Beschreibung:
Ureilites are meteorites which show characteristics of primitive and differentiated meteorites. They are mainly composed of olivine and pyroxene. The pyroxene is in most cases pigeonite. In many ureilites, the silicate grains show a reduced, almost Fe-free rim. The amount of fayalite of unreduced olivines can differ greatly for each ureilite but is almost constant within a single ureilite. The silicate grains are embedded into a matrix material, the so called vein material. The vein material consists mainly of graphite, FeNi-metal (the so called vein metal) and fine grained interstitial silicates, mostly Ca-poor pyroxene. The vein material can also contain carbon modifications such as chaoite, lonsdaleite and diamonds. Ureilites are depleted in lithphile elements and show well equilibrated silicate grains, which is typical for a differentiated parent body ...