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Northwest Africa 2907
Basic information Name: Northwest Africa 2907
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 2907
Observed fall: No
Year found: 2005
Country: (Northwest Africa)
Mass:help 586 g
Meteoritical Bulletin:  MB 91  (2007)  Achondrite-ung
Recommended:  Achondrite-ung    [explanation]

This is 1 of 125 approved meteorites classified as Achondrite-ung.   [show all]
Search for other: Achondrites, Ungrouped achondrites
Comments: Approved 28 Mar 2007
Writeup from MB 91:

Northwest Africa 2907

Northwest Africa

Find: 2005

Achondrite (ungrouped)

History: A large number of pieces were collected within a small strewn field of ~15 m in diameter in Algeria and sold in Erfoud, Morocco.

Physical characteristics: Most of the fragments composing the 586 g mass are without fusion crust, dark brown in color, and show extensive surface weathering.

Petrography: (T. Bunch and J. Wittke, NAU) Partially recrystallized polymict breccia that contains at least two distinct lithologies: a) medium-grained clasts (<2 mm) of untwinned orthopyroxene without discernible exsolution lamellae and a roughly equal amount of complex, polysynthetically twinned plagioclase partially converted to maskelynite; and b) medium-grained, partially recrystallized pigeonite with minor development of exsolution lamellae and twinning with inclusions of simple, albite-twinned plagioclase together with a fine-grained assemblages (<0.1 mm) of tridymite, metal, and plagioclase at recrystallization boundaries. Both lithologies are set in a fine-grained, partially recrystallized matrix of pyroxenes and plagioclase compositionally similar to lithologies (a) and (b). Minor minerals include Al-rich chromite, a sulfide phase, tridymite, phosphate, and metal.

Mineral compositions and geochemistry: Lithology (a): orthopyroxene (cores = Fs22.0–25.3Wo2.5; FeO/MnO = 24–27 with grain margins of Fs33.8Wo7.2 that in turn have exsolved Ca-rich pyroxene), plagioclase (An99.5Or0.5). Lithology (b): pigeonite (Fs38.1Wo11.1), plagioclase (An94.8Or5.6).

Classification: Achondrite (ungrouped); S3, moderate weathering. Overall characteristics of this meteorite are similar to clast material in some mesosiderites and may represent a large, separated mesosiderite clast.

Type specimen: A total of 23 g is on deposit at NAU. Reed holds the main mass.

Data from:
  Table 2
  Line 118:
Place of purchase:Erfoud, Morocco
Mass (g):586
Shock stage:S3
Weathering grade:moderate
Classifier:T. Bunch and J. Wittke, NAU
Type spec mass (g):23
Type spec location:NAU
Main mass:Reed
   and collections
NAU: Geology, Bldg 12 Knoles Dr Northern Arizona University, Flagstaff, AZ 86011, United States; Website (institutional address; updated 12 Apr 2012)
Reed: Blaine Reed, P.O. Box 1141, Delta, CO 81416, United States; Website (private address)
References: Published in Meteoritical Bulletin, no. 91, MAPS 42, 413-466 (2007)
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     This is 1 of 8904 approved meteorites from (Northwest Africa) (plus 1871 unapproved names)

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