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Northwest Africa 5312
Basic information Name: Northwest Africa 5312
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 5312
Observed fall: No
Year found: 2007
Country: (Northwest Africa)
Mass:help 354 g
Meteoritical Bulletin:  MB 95  (2009)  Diogenite
MB 103  (2014)  Mesosiderite
Recommended:  Mesosiderite    [explanation]

This is 1 of 269 approved meteorites classified as Mesosiderite.   [show all]
Search for other: Mesosiderites, Metal-rich meteorites
Comments: Approved 23 Dec 2008
Revised 11 Feb 2015: Revised classification
Writeup from MB 104:

Northwest Africa 5312, revised classification and description

History: Purchased by Fabien Kuntz in 2007 from a dealer in Rich, Morocco.

Physical characteristics: A 354 g dense stone (354 g) partially covered by moderately weathered fusion crust. The uncrusted surface has a dark brown coloration.

Petrography: (A. Irving, UWS and T. Bunch, NAU) Back-scattered electron imaging of a large polished endcut shows this specimen to be an aggregate of predominantly orthopyroxene and anorthite with accessory kamacite, taenite, silica polymorph, Mg-bearing merrillite, apatite and troilite. Some orthopyroxene grains are oikocrysts containing olivine chadacrysts. Sparse angular grains of olivine are present as well as sporadic breccia clasts. One such clast (13 mm by 11 mm) consists of angular olivine and orthopyroxene grains within a finer grained plagioclase-free, chromite and troilite-bearing matrix, and other breccia clasts (as large as 3.5 mm) are composed of orthopyroxene and olivine surrounded by fine-grained, polygonized orthopyroxene+olivine+apatite+chromite+troilite (or symplectic intergrowths of these minerals).

Geochemistry: (S. Kuehner, UWS and J. Wittke, NAU) Orthopyroxene (Fs20.6-25.1Wo1.5-2.6, FeO/MnO = 25-31, N = 3), olivine (Fa22.1-31.1, FeO/MnO = 42-48, N = 3), chromite (cr# = 0.73), taenite (Ni = 42.5 wt.%), merrillite (MgO = 3.6 wt.%). Oxygen isotopes (D. Rumble, CIW): acid-washed subsamples analyzed by laer fluorination gave, respectively, δ17O 1.545, 1.484; δ18O 3.364, 3.149, Δ17O -0.224, -0.173 (all per mil).

Classification: Mesosiderite.

Specimens: The entire 354 g stone including one polished thin section is at PSF.

Data from:
  Table 2
  Line 110:
Place of purchase:Rich
Mass (g):354
Fayalite (mol%):22.1
Ferrosilite (mol%):20.6
Wollastonite (mol%):1.5
Classifier:T. Bunch and J. Wittke, NAU
Type spec mass (g):21.17
Type spec location:PSF
Main mass:location not given
Comments:?17O, 1.545 and 1.484; ?18O, 3.364 and 3.149
Plots: O isotopes:  
   and collections
NAU: Geology, Bldg 12 Knoles Dr Northern Arizona University, Flagstaff, AZ 86011, United States; Website (institutional address; updated 12 Apr 2012)
PSF: Planetary Studies Foundation,10 Winterwood Lane, Unit B, Galena, Illinois 61036-9283, United States; Website (institutional address; updated 1 Dec 2011)
UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012)
CIW: Carnegie Insitution Washington, Geophysical Laboratory, 5251 Broad Branch Rd., NW, Washington DC 20015, United States (institutional address)
Kuntz: Fabien Kuntz, France; Website (private address)
References: Published in Meteoritical Bulletin, no. 95, MAPS 44, 429-462 (2009)
Published in Meteoritical Bulletin, no. 104, MAPS 52, 2284, Octover 2017, http://onlinelibrary.wiley.com/doi/10.1111/maps.12930/full
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     This is 1 of 9570 approved meteorites from (Northwest Africa) (plus 1871 unapproved names)

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