"How? Well... adjusting to layman;s terms... it's a very expert area of course... you send out people and probes and enormous lights and you basically just take rock samples to give you an idea of what is going on down there, geologically speaking. You also measure the caves and note the roughness of the rock, because that tells you how the passageways were formed, which gives clues to their stability.
"And define 'minerals'. What you might call a rock could be a mineral; that does not give it value. All it has to be to be a mineral is not be an aggregate. There's always something to be found."