There is a small bug with dragonstone amulets, if you try to use an uncharged dragonstone ammy with the fountain of heros while you have the amulet equipped it will look like it worked but when you go to right click it to rub it to teleport the option isn't there. So you have to unequip it first and then use it with the fountain to get it to actually charge.

Anyway, not a big deal but it seems to be a bug nonetheless.