Stand By, Ready
I can't seem to find this in the rules or maybe I just do not get it. So hopefully you guys can help me out.
I found a runestone (gear) in the Mine and wish to put it into my gun. So I go to the blacksmith but what does it cost (beside 1 darkstone) to get the procedure done?
You will find the rules on the left of page 19 of the rulebook under Item Upgrades.
Upgrades found in the mine may be added to an empty slot at the listed price or removed forfeiting the cost of adding them. This can be done at the beginning of any turn down the mine. (Possibly at other points as well but certainly when you chose what gear is active during a combat turn.)
Upgrades got from the Blacksmith are permanent and can't be removed.