Dark Gold is a quest item that can only be found in the Caves. It is called “dark” not because of its color (it doesn't differ from normal gold), but because it melts under daylight, making it useless on the surface.
Stats
Rarity: Quest item
Weight: 1
Stackable: Yes
Quest Item: Yes
Mechanics
Dropping on surface: When dropped on the surface (Dungeon.depth ⇐ 0), it immediately melts
Throwing on surface: Also melts immediately when thrown on the surface
Quest requirement: Used for the Blacksmith quest - requires collecting 15 pieces
Mining: Can be mined with the Pickaxe in the caves
Melting effect: When it melts, it produces a puff of smoke and displays a splash effect