There are two main categories of meteorites: stony and metallic. Each category is further subdivided into more detailed groups with similar characteristics. The Vestoids, for example, are all thought to have come from the asteroid Vesta, where, long ago, a powerful collision created shattered bits of Vesta that have been orbiting the solar system ever since. Chondrites are one kind of stony meteorite and they are often the oldest meteorites. Another category, the pallasites, have fascinating mixtures of stony and metallic material. Pallasites probably originated from boundary areas in larger asteroids, where rocky mantles were in physical contact with metallic cores.