Northwest Africa 13572 (NWA 13572)

Western Sahara

Purchased: 2020

Classification: HED achondrite (Howardite)

History: A nomad found the 1650 g sample in three pieces Western Sahara. Samples were purchased by Carlos Muñecas (Expometeoritos) in Errachidia, with the help of Hmad Ait Hssain in 2020.

Physical characteristics: Samples occur as fragments from a larger, irregularly shaped mass. Exterior is coated in a layer or dark orange caliche. Dark wind ablated fusion crust coats approximately 30% of sample.

Petrography: Description and classification (A. Love, App) Polymict breccia composed of mm-sized, angular lithic and mineral clasts of eucrite and diogenite. Clast lithologies are: fine-grained basalts with zoned phenocrysts, recrystallized cumulate clasts, brecciated clasts, impact melt lithologies, pyroxene-rimmed Si clasts and diogenite mineral fragments and breccias. Additional minerals are: olivine, chromite, troilite, ilmenite and phosphates.

Geochemistry: (A. Love, App) Diogenite: Olivine, Fa_55.2±6.7 (Fe/Mn=50.3±1.8, Mg#=44.8±6.7, n=9); low-Ca pyroxene, Fs_27.8±3.2Wo_3.4±1.0 (Fe/Mn=30.3±4.5, Mg#=71.2±3.4 n=14); eucrite: low-Ca pyroxene, Fs_44.5±8.2Wo_3.7±1.1 (Fe/Mn=30.5±1.7, n=14); pigeonite, Fs_42.3±9.5Wo_12.9±10.1 (Fe/Mn=29.8±1.7, n=13); high-Ca pyroxene, Fs_26.6±12.0Wo_38.6±7.7 (Fe/Mn=27.3±3.3, n=13); plagioclase, An_94.1±1.2Or_0.1±0.1 (n=7).

Classification: HED achondrite (howardite M-S2, low weathering). Sample is an HED achondrite based on textures of clasts and Fe/Mn ratios in pyroxenes. Sample is a howardite based on subequal abundance of eucrite and diogenite.

Specimens: Carlos Muñecas (Expometeoritos) holds the 265 g main mass. A fragment weighing 22.24 g a mount and a polished thin section are on deposit at App.