A rare type of stony meteorite. Because their average chemical composition is very similar to that of the Sun apart from the hydrogen and helium and there is a relatively high abundance of volatile material, carbonaceous chondrites are thought to represent some of the primitive, unprocessed material from which the solar system formed. They are made up of a matrix of carbon-rich minerals in which the chondrules are embedded. The water content can be as high as 20 per cent. The largest known example is the Allende meteorite.