Unusual large chromite crystals in the Saint Aubin iron meteorite

Abstract

In the Saint Aubin octahedrite, chromite crystals of up to 3 cm occur enclosed in the metal phase. They are twinned along [111] according to the spinel law and display pseudohexagonal shapes in cross-sections. The crystals are homogeneous and exhibit compositions close to pure chromite endmember. Vanadium is the only additional element observed in appreciable amounts of up to 0.73 wt%. Chromite in the Saint Aubin meteorite crystallized from liquids with very low amounts of Cr and O close to the Fe-FeS join as indicated by its composition and phase relations. The growth of large chromite crystals implies stable supersaturated conditions for a long period in the meteorite parent body of Saint Aubin.