"The presence of ice or water on these bodies is one of the most significant potential resources. This is so as solar panels on spacecraft can provide the power to simply convert water to hydrogen and oxygen for fuel. This idea of harvesting resources needed in space doesn't sound like such a bad idea considering the fact that it costs from $5,000-25,000+ per kg to ferry items into space.
Currently, there are two private companies pursuing asteroid mining, these are Planetary Resources and Deep Space Industries. NASA too is involved on several levels as it has awarded contracts to several companies including both Planetary Resources and Deep Space Industries for studies relating to relating to asteroid redirection." Uncover Michigan
The Heinlein novel linked to below is centered on Luna, not an asteroid but you get the idea. In Heinlein's book the Loonies used mass drivers to throw their ore production at Terra aiming for splash down areas at sea where the rocks could be harvested.
Space colonization must come to be commercially viable or it will just end in a whimper of some sort. pl