Northwest Africa 12578 (NWA 12578)

Morocco

Purchased: 2018 Apr

Classification: Ordinary chondrite (LL6)

History: One fresh-looking crusted piece was purchased in Zagora, Morocco, by Sergey Vasiliev from a Moroccan meteorite dealer in April 2018. After purchase, the piece was broken into 2 pieces.

Physical characteristics: Total mass of one piece is about 415 g. Fusion crust is partially preserved. The interior of the meteorite is greenish gray whereas surface is dark brown.

Petrography: (Pavel Yu. Plechov, FMMR). Olivine and Low-Ca pyroxene are equilibrated and chondrules are indistinct or absent. Rare relics of barred-olivine chondrules have size from 500 to 700 µm. Low-Ca Px grains have rounded shape (size 150-250 µm) and very uniform composition (about Fs₂₅). Metal consists of kamacite and taenite (with 44-45 wt.% Ni). Plagioclase grains (An_10.6) are about 50 μm or more. These features indicate petrological type 6 for the meteorite. Olivine has no undulatory extinction, and the absence of opaque shock veins and melt pockets indicates a shock stage of S1. Olivine, pyroxene and metal are fresh and unweathered (weathering grade W0).

Geochemistry: Mineral composition and Geochemistry: EDS-WDS analyses (Pavel Yu. Plechov, FMMR). The primary chondrite paragenesis includes olivine Fa_30.59±0.22 (N=20), orthopyroxene Fs_24.9±0.4Wo_2.34±0.14 (N=18), plagioclase Ab_84.7An_10.6Or_4.3 (N=8), Cr-bearing clinopyroxene En_46.0Fs_10.8Wo_43.1 (N=5), chromite Crt_77.9Spl_8.9 (N=4). Phosphates are both Cl-apatite and merrillite. Composition of kamacite (in wt.%, N=3): Fe 88.8, Ni 4.2, Co 7.0 (measured by WDS). Taenite (N=2) contain 44.5 and 2.1 wt.% of Ni and Co respectively. Troilite is close to ideal FeS.

Classification: Ordinary chondrite. LL6, S1, W0.

Specimens: Sergey Vasiliev holds one piece about 240 g. Another piece (166 g) and thin section, FMMR.