As said by others, element can be mines on specific asteroids on the Genesis 2 map. It’s pretty distinctive. The asteroids have an almost ascendant teal type shade to them, and the have basically glowing ascendant teal crystals. The crystals drop primarily Shards and Stone, with a small amount of element even on boosted resource single player game.
An Ankylo is you best best for collecting large amounts of Element. A melee buffed Mantis with high level picks may be able to do better, I’m not sure.
On crystal isles, check around the bubbles on monster island and u still dozens of crystals and they give you element. Also check up near top, there is a huge crystal forest that gives elemt. And make sure you hit the small crystals, not the ones that zap you.