From Guild Wars 2 Wiki
Double-click to apply to an accessory, amulet, or ring with an unused upgrade slot.
— In-game description
| Mournstone Amulet
(Learned from: Recipe: Mournstone Amulet)
| Mournstone Earring
(Learned from: Recipe: Mournstone Earring)
| Mournstone Ring
(Learned from: Recipe: Mournstone Ring)
- Account bound versions were removed from loot tables as part of the November 7th, 2017 update. Players who obtained them as loot before that update may exchange them with various merchants for Black Diamonds.
- These were originally called "Black Diamond", but were separate from the Black Diamonds introduced through Heart of Thorns.