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Northwest Africa 11993
Basic information Name: Northwest Africa 11993
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 11993
Observed fall: No
Year found: 2006
Country: (Northwest Africa)
Mass:help 245 g
Classification
  history:
Recommended:  Ureilite    [explanation]

This is 1 of 472 approved meteorites classified as Ureilite.   [show all]
Search for other: Achondrites, Ureilites
Comments: Approved 9 Oct 2018
Writeuphelp
Writeup from MB 107:

Northwest Africa 11993 (NWA 11993)

(Northwest Africa)

Purchased: 2006 Sept

Classification: Ureilite

History: Samples were donated to Cascadia by Mr. Fred Olsen in July 2012.

Physical characteristics: Interior and slightly shiny exterior have a relatively uniform dark-gray color with occasional light reddish-brown patches.

Petrography: (A. Ruzicka, S. Goudy, Cascadia) Composed chiefly of olivine and pigeonite grains roughly 1 mm across, often separated by fine-grained materials, cracks, or Fe-hydroxide weathering product. No metal or sulfide minerals were found. Shock stage U-S4 (Stöffler et al. 2018)

Geochemistry: (A. Ruzicka, M. Hutson, Cascadia) Cores of olivine grains have ferroan olivine (Fa22.6±0.7, N = 38) and rims are more magnesian (Fa15.6±3.6, N = 9). Pigeonite (Fs17.1±3.8Wo11.1±3.5, , N = 28) shows less prominent magnesian rims.

Classification: Achondrite (ureilite). Silicate grain cores and rims were largely unaffected by weathering, but presence of hydroxide and reddish staining indicates some weathering occurred.

Specimens: A total of 20.6 g and 1 thin section are on deposit at Cascadia. Mr. McKenzie holds the main mass.

Bibliography:
  • Stöffler D., Hamann C., and Metzler K. (2018) Shock metamorphism of planetary silicate rocks and sediments: Proposal for an updated classification system. Meteorit. Planet. Sci. 53, 5-49. (link)
Data from:
  MB107
  Table 0
  Line 0:
Place of purchase:Denver
Date:P 2006 Sept
Mass (g):245
Pieces:1
Class:Ureilite
Shock stage:U-S4
Weathering grade:minor
Fayalite (mol%):22.6, 15.6
Classifier:A. Ruzicka, S. Goudy, M. Hutson, Cascadia
Type spec mass (g):20.6
Type spec location:Cascadia
Main mass:Mr. Ronnie McKenzie, Pretoria, South Africa
Comments:Specimen numbers RM-8 and CML0681.; submitted by Alex Ruzicka
Institutions
   and collections
Cascadia: Cascadia Meteorite Laboratory, Portland State University, Department of Geology, Room 17 Cramer Hall, 1721 SW Broadway, Portland, OR 97201, United States; Website (institutional address; updated 28 Oct 2011)
Olsen: Unknown person (private address; updated 17 Apr 2009)
Catalogs:
References: Published in Meteoritical Bulletin, no. 107, in preparation (2018)
Find references in NASA ADS:
Find references in Google Scholar:
Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 6438 approved meteorites from (Northwest Africa) (plus 2025 unapproved names)

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