Martian Shergotite Achondrite Meteorite - 6 g - (1)

Northwest Africa 12269 (NWA 12269) (Northwest Africa) Purchased: 2018 Jul Classification: Martian meteorite (Shergottite) History: Purchased in Ouarzazate, Morocco by Mohamed Aid in July 2018. Petrography: (A. Irving and S. Kuehner, UWS; P. Carpenter, WUSL) Relatively fine grained with intersertal texture. Composed predominantly of zoned clinopyroxene and maskelynite (some showing a curved, narrow lath-like habit) with accessory fine grained intergrowths of hedenbergite+fayalite+silica, Fe-Ti oxides, merrillite and pyrrhotite. Geochemistry: Subcalcic augite (Fs24. 8-41. 8Wo31. 4-24. 3, Fe. O/Mn. O = 30-33, N = 3) , ferropigeonite (Fs66. 9-73. 0Wo16. 6-16. 5, Fe. O/Mn. O = 41-43, N = 2) , maskelynite (An51. 9-53. 1Or1. 3-1. 2, N = 2) . Classification: Martian (shergottite, fine-intersertal) A thin section has been done to add more unique information to the article. Shergottites are mafic to ultramafic in composition. For the non-geology people out there, this simply refers to the mineral composition of the rock. Think of mafic as being shorthand for high in magnesium (Mg) and iron (F) . These rocks are predominantly made from minerals that crystallized at great depths in the martian crust. Such minerals would include olivines, pyroxenes and some plagioclase. In the case of this shergottite, we’re looking at all three minerals. The opaque minerals are mostly pyroxene with some olivine and the transparent ones are a type of plagioclase called maskelynite. This mineral is really neat because it looks like glass under different microscopic views, but it’s chemical composition betrays it as a member of the plagioclase family. The current hypothesis is that maskelynite recrystalizes from plagioclase after being subjected to high pressure in a very short amount of time. These conditions are created from large meteorite impacts that generate shock waves and melt the plagioclase. Consequently, maskelynite has been found at impact craters on earth as well .