From Dark and Darker Wiki
Rubysilver
There is currently one mineable material and that is Rubysilver Ore. These ores can be found through at the maps and can be mined by equipping pickaxe. It will take you multiple cycles of minning until you will be able to break it to harvest the ore.
These are then can be transferred to either Rubysilver Powder via service option of Alchemist or Rubysilver Ingot via Weaponsmith. Crafting these will cost 6 and 10 Rubysilver Ores respectively. After you have sufficient amount of materials you will be able to craft armor of your choice. (Currently there is no option to craft any weapons with this ore.) Rubysilver Ingot crafts heavy armors and Rubysilver Dust will craft leather and light armors.
Tips
Hitting the ore with multiple people will not effect the time it takes for ore to break and only one person will recieve 4-5 Rubysilver Ore.
Your character will be extremely vulnerable when mining so it is best to get to cover and clear the rooms before attempting to mine.