NWA 7020 (CR2) – 18.8g


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Northwest Africa 7020 (NWA 7020)

(Northwest Africa)

Purchased: 2011 Feb

Classification: Carbonaceous chondrite (CR2)

History: Purchased by Blaine Reed from a Moroccan dealer at the Tucson Gem and Mineral Show in February 2011.

Petrography: (A. Irving and S. Kuehner, UWS) Fairly closely-packed, medium-sized (typically 0.4 to 0.7 mm) chondrules and rare fine-grained CAI in a red to brown stained matrix containing kamacite, pentlandite and possible cronstedtite-tochilinite (based on EMPA spectra). Some chondrules are partially rimmed by kamacite. CAI contain spinel partially rimmed by gehlenite and rare Al-diopside.

Geochemistry: Olivine (Fa1.8-58.1, n=8, Cr2O3 in ferroan olivine 0.34-0.42 wt.%, n=6), orthopyroxene (Fs1.3-1.5Wo0.7-0.9), subcalcic augite (Fs4.6Wo28.5), augite (Fs1.6-3.3Wo44.1-39.2). Oxygen isotopes (R. Tanaka, OkaU): analyses of acid-washed subsamples by laser fluorination gave δ17O -2.101, -3.022; δ18O 1.026, -0.014; Δ17O -2.643, -3.019.

Classification: Carbonaceous chondrite (CR2).

Specimens: The main mass is held by Reed. A total of 22.8 g of material and one polished thin section are on deposit at PSF.