Goal: something is buried under nine miles of regolith, and something is guarding it. Dig, haul ore to the Assay Office, upgrade the rig at RigWerks, fix the hull at PumpJack or the Quartermaster, go deeper.
Watch the fuel. The white tick on the fuel bar is what the climb home costs; turn back before you reach it. Falling is free, right until you land.
Gems form inside gas pockets, with a few lying loose in deep dirt; gas hits harder the deeper you go. Geodes are the dull purple nodules. They can't be sold; the Lodechanter on the far right trades them for rig powers.

Drill by pushing into dirt while standing on it. Rock needs a tier-VI bit, a blast charge, or the Bedrock Bite lodechant. Magma and gas pockets bite; a radiator softens them. Ore stays visible through the ground, so plan the shaft. Bedrock seals the deep. Somewhere in the last row of dirt above it lies a Voltaic Core; it hums when you are close, and once mined the drill and hull take a coating that bites bedrock.