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Northwest Africa 12860
Basic information Name: Northwest Africa 12860
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 12860
Observed fall: No
Year found: 2019
Country: (Northwest Africa)
Mass:help 321 g
Meteoritical Bulletin:  MB 108  (2020)  Mesosiderite
Recommended:  Mesosiderite    [explanation]

This is 1 of 221 approved meteorites classified as Mesosiderite.   [show all]
Search for other: Mesosiderites, Metal-rich meteorites
Comments: Approved 21 Sep 2019
Writeup from MB 108:

Northwest Africa 12860 (NWA 12860)

(Northwest Africa)

Purchased: 2019

Classification: Mesosiderite

History: Eleven stones weighing 321 g were found in Western Sahara prior to 2019. John Sinclair and J. Donald Cline purchased the samples from a meteorite dealer while at the 2019 Tucson Gem and Mineral Show.

Physical characteristics: Eleven fragments, some of which fit together, comprise a single flight-oriented stone. The largest fragment has a black fusion crust coating 70% of its surface area, shows rollover lipping, and has an irregular pyramidal shape. The interior shows an obvious brecciated texture with coarse clasts up to 1 cm.

Petrography: Description and classification (A. Love, App): Sample is a breccia composed of 26 vol% FeNi metal, ~58 vol% Opx (up to 1 cm), 4 vol% plagioclase and 1 vol% olivine. Opx and plag comprise 93 vol% and 6 vol% of the silicates respectively. Pyroxenes poikolitically enclose olivine. Recrystallization is present in fine-grained regions and within some of the clasts. Average grainsize in fine-grained regions is 51µm. Additional minerals are apatite, troilite, kamacite, taenite and chromite.

Geochemistry: (A. Love, App) Olivine (Fa23.8±1.0 (Fa23.0-25.7), Fe/Mn=41.7±1.9, N=5), low Ca pyroxene Fs23.4±0.8Wo2.0±0.3 (Fs22.0-24.4Wo1.7-2.8), Fe/Mn=27.0±0.5, N=14), plagioclase An93.4±1.5Or0.2±0.1 (An90.9-95.6Or0.1-0.4, N=10).

Classification: Mesosiderite (estimated class C3). Mesosiderite based on texture, modal abundance of metal and magnetic susceptibility. Class C based on modal abundance of plagioclase (6 vol%) and orthopyroxene (93 vol%) of one thin section. Metamorphic grade 3 based on recrystallized nature of fine-grained regions.

Specimens: PARI holds the main masses. A polished thin section and a 20.98 g fragment are on deposit at App.

Data from:
  Table 0
  Line 0:
Place of purchase:Tucson Gem and Mineral Show
Date:P 2019
Mass (g):321
Shock stage:low
Weathering grade:low
Fayalite (mol%):23.8±1.0
Ferrosilite (mol%):23.4±0.8
Wollastonite (mol%):2.0±0.3
Magnetic suscept.:5.40
Classifier:A. Love, App
Type spec mass (g):20.98
Type spec location:App
Main mass:PARI
Comments:Submitted by Anthony Love
   and collections
App: Department of Geology, 572 Rivers St., Appalachian State University, Boone, NC 28608, United States (institutional address; updated 7 Mar 2013)
PARI: Pisgah Astronomical Research Institute 1 Pari Dr Rosman, NC 28772, United States (institutional address; updated 13 Sep 2016)
References: Published in Meteoritical Bulletin, no. 108 (2020) Meteorit. Planet. Sci. 55, 1146-1150
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     This is 1 of 8025 approved meteorites from (Northwest Africa) (plus 1951 unapproved names)

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