Is the Leviathan porphyry economical? As a rule of thumb underground copper mining requires a grade of 1.25%. Open pit can make do with as little as 0.25%. Since we haven't seen the potassic core of the Leviathan porphyry yet it is pointless to speculate about economics at this time. Please don't forget that half the porphyry is on the east side of the IP survey area where there is no Jurassic cover rock. We haven't seen any of that yet either.