Found a cache of diamonds. They were buried under some dirt under a seam of diorite under the water flow from the spring, just to the side of the lava lake.
Some day I’d like them to be, I don’t know, just, like, on the surface? I mean if there’s any geological activity here (and the lava lakes point to yes) then theoretically some of the diamond caches would have gotten pushed to the surface occasionally.
Then again, they might be difficult to find under all the trees.
But still. This “down into the depths of the planetesimal just to grab some shiny rocks” thing is a bit old even for an experienced miner like me.