The crypto NFTs
Because a lot of buildings are made of stone, cement and dust, to build those NFTs which upgrade your buildings will require stone, too.
And not only buildings but various quests and events will require some stone.
In time, your buildings will require various reparations, too, otherwise new NFTs won’t be crafted. However, the decay is not designed to be an annoying thing (for example, repairing your base every few hours), but just another mechanic of the game.
If in the future we see that the stone is not used, we could make it part of the after-PvP base repairs.
From the second update, when we will diversify the items and blueprints, you will be able to gather some different resources from the stone quarry, like sand, which will be required for various recipes.