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Northwest Africa 2800
Basic information Name: Northwest Africa 2800
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 2800
Observed fall: No
Year found: 2007
Country: Morocco
Mass:help 686 g
Meteoritical Bulletin:  MB 93  (2008)  Martian (shergottite)
Recommended:  Martian (shergottite)    [explanation]

This is 1 of 307 approved meteorites (plus 2 unapproved names) classified as Martian (shergottite).   [show all]
Search for other: Martian meteorites
Comments: Approved 14 Jan 2008
Revised 4 Aug 2008: final writeup
Writeup from MB 93:

Northwest Africa 2800


Find: July 2007

Achondrite (Martian, basaltic shergottite)

History and Physical characteristics: A 686 g stone was purchased in Morocco in July 2007 by an anonymous buyer. NWA 2800 is a complete and lightly weathered stone with significant desert ablation that has eroded most of the fusion crust and imparted a dull to shiny sheen to the surface.

Petrography: (T. Bunch and J. Wittke, NAU: A. Irving, UWS) This basaltic shergottite is very coarse-grained with ophitic to mostly subophitic texture with orientated elongated crystals together with prominent patches of pyroxferroite breakdown phases. Maskelynite long dimensions reach 6 mm and several pyroxene crystals are blade-like with dimensions of 7.3 × 0.4 mm. Pigeonite and augite show prominent {100} simple twinning, extensive sector compositional zoning and exsolution lamellae, in addition to shock lamellae. Patches of possible decomposed pyroxferroite contain symplectites of fayalite, silica and Fe-rich pyroxene with associated Cl-apatite, merrillite, ulvöspinel, ilmenite with included pyrrhotite, silica needles (up to 2 mm in length), and silica-rich glasses. Interstitial pockets of late-stage residuum ("chaotic" zones), which are typically contiguous to patches of pyroxferroite decomposition, consist of K-feldspar and plagioclase hopper and acicular crystals, clusters of anhedral fayalite grains, solitary euhedral fayalite crystals, silica crystals, and graphic intergrowths of silica and plagioclase, all of which are set in an inhomogeneous glassy mesostasis. Modal analyses in vol%: plagioclase (maskelynite) = 47; pyroxenes = 39; decomposed patches = 10; late stage residuum = 2 and oxides = 2.

Mineral compositions: Main body pigeonites are zoned (Fs38.7-Fs60.1; Wo10.2-Wo19.1; FeO/MnO = 33-41). Augite and subcalcic augite are zoned (Fs26.3-Fs69.1; Wo35.3-Wo23.3). Maskelynite shows a wide range of cation deficiency in stoichiometry in all analyses (An55.5Or0.6-An72.3Or3.8; [n = 25). Plagioclase (An73.9Or5.6) in graphic intergrowths and K-feldspar (Or59Ab31) hopper crystals. Symplectite fayalite (Fa94.7) and solitary fayalite (Fa89.3; CaO = 0.35 wt%) in chaotic zones.

Classification: Achondrite (Martian, basaltic shergottite). NWA 2800 is very similar in texture, mineral content, and phase compositions to the Los Angeles basaltic shergottite.

Type specimens: A total of 20.3 g is on deposit at NAU. The main mass holder is anonymous.

Submitted by: T. Bunch, NAU.

Data from:
  Table 2
  Line 10:
Place of purchase:Morocco
Mass (g):686
Type spec mass (g):20.3
   and collections
NAU: Geology, Bldg 12 Knoles Dr Northern Arizona University, Flagstaff, AZ 86011, United States; Website (institutional address; updated 12 Apr 2012)
UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012)
References: Published in Meteoritical Bulletin, no. 93, MAPS 43, 571-632 (2008)
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     This is 1 of 2012 approved meteorites from Morocco (plus 35 unapproved names) (plus 1 impact crater)

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