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Northwest Africa 16331
Basic information Name: Northwest Africa 16331
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 16331
Observed fall: No
Year found: 2021
Country: (Northwest Africa)
Mass:help 7.93 kg
Meteoritical Bulletin:  MB 112  (2024)  LL3.3
Recommended:  LL3.3    [explanation]

This is 1 of 16 approved meteorites classified as LL3.3.   [show all]
Search for other: LL chondrites, LL chondrites (type 3), Ordinary chondrites, and Ordinary chondrites (type 3)
Comments: Approved 3 Jan 2024
Writeup from MB 112:

Northwest Africa 16331 (NWA 16331)

(Northwest Africa)

Purchased: 2021

Classification: Ordinary chondrite (LL3.3)

History: Cascadia received a 32.7 g slice from Craig Zlimen/Minnesota Meteorites. In 2021, Mr. Zlimen purchased the single 7.93 kg stone from an Algerian dealer who said that it was found in Algeria in 2018

Physical characteristics: Physical Characteristics: The edges of the slice received by Cascadia is entirely surrounded by a weathered broken surface; a small patch (1.5 × 1.0 cm area) of black fusion crust remains on one edge. The cut faces of the slice display numerous chondrules, many rimmed by sulfide. Although not an obvious breccia, three roughly rectangular large clasts with a crystalline texture were visible on the cut faces. One side of the slice is notably browner in color and cross-cut by weathering veins. The thin section was prepared from the less weathered side of the slice, and included part of one of the large clasts.

Petrography: (M. Hutson, A. Ruzicka, Cascadia): In thin section, the sample is comprised of numerous chondrules and chondrule fragments set in a fragmental matrix. Many chondrules have glassy mesostases; some mesostases are just glass, whereas other glassy mesostases contain crystallites. Most chondrules are ovoid and roughly aligned, and are variable in size, but with many (N=20) ? 1 mm in length. Roughly 40% of the chondrules have partial to complete sulfide-rich rims. One large (~3 × 2.5 mm exposed area) roughly rectangular clast is truncated by the edge of the section. The clast is comprised of olivine phenocrysts (up to 250 µm across) and smaller (up to about 70 microns long) pyroxene grains, consisting of low-Ca cores with high-Ca rims, set in a mesostasis comprised of crystallite-filled glass. There is about 20-25% replacement of metal and troilite in the section. Troilite is abundant (~5-8 area%), primarily forming rims around chondrules, but also occurring as troilite-rich clumps between chondrules. Metal occurs as rare (~1-2 area%) small grains both in chondrule rims and in troilite-rich clumps.

Geochemistry: Olivine is highly unequilibrated (Fa23.6±14.4, range Fa2.8-56.9, coefficient of variation of Fa = 60.9, Cr2O3=0.1±0.1, N=55); clast olivine (Fa10.7±4.2, N=7). Low-calcium pyroxene (Fs12.1±6.8Wo1.2±1.1, range Fs4.4-25.9Wo0.2-3.9, N=18); clast low-calcium pyroxene (Fs12.4±1.2Wo1.1±0.8, N=4).

Classification: Ordinary chondrite (LL3.3), with LL-group indicated by low metal abundance, and the presence of numerous large chondrules. Cr2O3 in olivine is consistent with subtype ?3.2. Coefficient of variation of Fa in olivine suggests subtype 3.0-3.4 (Sears and Dodd, 1988), while pyroxene Fs vs. ?Fs suggests subtype 3.0-3.3. Chemistry along with high glass contents in chondrule mesostases are consistent with a subtype of 3.3

Specimens: Cascadia holds 27.6 g in one piece, as well as a polished thin section and material in an epoxy butt; Craig Zlimen/Minnesota Meteorites holds the main mass.

Data from:
  Table 0
  Line 0:
Place of purchase:online
Date:P 2021
Mass (g):7930
Shock stage:S4
Weathering grade:W2
Fayalite (mol%):23.6±14.4 (N=55)
Ferrosilite (mol%):12.1±6.8 (N=18)
Wollastonite (mol%):1.2±1.1 (N=18)
Classifier:M. Hutson and A. Ruzicka, Cascadia
Type spec mass (g):32.7
Type spec location:Cascadia
Main mass:Craig Zlimen/Minnesota Meteorites
Comments:Lab number CML 1656, Craig Zlimen number ZLI 083; submitted by Melinda Hutson
   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 Gattacceca J., McCubbin F. M., Grossman J. N., Schrader D. L., Cartier C., Consolmagno G., Goodrich C., Greshake A., Gross J., Joy K. H., Miao B. and Zhang B. (2024) The Meteoritical Bulletin, no. 112. Meteoritics & Planetary Science 59, 1820–1823. ?
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Public domain photographs:
Melinda Hutson      

     This is 1 of 9829 approved meteorites from (Northwest Africa) (plus 1851 unapproved names)

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