Cobalt is a negligibly useful resource due to its extremely high presence on asteroids. 

Though having some for domestic trade rarer elements like Rhodium and uranium are very useful.

Interestingly Carbon resources become useful for plastics and other polymer configurations, so crude oil and coal are still likely to be mined.

Large concentrations of phosphorus are vital as they only occur on planets (buried guano dumps are also vital for this reason), and potassium salts (potash) would also be vital. The ASM mines raw ores obviously but if we went to Urash it would either be for a very rare element or an unusually high concentration of vital resources IE. fertilizer components