CH Carbonaceous Chondrites

Northwest Africa 770 (20°20.80' N, 11°50.03' W)

Found June 2000
Carbonaceous chondrite (CH)

NWA 770. Image source:

An 18.1 g crusted stone was found north of Legaaida by a person prospecting for meteorites. Mineralogy and classification (T. Bunch and J. Wittke, NAU): similar to Allan Hills 85085 in texture, mineral modes (pyroxene/olivine = 3:1, Fe-Ni metal = 27 vol. %), and chondrule size (mean diameter = 23 μm), but with few "matrix lumps"; contains small, subrounded CAIs with pure gehlenite (MgO = 0.3 wt. %) and micron-sized perovskite; 80% of chondrules are cryptocrystalline, and consist of stoichiometric enstatite (FeO = 0.24 wt. %) and forsterite (FeO = 1.1 wt. %); rare refractory chondrules have Al-rich diopside cores with spinel inclusions and forsterite rims (FeO = 0.45 wt. %); metal grains average Ni = 6.1 wt. % and Cr = 0.47 wt. %; shock stage, S2; weathering grade, W1. Specimens: 3.2 g plus thin section, NAU; main mass with finder.

Northwest Africa 5130

Find: 2007
Carbonaceous chondrite (CH3)

History and physical characteristics: A 23 g stone with minor fusion crust was purchased in Morocco in 2007. Petrography (T. Bunch and J. Wittke, NAU): Consists of small (10 µm to 60 µm diameter) Mg-rich cryptocrystalline chondrules of enstatite (73 % of these chondrules, N = 45) and forsterite (27 %), larger chondrules (80-140 µm) and chondrule fragments of similar compositions and textures, chondrules that contain Fe-rich olivine, large PP, GO, and GOP chondrules, Cr-bearing kamacite and taenite, and sulfides. Rare plagioclase occurs as fragments and in chondrules.
Geochemistry: Small chondrule enstatite = Fs0.3-1.8Wo0.8; forsterite = Fa0.26.0, Cr2O3 mean = 0.56 wt%; cpx = Fs1.5Wo33, Al2O3 = 11.1 wt%. Fe-rich chondrule olivine = Fa25-42, Cr2O3 mean = 0.67 wt%, FeO/MnO = 100 to 115. Metal Cr content = 0.25 to 0.48 wt% and FeS Ni = 1.2 3.5 wt%. Plagioclase is An89-98. Feldspathic glasses in Mg-rich chondrules contain K2O up to 2.8 wt%. Classification: Carbonaceous chondrite (CH3).
Type specimen: A total of 4.6 g are on deposit at the Field Museum of Natural History together with the main mass.

NWA 5130. Backscatted electron image showing chondrules and chondrule fragments. Dark gray shade predominate indicating the Fe-poor nature of the meteorite.