Chondrites and Achondrites Stony meteorites are by far the most common. They can be divided into chondrites and achondrites. Both types are composed mostly of silicate minerals, but the great majority also contain metallic iron in small-scattered grains. Chondrules are not found in terrestrial rocks. These chondrules, along with small mineral grains, accreted to form asteroids during the birth of the Solar System.
Chondrites are, by far, the most abundant type of stony meteorite.
Less common, comprising only a few percent of all meteorites, are achondrites. These are also stony meteorites composed primarily of silicates, but these meteorites have experienced familiar geologic processes of melting and differentiation - although these happened long ago. Most achondrites formed on asteroids during the birth of the Solar System, but a small number formed on Mars and the Moon. Stony-iron meteorites form in places where metal and silicate are mixed. Pallasites probably form when the olivine-rich mantle of an asteroid mixes with the metallic core.