I'm currently working on a game with some fairly similar mechanics as Rimworld. Now I'm looking for a fun mining system in which the player has to actually investigate his surroundings with his characters before he even knows what's hidden in the ground. I want the player to invest some of his time into the process of mining, at least in the beginning of the game. I've considered a couple of possible systems but I think I can do better, so that's where you guys come in :).

Things I've considered:

- Like with Dungeon Keeper you assign tiles that you would like to be mined and then on good look you will keep hitting more of the good stuff. The player has to continously update his mining plans as you will keep discovering more mineable tiles.

- Characters have to survey an area on the map. They have to specifically survey for the kind of resource they want to find in this area so it's important they pick the right spots to survey. These right spots can be discovered by recognizing the certain terrain patterns(like: rocky ground and water has more chance of having metal whereas swampy ground has more potential for peat) have a higher chance of having a kind of resource in the ground and by gaining hints from war and trade with natives.

You could find old mining surveys, but be unable to actually interpret them until you've done some mining yourself. Like "Okay, I think that thing represents the river, because it forks twice in quick succession like that river does. There's a bunch of glyphs over here and there, but I don't know what they mean, like does this one mean 'coal' and this sort of hat above it mean 'at the surface', or maybe 'a lot of' or 'not much of'..." You have to scout out the area and do some mining to test your hypotheses, and as your hypotheses are verified or fasified you gain the ability to read the maps (and thus not have to do so much manual investigation for the rest of the game).