Probably we're only going to be mining small Earth crossing asteroid that are close to Earth intercept in delta-v terms to start with.

Have you seen the reports on the new data coming out of the mission orbiting Bennu a few days ago? It's looking like small asteroids might be a bit less undifferentiated than we thought those the story isn't changing by that much.

https://www.space.com/asteroid-bennu-formation-history-osiri...