#geologists

So I'm adding dwarves to my setting but not your typical short stubby fleshy dudes. But rather short stubby rocky dudes. There are three types of dwarves upper crust, mid crust, and lower crust. They grow at different levels in the earth's crust and are made out of different rocks depending on what's available at that level. Like if they're closer to the surface they're made out of rocks and gems and such that naturally grow at that level.

Small issue though I have no idea what grows- forms? At those different levels farther or closer to the surface and I also don't know in what amounts. What's rare and what's common? I imagine diamonds don't grow in the same place as amethyst.

If you guys could help me out it would be much appreciated!

P.s. I did try googling it first but I couldn't find anything.

P.p.s. a visual representation like a rock map or something would be nice but is not required.