The debris from these collisions, together with other leftover rubble, was either swallowed up in further collisions or was mostly herded into planet-free zones like the asteroid belt between Mars and Jupiter . Like a blast furnace used for making iron, most of the metal sank to the center of each planet and a thin, rocky crust formed on the surface. The crust material of these planets generally has much less metal than the raw ingredients of the solar system. Most crust is the equivalent of the slag, or discard, from a blast furnace, and there are just a few places near the Earth's surface where metal ores are concentrated enough to make mining worthwhile. The good stuff is deep within Earth's interior.
Some meteorites are nearly pure stainless steel, born in ancient supernovas.
Most of the asteroids are made of the same stuff as meteorites. They too are rich in useful metals and chemicals such as water and carbon, and hence their commercial potential. An example of the possible riches amongst this rubble of the solar system is the asteroid Amun. The orbit of this mile-wide object comes close to the Earth's orbit and, over millions of years, it could be a threat to the Earth. Before then, however, it is likely that mankind will have visited the asteroid and mined it away to nothing, because research indicates Amun is made from that primordial stainless steel.