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| Northwest Africa 2800 | |||||||||||||
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| Basic information | Name: Northwest Africa 2800 This is an OFFICIAL meteorite name. Abbreviation: NWA 2800 Observed fall: No Year found: 2007 Country: Morocco Mass:  686 g | ||||||||||||
| Classification history: |
This is 1 of 293 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 |
Writeup from MB 93:
Northwest Africa 2800 Morocco 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: MB93 Table 2 Line 10: |
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| Institutions 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) |
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| Catalogs: |
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| References: | Published in Meteoritical Bulletin, no. 93, MAPS 43, 571-632 (2008)
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Geography:
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Statistics: This is 1 of 1973 approved meteorites from Morocco (plus 37 unapproved names) (plus 1 impact crater) | ||||||||||||