Stone accumulates automatically in your claimed Stone Quarries. To collect the accumulated stone, just touch the quarry. Arguably, of the four collectible resources, Stone is the second most valuable due to it's heavy use in upgrading walls.
The maximum amount of stone a dungeon can hold is 7,201,500:
- 4 x Warehouses at Level 10 (1.6M each)
- 4 x claimed Stone Quarries at Level 10 (200k each)
- Dungeon Heart (1.5k)
You can also earn stone by Raiding, and is dependent on how much damage you perform, and the level of your opponent.
There are several ways to spend stone: