Xanathar’s says an adamantine weapon costs 500 gp more than a normal weapon of the same type, but it doesn’t discuss how to MAKE one. How much adamantine do you need to make an adamantine weapon? How long does it take? @JeremyECrawford #DnD #DnD5E The specifics of physically how much adamantine it requires isn't something we're worried about. It has a cost, there are crafting rules, DM's call beyond that. But a good quick gauge, particularly for all/mostly metal weapons, is the weapon's weight. You need about that much.
— Dan Dillon 👥 (@Dan_Dillon_1) January 28, 2020