In this talk, J. L. Galache mentions that asteroid miners are looking for NEAs with:
- low delta-v (so the asteroid is easy to get to/from from Earth)
- low synodic period (for frequent launch/return-windows)
- low albedo, i.e. dark
I don't understand the last point. The low albedo is apparently thought to be correlated with a carbonaceous and water-rich composition. Why? Are there some good resources about this stuff online?