Dragon stones cannot be used yet! They will come to use in the future Dragon Tombs update, which has been a work in progress of the developers for a very long time now. They will be essential to the Dragon tombs update. It is believed that they will be able to either open or be a part of an opening of a Dragon Tomb. There is a little bit more on the Dragon Tomb Items wiki page: https://empireminecraft.com/wiki/dragon-tomb-items/ We don't know much about these special items yet, other than I've got a few stacks just sitting around >_>
