Northwest Africa 12735 (NWA 12735)

(Northwest Africa)

Purchased: 2018

Classification: LL6-anom

History: Bought in Morocco in 2018

Physical characteristics: Brown stone. Cut face reveals dark gray interior.

Petrography: (J. Gattacceca, CEREGE) Recrystallized chondrite with olivine dominant over pyroxene. Plagioclase average size above 50 µm. Opaque are sulfides (indlcuding pentlandite) and magnetite. No metal was observed

Geochemistry: Olivine Fa_33.6±0.2, NiO 0.10±0.04 wt% (n=4). Orthopyroxene Fs_27.1±0.1Wo_1.9±0.2 (n=3). Plagioclase An_10.0Ab_84.8Or_5.3 (n=2). Oxygen isotopic composition (J. Gattacceca, C. Sonzogni, CEREGE) from analysis of one acid-washed 1.5 mg aliquot of a powdered 270 mg bulk sample is δ¹⁷O=4.01‰, δ¹⁸O=5.14‰, Δ¹⁷O=1.31‰ (linearized, slope 0.5247, analytical uncertainties 0.08‰, 0.12‰, 0.03‰ respectively).

Classification: Ordinary chondrite (LL6-anomalous). The anomalous designation is based on the Fa content of olivine, magnetic susceptibility, and the opaque mineralogy. The Fa content of olivine is higher than for typical LL chondrite: only 3 out of about 1800 LL chondrites have a higher Fa content (NWA 10462, NWA 11776, and NWA 12334, all classified as LL6-anomalous). Magnetic susceptibility is also lower than in other moderaltely weathered LL chondrites. The opaque mineralogy, featuring magnetite and pentlandite, is also unusual for a LL chondrite.

Specimens: Type specimen at CEREGE. Main mass with Labenne.