Emerald shard (InstanceTopic, 8)

From Compile Worlds

Emerald Shards are the broken fragments of Chaos Emeralds and/or the Master Emerald. They're used as plot devices in order to justify Knuckles the Echidna and Rouge the Bat's gameplay in Sonic Adventure 2, and to draw out the plot line of Sonic Battle. Generally, they're useless unless they're formed together as a whole emerald, but by then they are no longer shards.