Composition is important. Most of Earths metal is in the core and completely inaccessible. However there appear to be some asteroids that are largely composed

Composition is important. Most of Earths metal is in the core and completely inaccessible. However there appear to be some asteroids that are largely composed of metal and are completely exposed. We mine about 3 billion tonnes of iron a year. A single iron rich asteroid could plausibly have hundreds or even thousands of times as much iron. https://en.wikipedia.org/wiki/M-type_asteroid https://en.wikipedia.org/wiki/M-type_asteroid