Northwest Africa 15189 (NWA 15189)

Ouargla, Mauritania

Find: Oct 2021

Classification: HED achondrite (Eucrite, polymict)

History: TKW: 516g - 5 individual Stones. Found: Ouargla, Algeria early 2021 by anonymous finder. Purchased in Algeria by Younes Chaoui in october 2021. Purchased by Gemma Thomas from Younes Chaoui March 2022 and sent for classification at UPlym.

Physical characteristics: Five weathered stones with some pale crystals visible at the surface. The sample does not preserve a fusion crust, and instead displays desert varnish across the majority of each stone.

Petrography: Polymict eucrite breccia with at least three distinct basaltic eucritic lithologies preserved, composed predominantly of plagioclase (48.5 vol%), low-Ca pyroxene (31.0 vol%), and high Ca-pyroxene (15.4 vol%), with accessory silica phase (3.0 vol%), troilite, chromite, ilmenite, Fe-metal, and zircon. A minor amount of diogenitic pyroxene (Fs<32, <10 vol%) entrained in the matrix. Clasts are relatively rounded and measure up to 5.4 mm in size. Matrix preserves abundant areas of melt with fine dendritic intergrowths of pyroxene and plagioclase. Ca-weathering products infill fractures and barite is present throughout.

Geochemistry: Low-Ca pyroxene Fs_33.3-67.3Wo_1.7-9.2, mean Fs_59.1±6.9Wo_4.0±1.9 (n = 95). High-Ca pyroxene Fs_18.6-69.3Wo_12.0-44.4, mean Fs_34.8±9.9Wo_34.9±10.1 (n = 100). Plagioclase An_77.3-96.7Or_0.0-10.2, mean An_92.4±2.9Or_1.1±1.5 (n = 86). Chromite Chm55.5-81.4Usp5.6-37.4, mean Chm72.0±8.0Usp17.6±10.3, Cr#87.6 (n=18). Fe/Mn = 32.1.

Classification: Eucrite Polymict

Specimens: 5 individuals including type specimen. Type specimen 22 g with UPlym. Main mass is with main mass holder Gemma Thomas 4 stones: 132, 99, 110, and 150 g