Northwest Africa 10299 (NWA 10299)

Northwest Africa

Purchased: 2015 Feb

Classification: Martian meteorite (Shergottite)

History: One stone was purchased from an anonymous Moroccan dealer in Tucson, February, 2015.

Physical characteristics: The meteorite of 339 g has irregular shape, dark-brown spotted surface, and fusion crust is absent.

Petrography: (C.A. Lorenz, Vernad) The rock of coarse-grained subophitic texture, consists of an elongated prismatic grains of clinopyroxene (67 vol%, 0.7-3.0 mm) and interstitial prismatic plagioclase grains (23 vol%, 0.3-1.0 mm). Plagioclase is almost completely transformed to maskelinite, but several grains preserved the crystal structure at the grain edges. Pyroxene strongly fractured, twinned, with mosaic extinction. Plagioclase is almost completely maskelynitized. Fine-grained aggregate of silica and feldspar occur in interstitials between clinopyroxene crystals. Melt pockets of glass with bubbles are presented (5 vol%). Accessory phases are fayalite, sulfide, Ti-magnetite, ilmenite, chromite, apatite, baddeleyite. Weathering products are barite and calcite.

Geochemistry: Mineral compositions and geochemistry: (Borisovsky S.E., IGEM, EPMA) Pyroxene is Fs_23-79En_9-65Wo_7.4-35. The zoned pyroxene typically ranges from cores Fs₂₇En₃₃Wo₄₀ to rims Fs₆₈En₁₁Wo_19. FeO/MnO = 34.2 ± 5.1. Pigeonite, Fs_54±13En_31±14Wo_15±3 (in average, n=26); augite Fs_29±10En_40±8Wo_31±4 (in average, n=23). Plagioclase An_55±4Ab_43±4Or_2.4±1.8 (in average, n=17) and varies An_48-61Ab_38-51Or_0.9-6.3.

Classification: Martian (shergottite). The meteorite is moderately weathered.