Northwest Africa 11779 (NWA 11779)

(Northwest Africa)

Purchased: 2012

Classification: Ordinary chondrite (L6)

History: Purchased by Tomasz Jakubowski from Moroccan dealer in 2012; 40 g was cut off and analyzed as one thin section on petrographic microscope in polarized and reflected light, other one thin section was analyzed on microprobe; 16.5 g of sample was powdered and bulk chemistry was analyzed by ICP MS

Physical characteristics: Single specimen with partly preserved fusion crust.

Petrography: (T.A. Przylibski, K. Luszczek UTWroc) Rare chondrules, most with gradual transition to matrix. Only a few chondrules have sharp edges. Chondrules are identified as: BO, RP, PO, GO, PP. Some of them have rims up to 0.2 mm thick. Chondrule diameters are from 0.5 to 1.9 mm, average 1.2 mm. Some chondrules are up to 2.7 mm in diameter. Mesostasis is crystallized and matrix is corse-grained with olivine crystals up to 0.5 mm in diameter. Also feldspar crystals are clearly visible and some of them are polysynthetically twinned. Feldspars are from 0.02 to 0.15 mm large. Opaque minerals (around 10 vol.%) include troilite, kamacite and taenite, and rare chromite.

Geochemistry: (R. Kryza WrocU; T.A. Przylibski, K. Luszczek, UTWroc) Olivine Fa_24.9; pyroxene Fs_19.4Wo_1.3; chromite (Mg0.12 Fe²⁺0.71 Mn0.03 Zn0.01 Ti0.07)(Al0.25 Fe³⁺0.19 Cr1.56)O4; kamacite (5.7-6.7 wt%), taenite (up to 29.6 wt%), troilite without traces of Ni. Bulk chemistry (in wt%): Si 19.65, Al 1.19, Fe 18.45, Mg 15.51, Ca 1.52, Na 0.70, K 0.09, Ti 0.07, P 0.10, Mn 0.28, Cr 0.39, Ni 1.20, C 0.07, S 1.61; (in ppm) Ba 66, Co 306.7, Ga 4.6, Hf 13.9, Nb 0.8, Rb 2.1, Sn 18, Sr 24.7, V 74, Mo 0.8, Cu 82.1, Pb 0.2, Zn 20, Se 6.9, Zr 581.3, Au 126.5, Hg 0.11, Y 34.5, La 0.7, Ce 1.4, Pr 0.19, Nd 0.9, Sm 0.28, Eu 0.09, Gd 0.37, Tb 0.06, Dy 0.38, Ho 0.08, Er 0.22, Tm 0.03, Yb 0.2, Lu 0.03

Classification: Ordinary chondrite, L6, S1, W1