Aubrites belong to a group of meteorites called achondrites. This group of meteorites is different from chondrites in that they don’t contain chondrules, the silica-rich sphere like inclusions for which chondrites are known. Aubrites originated from asteroids and have a brecciated texture. This fragmented texture is the product of a violent collision between the aubrites parent asteroid and another asteroid.
Mineralogically, aubrites are very similar to enstatite chondrites. They are composed primarily of the magnesium rich pyroxene, enstatite. The big difference is that aubrites come from asteroids that heated to the point that they experienced melting and underwent some form of chemical change. In the geological sciences this is called differentiation. Another defining characteristic is the addition of the mineral oldhamite (1). This calcium sulfide, for reasons I’m not sure of, doesn’t form naturally in terrestrial rocks. This quality makes it a useful mineral in determining the celestial origin of aubrites.
1. Smith, Caroline; Russell, Sara; Benedix, Gretchen. Meteorites. Firefly Books. 2009. P. 68