Meteoritical Bulletin: Entry for Northwest Africa 13218

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Northwest Africa 13218

Basic information

Name: Northwest Africa 13218
This is an OFFICIAL meteorite name.
Abbreviation: NWA 13218
Observed fall: No
Year found: 2014
Country: (Northwest Africa)
Mass: 368 g

Classification
history:

Recommended:

LL3.2 [explanation]

This is 1 of 21 approved meteorites classified as LL3.2. [show all]
Search for other: LL chondrites, LL chondrites (type 3), Ordinary chondrites, and Ordinary chondrites (type 3)

Comments:

Approved 5 Apr 2020

Writeup

help

Writeup from MB 109:

Northwest Africa 13218 (NWA 13218)

Northwest Africa

Purchased: 2014

Classification: Ordinary chondrite (LL3.2)

History: Purchased from Morocco November 2014.

Physical characteristics: Seven matching stones, dark brown weathered exterior, no fusion crust, sawn surface reveals densely packed chondrules of variable size.

Petrography: (C. Agee, UNM) Microprobe examination of a polished mount shows numerous unequilibrated chondrules, many are porphyritic, apparent mean diameter 625±330 μm n=24. Abundant opaque matrix, most chondrules with glass or mesostasis. Aluminous augite, Fe,Ni-metal, and sulfide present.

Geochemistry: (C. Agee, UNM) Chondrule olivine Fa_17.2±9.2, Fe/Mn=52±19, Cr₂O₃=0.13±0.13 wt%, range Cr₂O₃=0.02-0.70 wt%, CaO=0.08±0.07 wt%, n=31; low-Ca pyroxene Fs_9.7±8.7Wo_0.6±0.4, Fe/Mn=20±19, n=6.

Classification: Ordinary chondrite (LL3.2), transitional between type 3.2 and 3.15 based on ferroan olivine mean Cr₂O₃ content and sigma from Grossman and Brearley (2005).

Specimens: 20.6 g on deposit at UNM, Larry Atkins holds the main mass.

Bibliography:

Grossman J.N. and Brearley A.J. (2005) The onset of metamorphism in ordinary and carbonaceous chondrites. Meteorit. Planet. Sci. 40, 87-122. (link)

Data from:
  MB109
  Table 0
  Line 0:

Place of purchase:	Morocco
Date:	P 2014
Mass (g):	368
Pieces:	7
Class:	LL3.2
Shock stage:	S1
Weathering grade:	W2
Fayalite (mol%):	17.2±9.2
Ferrosilite (mol%):	9.7±8.7; 12.2±7.9
Wollastonite (mol%):	0.6±0.4; 33.4±7.3
Classifier:	C. Agee, UNM
Type spec mass (g):	20.6
Type spec location:	UNM
Main mass:	Larry Atkins
Comments:	Field name LA-103; submitted by C. Agee, UNM

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)

Catalogs:

References:

Published in Meteoritical Bulletin, no. 109, in preparation (2020)

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Geography:

Coordinates:

Unknown.

Statistics:
This is 1 of 8495 approved meteorites from (Northwest Africa) (plus 1899 unapproved names)

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