Northwest Africa 13679 (NWA 13679)

(Northwest Africa)

Purchased: 2020

Classification: Primitive achondrite (Winonaite)

History: The meteorite was purchased from a dealer in Morocco.

Physical characteristics: Brownish sandblasted fragment with some black fusion crust preserved. Large metal areas are exposed.

Petrography: The meteorite is composed of silicate-dominated regions crosscut by up to 8 mm wide anastomosing FeNi metal veins or pockets of metal at intersecting veins. Silicate regions show a recrystallized texture of 50 to 200 µm sized enstatite, forsteritic olivine, diopside, and sodic feldspar grains often joining at 120 degree grain boundaries. These regions contain 50 to 150 µm sized finely dispersed FeNi metal and troilite grains. Etched FeNi metal veins show Widmanstätten pattern with up to 2 mm wide kamacite bands. Rare schreibersite inclusions are present in the metal. Accessories include daubreelite and alabandite associated with troilite as well as chromite. Some secondary Fe-oxides ocurr on silicate grain boundaries and metal vein margins.

Geochemistry: olivine: Fa_1.3±0.3 (Fa_0.9-1.7, FeO/MnO=4±1, n=5); low-Ca pyroxene: Fs_7.2±0.2Wo_1.9±0.2 (Fs_6.8-7.4Wo_1.5-2.1, FeO/MnO=10±1, n=5); diopside: Fs_3.1±0.3Wo_45.3±1.0 (Fs_2.7-3.7Wo_45.2-46.5, FeO/MnO=7±1, n=5); feldspar: An_13.1±0.3Ab_83.4±0.3Or_3.6±0.1, n=6