Pallasites contain big, beautiful olive-green crystals, a form of magnesium-iron silicate called olivine , embedded entirely in metal. Pallasites can show big variations. Sometimes the olivine does not occur as a single crystal but as a cluster and elsewhere it can create a pattern of veins through solid metal.
There are differing opinions as to how pallasites formed. Some scientists believe that they formed from melted asteroids, like iron meteorites. When an asteroid melts, the dense iron metal sinks toward the centre to form an iron core. Pallasites are thought to be samples of the boundary between this metal core and the silicate, olivine-rich mantle around it.
If this is the case, pallasites could potentially tell us a lot about the formation of the Earth and other terrestrial planets because they all have a similar structure. However, other scientists think that there are very few olivine-rich meteorites in the asteroid belt, and too many pallasites for them all to have come from a core-mantle boundary.