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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 106 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 Meteoritical Bulletin, no. 110, in preparation (2021)
Find references in NASA ADS:
Find references in Google Scholar:
Photos:
CreditPhotos
Public domain photographs:
Anthony Love      
Geography:

Algeria
Coordinates:Unknown.

Statistics:
     This is 1 of 1110 approved meteorites from Algeria (plus 27 unapproved names) (plus 4 impact craters)

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