Northwest Africa 13669 (NWA 13669)

(Northwest Africa)

Purchased: 2020 Dec

Classification: Martian meteorite (Nakhlite)

History: Purchased in December 2020 by Said Yousfi from a dealer near the Morocco-Algeria border and then acquired jointly by Mendy Ouzillou and Dustin Dickens.

Physical characteristics: This somewhat friable specimen was found in several pieces (total weight 139.2 g, comprising stones of 66.1 g and 21.4 g plus other smaller fragments). The two larger stones are partially covered by black fusion crust as are some of the fragments.

Petrography: (A. Irving, UWS and P. Carpenter, WUSL) The specimen has a cumulate texture with a mean grainsize of ~1.2 mm. It is composed of zoned augite, olivine, zoned ferropigeonite (with ferrosilite rims) and plagioclase together with accessory titanomagnetite (with octahedral ilmenite exsolution lamellae), chlorapatite, pyrrhotite and intercumulus mesostasis (consisting of K-rich glass with ferropigeonite microlites plus subhedral grains of titanomagnetite and chlorapatite). Olivine contains veinlets of very fine grained, inhomogeneous Fe-rich "iddingsitic" material with oxide sums ~89 wt.%, and augite contains rare glassy melt inclusions (surrounded by radial cracks).

Geochemistry: Augite (Fs_22.8-37.6Wo_40.5-34.9, FeO/MnO = 31-35, N = 5), olivine (Fa_72.3-74.5, FeO/MnO = 47-48, N = 3), ferropigeonite (Fs_56.4-61.8Wo_11.6-6.5, FeO/MnO = 33-34, N = 2), ferrosilite rim (Fs_70.9Wo_3.0, FeO/MnO = 34), plagioclase (An_34.3-37.2Or_3.3-3.0, N = 2), ferropigeonite in mesostasis (Fs_57.6Wo_11.7, FeO/MnO = 31), titanomagnetite (TiO₂ 6.8 wt.%, Cr₂O₃ 0.6 wt.%).

Classification: Nakhlite.

Specimens: 20.2 g including a polished mount at UWB; remainder with Mr. M. Ouzillou and Mr. D. Dickens.