MetSoc Home            Publications            Contacts  
Search the Meteoritical Bulletin Database
Last update: 3 Sep 2023
Search for: Search type: Search limits: Display: Publication:
Text help
Starts with
Sounds like
Falls  Non-NWAs
What's new
  in the last:
Limit to approved meteorite names
Search text:  
Northwest Africa 7657
Basic information Name: Northwest Africa 7657
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 7657
Observed fall: No
Year found: 2012
Country: Morocco
Mass:help 2.28 kg
Meteoritical Bulletin:  MB 102  (2013)  Mesosiderite
Recommended:  Mesosiderite    [explanation]

This is 1 of 256 approved meteorites classified as Mesosiderite.   [show all]
Search for other: Mesosiderites, Metal-rich meteorites
Comments: Approved 5 Feb 2013
Writeup from MB 102:

Northwest Africa 7657 (NWA 7657)


Purchased: Nov 2012

Classification: Mesosiderite

History: Purchased by Adam Bates from a Moroccan meteorite dealer, November 2012.

Physical characteristics: Two stones, irregular dark brown exterior with some metal and silicate visible in desert patina. Saw cut reveals ~50% bright metal patches in a light brown-gray silicate matrix, also a ~20 mm dark silicate clast containing fine-grained metal.

Petrography: (C. Agee, UNM) Microprobe examination of a polished mount shows approximately 50% silicates and 50% metal. Silicates dominated by pyroxene, but also ~25% anorthitic plagioclase, accessory silica, olivine, chromite, phosphate and troilite. Pyroxene shows lamellar exsolution, some plagioclase grains show euhedral forms, large pyroxene clast is riddled with fine metal veins and blebs. Metal is approximately 90% kamacite and 10% taenite, minor amounts of schreibersite detected.

Geochemistry: (C. Agee and M. Spilde, UNM) EMPA. Low Ca-pyroxene Fs27.9±3.1Wo3.2±0.6, Fe/Mn=27±2, n=17; high Ca-pyroxene Fs15.8±0.8Wo40.8±0.3, Fe/Mn=19±1, n=4; olivine Fa25.3±2.7, Fe/Mn=38±4, n=8, plagioclase Or0.3±0.0Ab8.6±0.6An91.1±0.6, n=6; kamacite Fe=93.03±0.46, Ni=6.49±0.25, Co=0.45±0.02 wt%, n=16; taenite Fe=60.89±1.83, Ni=38.60±1.75, Co=0.09±0.03 wt%, n=6.

Classification: Mesosiderite

Specimens: 48.1 g including a probe mount on deposit at UNM, Adam Bates holds the main mass.

Data from:
  Table 0
  Line 0:
Place of purchase:Morocco
Date:P Nov 2012
Mass (g):2280
Fayalite (mol%):25.3±2.7
Ferrosilite (mol%):27.9±3.1
Wollastonite (mol%):3.2±0.6
Classifier:C. Agee, UNM
Type spec mass (g):48.1
Type spec location:UNM
Main mass:Adam Bates
Comments:Submitted by C. Agee
   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)
References: Published in Meteoritical Bulletin, no. 102, MAPS 50, 1662, September 2015
Find references in NASA ADS:
Find references in Google Scholar:


     This is 1 of 1991 approved meteorites from Morocco (plus 31 unapproved names) (plus 1 impact crater)

Direct link to this page