Northwest Africa 17865 (NWA 17865)

Algeria   Purchased: 2025

Classification: Lunar meteorite (troct. anorth. melt breccia)

History: Purchased by Mark Lyon from a Northwest African meteorite dealer in 2025. Reportedly found in the Algerian Sahara.

Physical characteristics: Two identically appearing stone stones found in the same vicinity. The masses are 5951 and 4249 g. The exterior surfaces of these meteorites are irregular with cavities and vesicles present; they are dark gray in color with tan colored caliche coatings where they were buried in the desert soil. A full slice polished saw-cut of the 4249 g stone reveals an intricate pattern of cm-sized clasts set in a very fine-grained groundmass. The overall interior color is primarily pale olive-green.

Petrography: (C. Agee, UNM) Electron microprobe analysis and imagery indicate a brecciated and partially shock melted troctolitic anorthosite consisting of an anorthitic plagioclase-rich host that poikilitically encloses fine-grained olivines ~10-20 µm in size. Olivine and makes up approximately 20% of the modal mineralogy and anorthite makes up approximately 80% of the modal mineralogy. Pyroxene is rare. Many vesicles are scattered throughout this meteorite. Dominant accessory phase is troilite.

Classification: Lunar troctolitic anorthosite melt breccia. Olivine compositions are consistent with the lunar highlands Mg-suite.