Northwest Africa 7208 (NWA 7208)

(Northwest Africa)

Purchased: 2010 Feb

Classification: Carbonaceous chondrite (CV3)

History: One stone was purchased by an anonymous buyer in Tucson, USA, in February 2010.

Physical characteristics: A 39 g stone covered with a brown-black fusion crust.

Petrography: (M.A. Ivanova, Vernad) The meteorite consists of fine-grained matrix, chondrules to 2 mm, and abundant refractory inclusions to several mm. One big (1.5 cm) dark inclusion was found in the section. Minor phases include spinel, chromite, magnetite, sulfides, and Fe,Ni metal grains in olivine. The dark inclusion consists of smaller chondrules (< 1 mm) and their fragments, isolated olivine grains, opaques embedded in a fine-grained matrix.

Geochemistry: Olivine Fa_0.44-35. Low-Ca pyroxene Fs_0.68-7.0Wo_0.9-4.8, plus augite and diopside in refractory inclusions. Olivine in dark inclusion is Fa_0.52-53 and low-Ca pyroxene is Fs_1.8-6.0Wo_0.4-2.71. Oxygen isotopic compositions: (I. A Franchi and R. C Greenwood, OU, by laser fluorination): δ¹⁸O = 1.038; δ¹⁷O = -3.465, Δ¹⁷O = -4.005 (all per mil). Oxygen isotopic composition of the dark inclusion is: δ¹⁸O = 5.16, δ¹⁷O = -0.32, Δ¹⁷O = -2.72 (all per mil).

Specimens: 8.23 g and one polished section are on deposit at Vernad. The anonymous buyer holds the main mass.