: Ordinary chondrite (LL4-6)

History: Purchased by John A. Shea in 2013 via E-bay from Mirko Graul who acquired it in a lot of northwest African meteorites.

Physical characteristics: Exterior surface covered by reddish brown weathering patina and patches of black fusion crust. Cut faces show angular dark bluish-gray clasts amid a beige host lithology, along with a few metal and sulfide grains and patches of rust.

Petrography: Three lithologies are readily distinguished in thin section. A lighter colored coarse-grain clast (clast B), approximately 400 × 600 μm, with a highly integrated texture is encompassed within a larger clast (clast A) which has a well integrated texture with barely distinguishable chondrules. Clast A is truncated along the edge of the section, but is approximately 1.2 cm long. The two clasts are set in a host which has readily delineated chondrules, smaller clasts, and fragments. Approximately 85% of the opaque grains have been replaced by Fe-hydroxide weathering product. In BSE imaging, host olivine grains appear equilibrated, but many larger host pyroxene grains are zoned. The host is brecciated on a fine scale: a single large (150 micron long) plagioclase feldspar grain, is located adjacent to a chondrule fragment with strongly-zoned low-calcium pyroxene grains with a mesostasis of devitrified glass. A rectangular clast (approximately 1.1 × 0.8 mm) consists of zoned low-calcium clinopyroxene enclosing a large patch of mostly replaced troilite containing silica polymorph rimmed by high-Ca pyroxene. Chondrules, clasts and larger mineral grains in the host are surrounded by a finer-grained (typically 5-20 μm across grains) of olivine, low-calcium pyroxene, and plagioclase feldspar grains.

Geochemistry: (M. Hutson and A. Ruzicka, Cascadia) Both host olivine (Fa30.2±0.4, N=17) and clast B olivine (Fa 30.3 ± 0.1) are equilibrated. Clast B low-Ca pyroxene (Fs25.6±0.3Wo2.0±0.2, N=9) is also equilibrated; however host low-Ca pyroxene (Fs19.9±4.0Wo1.0±0.8, N=28) is variable. Clast B plagioclase feldspar is albitic (Ab84.5±1.1An11.3±0.6Or4.2±0.5, N=3).

Classification: LL4-6 based on chemistry and texture.

Specimens: Cascadia holds 83.5 g in two pieces, in addition to one polished thin section and a mounted butt

Data from:
  Table 0
  Line 0:
Place of purchase:E-bay
Date:P 2013
Mass (g):718.0
Shock stage:S2
Weathering grade:W3
Fayalite (mol%):30.2±0.4, 30.3±0.1
Ferrosilite (mol%):19.9±4.9, 25.6±0.3
Wollastonite (mol%):1.0±0.8, 2.0±0.2
Classifier:M. Hutson and A. Ruzicka, Cascadia
Type spec mass (g):83.5
Type spec location:Cascadia
Main mass:John A. Shea, 8723 Maplebrook Parkway N., Brooklyn Park, MN 55445
Comments:Lab number CML0817; submitted by A. Ruzicka
   and collections
Cascadia: Cascadia Meteorite Laboratory, Portland State University, Department of Geology, Room 17 Cramer Hall, 1721 SW Broadway, Portland, OR 97201, United States; Website (institutional address; updated 28 Oct 2011)
References: Published in Meteoritical Bulletin, no. 107, MAPS 55, 460-462
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     This is 1 of 9806 approved meteorites from (Northwest Africa) (plus 1855 unapproved names)

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