Northwest Africa 10171 (NWA 10171)

(Northwest Africa)

Purchased: Jan 2015

Classification: Martian meteorite (Shergottite)

History: The sample was discovered in the region of Laayoune Boujdour, and bought by Luc Labenne from an anonymous Moroccan from Zagora.

Physical characteristics: The stone is completely covered with a glossy fusion crust.

Petrography: (R. Hewins, S. Pont and B. Zanda, MNHNP) Pyroxene is prominent as large (up to 4 mm) massive or prismatic crystals. Pigeonite is intensely zoned and augite has a thin mantle of pigeonite. Pyroxene margins were subophitic to plagioclase laths. The feldspathic material is smooth, lacks cleavage or fractures. Locally it contains schlieren indicating flow. Raman spectroscopy on regions lacking schlieren indicated the presence of a dominant broad peak at 497 cm-1 characteristic of makelynite and suggesting high (>40 GPa) shock pressure (Wang et al., 2004). Accessories include ülvospinel and ilmenite.

Geochemistry: Mineral compositions and Geochemistry: (R. Hewins and S. Pont, MNHNP) Atomic Fe/Mn in pigeonite is 36 on average (n=143) and increases from 30 to 42 following the relationship of Karner et al. (2006, Fig. 6). Pigeonite is En₁₁Fs₃₈Wo₁₁ to En₆FsFs₇₃Wo_21. Subcalcic augite is En₄₇Fs₃₂Wo₂₁ to En₄₁Fs₂₁Wo_38. The feldspathic material is stoichiometric An_51-46Ab_46-49Or_3-5 and has the Raman spectrum of maskelynite.

Classification: (R. Hewins and B. Zanda, MNHNP) The meteorite has SNC Fe/Mn ratios and maskelynite of SNC composition. It is classified as a shergottite.