A dragonstone amulet (u) is the unstrung version of the regular dragonstone amulet. It is made by using a gold bar on a furnace, while having a cut dragonstone and an amulet mould in the inventory.
Level 80 Crafting is required to make one, and crafting this item grants 150 experience. Stringing this item using a ball of wool gives 4 experience.
After it is strung, it can be enchanted into an Amulet of glory, which requires level 68 Magic and yields 78 experience. This is the highest level item that can be made with a dragonstone.