Asteroid Mining

Asteroids (in our belt) are the most common source of raw material. They can be mined and transported more easily than a similar volume of mass extracted from a planet. Asteroids are very valuable and small ones can contain billions of tons of raw material. For this reason, individual prospectors, small and large development corporations are keen to profit from resources like nickel, iron, platinum and iridium. Water ice and ammonia are also useful.

Asteroids may be collected and moved as a whole towards central processing locations. Gravity tugs can be used to pull them. Small ships may land on the surface and construct thrusters and processors on the surface from material mined there, turning the asteroid itself into a ship which flies to its destination.

They may also be broken up into smaller sizes to make mining and collection more manageable.

An effective way of performing large-scale mining operations such as mining an entire moon or asteroid belt would be by Von Neumann probes, taking advantage of their exponential growth. They could move on towards neighboring systems forever, seeking out raw materials (extracted from asteroids, moons, gas giants, etc.) making them the most efficient forms of mining operations possible.

Working-class humans in the The Expanse that mine asteroids are called the "belters".