From Granblue Fantasy Wiki
Rough Stone is a normal quest treasure from Lumacie Archipelago.
|Buy various items from the Treasure shop||5-15|
|Upgrade Revenant Weapons (step 1)||100|
- Chapter 13/39/52 Free Quest: The Fruit of Lumacie - 14 AP (1 to 5 a round, average 3, AP efficient)
- Chapter 13/39/52 Whiff of Danger - 20 AP (wooden chest, -characters only, 2-4 per quest)
- Chapter 15  Episode 3 (0 to 6 a round, you can get Swirl Amber here too)
- Drop from Normal and Hard Yggdrasil raids (wooden chest)