and at higher levels of upgrading you can maybe customise it. hot/cold for IRON, but who cares about fossils.
at a lower level it can be sensed to ores, tech/fossils/coal, and it cant sense gems.
higher level, can sense gems.
higher level, can single out tech/fossils/coal for inclusion or exclusion,
higher level, can single out copper/iron/silver/gold/titanium for inclusion or exclusion,
higher level, specific gems.
but never make the resources glow, or give a direct "turn left 47 degrees and walk 5 blocks forward" way of finding it. i like the hot/cold, helps you find it, but doesn't point you right to it.