Northwest Africa 12533 (NWA 12533)

Morocco

Purchased: 2018 Apr

Classification: Ordinary chondrite (H4/5)

History: A 220 g fragment of the meteorite was purchased by Curtis Bing from a dealer in the US (April, 2018). The dealer brought the sample in Marrakech, Morocco. The stone was a broken fragment surrounded by fusion crust. A polished thin section was carefully prepared from the fragment and subsequently examined using optical microscopy to identify the texture and mineralogy and electron microprobe for the mineral chemistry.

Physical characteristics: One piece. The color of the meteorite is pale brown.

Petrography (I. Baziotis, AUA): Textural observations of the thin section in both transmitted and reflected light showed that it is chondritic. It contains porphyritic and nonporphyritic chondrules, both Type I (Mg/(Mg+Fe)<90). The porphyritic olivine (PO) chondrules have rounded to oval shape ranging from 300 to 500 µm. The PMD for olivine is <5% (0.25). The PMD for low-Ca pyroxene is <1%. Both monoclinic and orthorhombic pyroxene are present. The groundmass consists of olivine, low Ca-pyroxene (orthopyroxene and pigeonite), high-Ca pyroxene, plagioclase and rare phosphates (merrillite). The olivine and plagioclase show sharp extinction, indicating shock stage S1. Shock veins were not observed. The rock matrix is cross-cut by numerous interconnected opaque veins. Black fusion crust covers the sample. Red-brown oxidation is visible on the exterior surface, around metal grains on cut surfaces and within the matrix.

Geochemistry: Feldspathic chondrule mesostasis Ab_87.6-82.8. High-Ca Pyroxene Fs_6.1±0.7Wo_45.1±1.1 (n=18).

Classification (I. Baziotis, S. Xydous, AUA): Ordinary chondrite (H4/5, W2, S1).

Specimens: 20 g at NHMV