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Northwest Africa 4222
Basic information Name: Northwest Africa 4222
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 4222
Observed fall: No
Year found: 2006
Country: (Northwest Africa)
Mass:help 16.5 g
Meteoritical Bulletin:  MB 94  (2008)  Martian (shergottite)
Recommended:  Martian (shergottite)    [explanation]

This is 1 of 324 approved meteorites (plus 2 unapproved names) classified as Martian (shergottite).   [show all]
Search for other: Martian meteorites
Comments: Approved 8 Sep 2008
Writeup from MB 94:

Northwest Africa 4222

Northwest Africa

Find: 2006

Martian (shergottite)

History: A small fragment was purchased in Erfoud by a Moroccan dealer for M. Chinellato.

Physical characteristics: The sample weighs 16.5 g and is partially covered with a black fusion crust.

Petrography: (V. Moggi Cecchi, G. Pratesi, MSP) Cumulitic fine-grained porphyritic texture consisting of few very large rounded and zoned phenocrysts of brown olivine up to 1350 μm in maximum size set in a fine-grained basaltic groundmass of twinned tabular pyroxene crystals from 80 to 240 μm wide and from 130 to 820 μm long surrounded by an interstitial glassy matrix. Pyroxene is primarily pigeonite with subordinate enstatite. Other minerals are chromite, titanian chromite and ilmenite, up to 100 μm in size, merrillite, and rare pyrrhotite grains up to 50 μm in size; shock features include strong mosaicism and planar deformation in olivine, undulose extinction and twinning in pyroxene.

Geochemistry and mineralogy: Olivine Fo58.9–68.7; orthopyroxene (core Fs17.2En80.3Wo2.4; rim Fs31.4En63.9Wo4.7, FeO/MnO = 30.2–42.4); pigeonite (core Fs24.1En65.5Wo10.3; rim Fs32.6En58.4Wo8.9), FeO/MnO = 32.5–46.5). Plagioclase (An61.1Or0.2). Oxygen isotopes (I. A. Franchi, R. Greenwood, OU): δ17O = 2.85‰, δ18O = 4.91‰, Δ17O = 0.30‰ (mean on 2 analyses).

Classification: Martian (shergottite). Low weathering and high shock.

Type specimens: A total of 3.55 g of sample and one thin section is on deposit at MSP. MChin holds the main mass.  

Data from:
  Table 2
  Line 7:
State/Prov/County:Northwest Africa
Mass (g):16.5
Fayalite (mol%):31.3-41.1
Ferrosilite (mol%):24.1-32.6
Wollastonite (mol%):8.9-10.3
Classifier:V. Moggi Cecchi, G. Pratesi, Museo di Scienze Planetarie
Type spec mass (g):3.5
Type spec location:MSP
Main mass:MChin
Comments:δ17O = 2.85‰, δ18O = 4.91‰, Δ17O = 0.30‰ (mean on 2 analyses)
Plots: O isotopes:  
   and collections
MSP: Museo di Scienze Planetarie, Via Galcianese 20/H, 59100 Prato, Italy, Italy; Website (institutional address; updated 22 Oct 2022)
OU: Planetary and Space Sciences Department of Physical Sciences The Open University Walton Hall Milton Keynes MK7 6AA United Kingdom, United Kingdom (institutional address; updated 8 Dec 2011)
MChin: Matteo Chinellato, Via Triestina, 126/A-30030 Tessera, Venezia, Italy; Website (private address)
References: Published in Meteoritical Bulletin, no. 94, MAPS 43, 1551-1588 (2008)
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Photos from the Encyclopedia of Meteorites:
Matteo Chinellato   

     This is 1 of 9776 approved meteorites from (Northwest Africa) (plus 1862 unapproved names)

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