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Northwest Africa 13857
Basic information Name: Northwest Africa 13857
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 13857
Observed fall: No
Year found: 2020
Country: Algeria
Mass:help 476 g
Classification
  history:
Recommended:  Achondrite-ung    [explanation]

This is 1 of 124 approved meteorites classified as Achondrite-ung.   [show all]
Search for other: Achondrites, Ungrouped achondrites
Comments: Approved 6 May 2021
Writeuphelp
Writeup from MB 110:

Northwest Africa 13857 (NWA 13857)

Algeria

Purchased: 2020

Classification: Achondrite (ungrouped)

History: Fabien Kuntz purchased the 475.9 g sample from a meteorite prospector in Tindouf, Algeria, in 2020.

Physical characteristics: The exterior is dark-brownish orange and irregular shaped. The interior is weathered, dark-brown and has a crystalline texture.

Petrography: Description and classification (A. Love, App) Sample shows poikilitic texture composed of (vol%): 2mm (n=15) orthorhombic pyroxene oikocrysts (31), 114µm (n=46), yellow to brown stained, subhedral-euhedral olivine (52) occurring as chadacrysts and phenocrysts. Some pyroxenes are lath-shaped have rims of Ca-rich pyroxene. These phases are set within a vesicular, high-Si (~70wt% SiO2) glass containing rounded FeS and euhedral chromite. Chondrules are absent. Additional minerals are: rounded blebs of troilite, chromite, apatite, FeOH. Sample vestiges or relict chondritic-textured lithologies; evidence of rapid growth textures (cellular metal-sulfide mixtures, or spherical metal droplets).

Geochemistry: Olivine (Fa25.9±1.5, Fe/Mn=45.1±1.7, n=14); low-Ca Pyroxene (Fs18.2±0.9Wo2.3±1.1, Fe/Mn=29.7±1.7, n=5); high-Ca pyroxene (Fs15.0±1.2Wo30.7±2.9, Fe/Mn=23.3±2.8, n=7); glass (wt%: Na2O=3.6; Al2O3=19.6; SiO2=71.0; K2O=0.92; CaO=3.3; FeO=1.4). Oxygen Isotopes: (K. Ziegler, UNM) analyses of acid-washed subsamples by laser fluorination gave (all per mill): δ17O=3.917, 3.730; δ18O=5.590, 5.095; Δ17O=0.966, 1.040.

Classification: Achondrite (ungrouped) strong shock, moderate weathering. Sample shows igneous texture, pyroxenes with compositional zoning and has mineralogic and isotopic similarities to L ordinary chondrites.

Specimens: Fabien Kuntz holds the main mass. Three fragments weighing 34.04 g and a polished thin section are on deposit at App.

Data from:
  MB110
  Table 0
  Line 0:
Place of purchase:Tindouf
Date:P 2020
Mass (g):475.9
Pieces:1
Class:Achondrite (ungrouped)
Shock stage:strong
Weathering grade:moderate
Fayalite (mol%):25.9±1.5
Ferrosilite (mol%):18.2±0.9; 15.0±1.2
Wollastonite (mol%):2.3±1.1; 30.7±2.9
Magnetic suscept.:3.86
Classifier:A. Love, App
Type spec mass (g):34.04
Type spec location:App
Main mass:Kuntz
Comments:Submitted by Anthony Love
Plots: O isotopes:  
Institutions
   and collections
UNM: Institute of Meteoritics MSC03 2050 University of New Mexico Albuquerque NM 87131-1126 USA, United States; Website (institutional address; updated 12 Feb 2015)
App: Department of Geology, 572 Rivers St., Appalachian State University, Boone, NC 28608, United States (institutional address; updated 7 Mar 2013)
Kuntz: Fabien Kuntz, France; Website (private address)
Catalogs:
References: Published in Gattacceca J., McCubbin F.M., Grossman J., Bouvier A., Chabot N.L., D'Orazio M., Goodrich C., Greshake A., Gross J., Komatsu M., Miao B., and Schrader D. (2022) The Meteoritical Bulletin, No. 110. Meteorit. Planet. Sci. 1-4
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Photos:
CreditPhotos
Public domain photographs:
Anthony Love      
Geography:

Algeria
Coordinates:Unknown.

Statistics:
     This is 1 of 1246 approved meteorites from Algeria (plus 29 unapproved names) (plus 4 impact craters)

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