Heh. You'll be swimming in diamonds and redstone before you know it, if you find a mineshaft and take time to explore it thoroughly. Whoever left them behind sure didn't spend a lot of effort to mine all the precious minerals out of it.
"Good grief. You guys sure know how to make something out of nothing. And then take sides about whether or not it's nothing, and then change your minds and discuss why you thought it was something." - Kestra