Meteorite, Allende. Type III Carbonaceous chondrite, magnification 50x. Polarized light micrograph of a section through a chondrule from a stony meteorite (chondrite). Meteorites are asteroids, chunks of space rock, which reach the Earth's surface. Chondrites constitute about 85% of all meteorites. They are characterized by the presence of chondrules, small spheres of silicate minerals that are usually only a few millimeters across. The study of meteorites provides information on the history of the solar system.