There Should be a silver mineral added as the only way
you can get it is to find it from cargo pods but as for balance it should only be semi-rare or rare. You could also add in silver walls,doors etc.
Isn't Silver used as money in this game?
Indeed it is.
Yeah, but I agree that you should be able to mine it...considering that's how we get it now. Don't know if it'd work better as metal veins having a small chance to drop silver instead, or maybe 1-3 silver veins per map (if you want to spend the energy hunting them down through the whole cliff).
I think silver is better left as money. It isn't that good of a thing to build with, sure it makes super pretty things, but that's like objects. Silver pocket watches for state alchemists and stuff or just money! :P Silver walls might look shiny but that's a huge waste of silver. I don't think you should be able to mine this money either, if you do mine it, it must be a severely limited supply, so as to not break the economy. Which is kinda already broken because you can get nearly infinite amounts of money fast and easy.