Emeralds are a currency in the game. Emeralds can be used for many things such as skipping missions, reviving in runs, purchasing outfits, purchasing boosts, purchasing lures, purchasing vehicles, and many more items. They can be bought with real money, awarded in chests, quests, or be found in-game on a run.
The emerald is shiny bright green in color, it is shaped like a diamond with cut edges. In-game the emerald sprite glows pale green and the shape of the emerald is more or less the shape of a rectangular prism.
Real Money Emerald Shop