Stony-iron Meteorites The second major group of meteorites is that of the stony-irons. As their name suggests, stony-irons are mixtures of stone and iron. They are the smallest group of the three major meteorite types, and are divided into two groups. Mesosiderites   Mesosiderites are mechanical mixtures of metal and stone formed through collisions between asteroids. They have been called "the waste-basket of the Solar System", because they contain bits and pieces from many different types of meteorites. Mesosiderites probably formed relatively late during the major planetary aggregation episode, and trace the collisional history of Solar System materials. Pallasites   In contrast to mesosiderites, the other group of stony-irons, the pallasites, follow a similar evolutionary pattern to iron meteorites, having been formed through melting and differentiation. To return to the steel making analogy used for iron meteorites: if we could stop the smelting process before it was completed, then in the furnace would be a mixture of metal on its way down to the base of the furnace with slag floating to the top. Stony-irons are a network of iron-nickel metal in which are set iron, magnesium silicates (olivine), and are a snapshot, both in space and in time, of the planet-building process. Stony-iron like material inside the Earth Material like that of the stony-irons is thought to occur at the core-mantle boundary of the Earth. Again, as for the core of the Earth, we cannot access this region directly, so we must rely on stony-iron meteorites to help trace planetary differentiation processes. Pallasites are the most spectacular meteorites in terms of their appearance, looking very different from any terrestrial material.

Vaca Muerta was found in 1861 by a mining entrepreneur, who correctly identified it as celestial in origin. The name Vaca Muerta (span. for Dead Cow), stems from nearby geographical locations, and bears witness to the extreme dryness of the Atacama Desert (Chile).