Gems & Which Node Drops Them

There are no gem rocks in Dragonwilds. Gems come out of the ordinary ore nodes you are already mining, as a chance drop on top of the ore, and the chance only exists once you have taken the Gem Prospector passive at Mining 16. Mine for fifteen levels and you will not see a single one, which reads as bad luck rather than a locked mechanic.

Because the gem rides on the node, the gem you get is decided by the ore you chose to hit. That makes this table a route planner rather than trivia:

Four of the six come off Ghornfell nodes, which is the region you have already cleared by the time the passive unlocks. If you want a specific low gem, you go back rather than forward.

Diamond is the awkward one. It only drops from coal, and coal is only in Fellhollow, so the gem sits behind the region that is also your permanent coal commute. If you are farming coal for bars anyway, diamonds accumulate as a side effect, which is the cheapest way to get them.

Dragonstone is the only gem with two sources, and they are the top two ore nodes in the game. Adamantite is the realistic one: the Umbral Sands has open-world nodes, while runite is confined to the endgame Scorned Wilderness.

Pickaxe requirements follow the gem's host node, not the gem. Opal needs only a stone pickaxe despite riding on copper, which normally wants bone, so the binding constraint is whatever opens the node.