Northwest Africa 13637 (NWA 13637)

Algeria

Purchased: April 2020

Classification: Lunar meteorite (feldspathic breccia)

History: The stone was purchased by M. Lyon from a Moroccan dealer in April 2020. Later a Hungarian collector imported the stone.

Physical characteristics: Originally an individual cuboid-shaped (2 × 2 × 1.5 cm) gray stone without fusion crust. The sample was covered with orange-brown desert sand. Different colored clasts and thin (<0.2 mm) black veins and cracks are presented on the surface of the stone. Cut surface reveals coherent black matrix material. Inside the matrix there are several shiny metal grains and many white, gray and green clasts. Few fine orange-brown material filled cracks transect the sample.

Petrography: (D. Rezes, CSFK) The meteorite is a complex and polymict lunar feldspathic regolith breccia with many glass spherules (<100 µm). Most of the spherules are intact from shock effects. Melt flow textures are not presented in the sample. The matrix is fine-grained (<100 µm). Clast types are in wide range, impact melt clasts are most common. Impact melt breccia, granulitic impact melt breccia, basalt, micro-gabbro, anorthosite and granulite clasts are presented too. Most clasts are fractured, diameters are up to 2 mm. Major mineral phases are olivine, pyroxene and feldspar. Accessory chromite, FeNi-metal (<0.75 mm), silica, ilmenite, troilite, apatite and baddeleyite are presented. Weathering products are FeNi-oxides, barite and calcite.

Geochemistry: (D. Rezes and M. Szabo, CSFK) Olivine Fa_24.9±6.8, Fe/Mn=86±21, N=22; pyroxene Fs_33.7±17.9Wo_14.2±11.1, Fe/Mn=58±13, N=76; plagioclase An_96.2±2.4Ab_3.7±2.4Or_0.1±0.2, N=50; Matrix average composition SiO₂=44.2±0.4, TiO₂=0.5±0.0, Al₂O₃=26.4±1.1, Cr₂O₃=0.2±0.0, FeO=6.0±0.7, MgO=10.1±0.7 CaO=13.1±0.6, N=3 (all in wt%); Glass spherules average composition SiO₂=43.3±3.7, TiO₂=0.3±0.1, Al₂O₃=26.1±1.8, Cr₂O₃=0.2±0.1, FeO=5.7±2.4, MnO=0.0±0.1, MgO=9.5±1.0, CaO=15.1±0.8, Na₂O=0.2±0.2, N=12 (all in wt%). Bulk composition: (K. Gmeling and Zs. Kasztovszky, KFKI) NAA+PGAA gave the following mean abundances: (in wt%) FeO 8.9, Na₂O 0.35; (in ppm) Sc 22.6, La 5.91, Sm 2.43, Eu 0.93, Yb 2.46, Lu 0.33, Hf 2.32, Th 1.98.

Classification: Lunar feldspathic regolith breccia

Specimens: 2.3 g on deposit at CSFK, D. Rezes holds the main mass (6.3 g) including one polished thin section.