A class of calcium-poor achondrite meteorite; also known as olivine–pigeonite achondrites. They consist mainly of millimetre-sized grains of olivine and pigeonite minerals enclosed in a matrix of carbonaceous veins, with some metal also present. They are named after the meteorite that fell at Novo Urei, Russia, on 1886 September 10. The ureilites are noted for their carbon content (1% in Novo Urei), much of which is in the form of diamond, possibly produced by shocks from impacts while in space. The ureilites probably originated within the solar nebula, which would make them the most primitive of the achondrites.
Subjects: Astronomy and Astrophysics.