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Northwest Africa 16533
Basic information Name: Northwest Africa 16533
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 16533
Observed fall: No
Year found: 2022
Country: (Northwest Africa)
Mass:help 300 g
Classification
  history:
Recommended:  Howardite-an    [explanation]

This is 1 of 2 approved meteorites classified as Howardite-an.   [show all]
Search for other: Achondrites, HED achondrites, and Howardites
Comments: Approved 30 Mar 2024
Writeuphelp
Writeup from MB 113:

Northwest Africa 16533 (NWA 16533)

(Northwest Africa)

Purchased: April 2022

Classification: HED achondrite (Howardite, anomalous)

History: Purchased in April 2022 by Tim Stout from a meteorite dealer in Tindouf Algeria.

Physical characteristics: Single stone with a moderately weathered dark brown fusion crust.

Petrography: (D. Sheikh, Cascadia) Specimen represents a polymict breccia composed of a mix of lithic and monomineralic clasts/clast fragments (most sub-mm, largest ~4 mm) set within a fine-grained fragmental matrix. Diogenitic and eucritic (primarily basaltic clasts with few cumulate clasts) components comprise ~80 vol. % and ~20 vol. % of the clast inventory, respectively. Pyroxenes in the eucritic portion typically display thin, sub-μm-sized bands of exsolution lamellae. Anomalous monomineralic Mg-rich olivine and low-Ca pyroxene clasts are present in the diogenitic portion of this sample. Accessory phases identified in the sample include chromite, silica polymorph, and troilite.

Geochemistry: Diogenitic Component [Regular Olivine (Fa28.7±2.6, range Fa25.7-30.6, Fe/Mn=45±5, n=3), Mg-rich Olivine (Fa12.2±0.9, range Fa10.4-12.9, Fe/Mn=38±4, n=11), Regular Low-Ca Pyroxene (Fs25.3±3.3Wo2.0±0.6, range Fs21.5-36.2Wo1.1-3.5, Fe/Mn=28±2, n=22), Mg-rich Low-Ca Pyroxene (Fs15.6±2.1Wo1.3±0.7, range Fs12.6-17.5Wo0.6-2.1, Fe/Mn=31±3, n=4)]; Eucritic Component [Low-Ca Pyroxene (Fs59.0±7.1Wo2.9±1.2, range Fs41.3-63.9Wo1.4-4.6, Fe/Mn=30±2, n=16), Pigeonite (Fs56.6±6.5Wo8.4±3.2, range Fs43.8-62.9Wo5.4-12.8, Fe/Mn=30±1, n=7), High-Ca Pyroxene (Fs32.7±6.9Wo37.1±5.7, range Fs15.8-44.9Wo25.6-44.7, Fe/Mn=31±3, n=15), Calcic Plagioclase (An82.9±4.9, range An75.2-93.3, n=17)].

Classification: Howardite (anomalous) due to the presence of unusual, Mg-rich monomineralic olivine and pyroxene mineral fragments that are compositionally similar to Mg-rich olvine and Low-Ca pyroxene mineral clasts from howardites reported in Lunning et al. 2015, Mg-rich harzburgites reported in Hahn et al. (2018) and Mg-rich olivines and low-Ca pyroxenes reported in anomalous diogenite Djebel Chaab 004.

Specimens: 23.7 g at Cascadia, main mass with Tim Stout.

Bibliography:
  • Hahn T. M., Lunning N. G., McSween H. Y., Bodnar R. J. and Taylor L. A. (2018) Mg?rich harzburgites from Vesta: Mantle residua or cumulates from planetary differentiation? Meteoritics & Planetary Science 53, 514–546. (link)
Data from:
  MB113
  Table 0
  Line 0:
Place of purchase:Algeria
Date:P April 2022
Mass (g):300
Pieces:1
Class:Howardite-an
Shock stage:moderate
Weathering grade:moderate
Fayalite (mol%):28.7±2.6, 12.2±0.9
Ferrosilite (mol%):25.3±3.3, 15.6±2.1, 59.0±7.1, 56.6±6.5, 32.7±
Wollastonite (mol%):2.0±0.6, 1.3±0.7, 2.9±1.2, 8.4±3.2, 37.1±5.7
Classifier:D. Sheikh, Cascadia
Type spec mass (g):23.7
Type spec location:Cascadia
Main mass:Tim Stout
Comments:CML 1538; submitted by Daniel Sheikh
Institutions
   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)
Catalogs:
References: Published in Meteoritical Bulletin, no. 113, in preparation (2024)
Find references in NASA ADS:
Find references in Google Scholar:
Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 9699 approved meteorites from (Northwest Africa) (plus 1854 unapproved names)

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