Northwest Africa 16300 (NWA 16300)

(Northwest Africa)

Purchased: Apr 2022

Classification: Ordinary chondrite (LL5)

History: Mr. Jasper Spencer purchased a single 326 g stone from a Mauritanian dealer in April 2022 via FB Messenger. The dealer told Mr. Spencer that the meteorite was found in Morocco in 2021. Mr. Spencer sent a 45.9 g end piece to Cascadia.

Physical characteristics: Physical Characteristics: The exterior of the end cut shows a glossy dark brown veneer with patches of darker remnant fusion crust. The cut face is medium-brown in color with darker brown halos around metal and sulfide grains.

Petrography: (M. Hutson, A. Ruzicka, Cascadia): In thin section, the sample consists of angular clasts, ranging from single angular grains up to a 4 × 4 mm rectangular clast. No complete chondrules are visible in the section; partial chondrules with poorly delineated edges are present in larger clasts. Clast boundaries are not sharply defined. Two clasts are surrounded by thin areas of opaque melt which connect to opaque veins which cut across the section. Only twenty percent of the olivine grains examined show weak mosaic extinction under cross-polarized light; the remainder have undulose extinction. Plagioclase feldspar grains are 30-50 μm across and have undulose extinction. In addition to olivine, low-Ca pyroxene and feldspar, phases observed include troilite, FeNi-metal, ilmenite, augite, chromite, merrillite, and chlor-apatite.

Geochemistry: Olivine and low-Ca pyroxene compositions are homogeneous. Olivine (Fa_30.4±0.6, N=43); low-Ca pyroxene (Fs_25.4±0.3Wo_2.1±0.5, N=27); plagioclase feldspar (Ab_85.1±0.7An_10.5±0.1Or_4.4±0.8, N=4).

Classification: Ordinary chondrite (LL5) based on texture, including size of plagioclase feldspar grains, and mineral chemistry.

Specimens: Cascadia holds 41.4 g in one piece, as well as a polished thin section and material in an epoxy butt; Mr. Jasper Spencer holds the main mass.