Unit weight: 15
Stone is produced by harvesting stone piles on the surface, or mined from a quarry. It is used in construction, for buildings, roads, bridges, and tunnels.
Although there is a limited amount of stone on the surface, you can build quarries to mine a lot more from the ground (although it takes a lot of workers for this). Quarries also only have a limited amount of stone in them, and once built, you cannot remove them, meaning that you will eventually run out of room.
Stone will always be available to buy through trading, so if you want to save space by not building quarries, then importing it is the best way to obtain it - otherwise you may regret using up the space for a quarry!