Asteroids made of undifferentiated silicates with carbon compounds and water (densities ~2.3gm/cc). They represent the primordial material of the Solar System from which planets accreted. Besides an aggregate of carbonaceous dust and hydrated silicates, they also contain chondrules, spherical blobs ranging in size from less than 1 mm to nearly 2 cm that have higher temperatures of melting than the surrounding material. Chemical analyses indicate that, except for volatile elements (H, He, Ne, Ar, N, etc.), the relative chemical proportions of rock-forming elements (e.g. Si, O, Mg, Fe, Ca, Al, etc.) in carbonaceous chondrites closely correspond to the relative proportions in the Sun.