Chaos Emerald (InstanceTopic, 8)

From Compile Worlds

Chaos Emeralds are special jewels appearing in Sonic the Hedgehog games. Despite the name, they come in various colors. There are seven emeralds in each game; in the first game, the last one is hidden and impossible to collect, just to stop you going super, because collecting all seven lets you do that.

In addition to Chaos Emeralds, there are also fake emeralds (appearing in Sonic Spinball and Sonic Battle) which do not grant super power, come in only one color and don't necessarily have a set of seven, Sol Emeralds which exist in Another World as a parallel to the Chaos Emeralds, and the Master Emerald, which keeps Angel Island afloat and houses Tikal and Chaos.

In Sonic 3 & Knuckles, the Chaos Emeralds transform into Super Emeralds. They remain in this form for every subsequent game, but are then just called Chaos Emeralds again.