The Blue Gem is a blue emerald cut gem, similar in appearance to a Sol Emerald, that can be equipped on Sonic's Custom Shoes. When used, it allows Sonic to use Mach Speed and dash forward as if the player hit a Dash Panel. However, if Sonic runs into a wall he will fall down being briefly immobilized, taking a short amount of time to get back up.
While having set Sonic's Custom Shoes to utilize the Blue Gem's ability, the Blue Gem changes their appearance into a blue pair of shoes resembling Sonic's 2G Hi-Speed Shoes.
- Official in-game description