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.

For surveying: Depending on the tech level you're dealing with (or if you have ascending tech throughout the game) you could start with them having to do manual "mark one eyeball" surveys, actually assigning a survey task to the characters who must walk around. This could inform a 'mining area' overlay which shows regions of suspected resources (and perhaps a level of certainty on them). As the player techs up new survey options could become available, from soil analysis to ground penetrating radar.

As for actually exploiting the resources, one of my ideas for a roughly similar game (that admittedly focused on the mining part) awhile back was to have the player essentially need to build a small mining complex to do things properly. As in, once the resources are found they have to build a mineshaft opening. But that mineshaft opening, when worked, produces all sorts of stuff. Rock, dirt, and other tailings as well as ore. The tailings need to be hauled elsewhere (and any toxic parts of them disposed or they'll poison the area later, which may or may not affect the player). Ore needs to be processed, washed, and finally smelted. All of these require auxiliary buildings and transport infrastructure to do efficiently. The idea was to allow the player to decide where such activity would go on. Would they build an entire mining complex right over the resource? Would they have the processing stuff back at the main base and use high-volume transport to move materials back? Would they try and locate a mining center equidistant from several mines? Do they process the toxins for safe disposal or just dump them somewhere remote? Etc etc.

I think the player shouldn't have to invest many resources to determine if an area has no resources. I feel it would be frustrating if I had to randomly prod around to try to find a suitable location and each failure is costly, especially early on. Maybe more valuable late game resources cost more to find, but early game success shouldn't depend on getting lucky.

You could make it easy to find low resource mines. For example, an abandoned mine would be easy to find but wouldn't yield as many resources. More plentiful mines would be more difficult find. That would employ some sort of risk/reward system for locating resources.

I also don't think any hidden resource should be necessary in the early game. Having to delay getting my settlement established because I haven't found an essential resource sounds frustrating. A skilled player shouldn't be blocked on trying to find a hidden resource. You should be able to start building the essentials, make a few resource scouts, and have them scouting for potential mines while you build up the beginnings of your settlement.

I think it should be very clear to the player what probability a certain location has for having resources. For example, when you have a resource scout to survey a tile. When you hover over a tile before you click, It could show you the probability of finding resources on that tile based. Like rocky terrain has a higher probability for metal resources. As you upgrade your resource scouts, the probabilities will be more accurate.

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).