I spent about 400 shovel / pickaxe charges in The Volcano to get the five invisible lava rocks. On the other hand, I got about two of each rare gemstone and fungus and parasitic plant, and I got a jade war axe.
More reasonable would be spending 150 charges, because what with the volcano going unstable and fighting the volcano elementals, I spent just about my whole adventure day in there to do that quest *once*.
More reasonable would be spending 150 charges, because what with the volcano going unstable and fighting the volcano elementals, I spent just about my whole adventure day in there to do that quest *once*.