The Power Gems, also called the Power Stones, are 7 green, energized minerals similar to the Chaos Emeralds found on Mobius. Properties of these precious jewels include increased all around powers such as the ability to increase the size of objects, and the ability to upgrade or power machines. Supposedly, it is one of the rarest occurring natural elements, second only to the Chaos Emeralds. Unlike the Chaos Emeralds, however, the Power Gems were produced artificially by Dr. Ivo Robotnik himself.
At some point in his efforts to take over Mobius, Dr. Robotnik created his Power Gems to serve as energy sources for his weaponry and technology. Due to an unknown fluke, the Power Gems temporarily transported Sonic the Hedgehog, Mighty the Armadillo and Ray the Flying Squirrel into an alternate zone; it apparently affected the flow of time as Sonic and Mighty reappeared almost instantly despite having experienced a longer time within the zone itself, and Ray, who was later found trapped within one if the Power Gems, experienced what seemed like mere hours to him over the course of nearly a decade.
Years later, Doctor Robotnik used a Power Gem to boost the power of the original Metal Sonic, which caused him to transform into Titan Metal Sonic v2.0. However, Knuckles also used the gem's power to enlarge himself, and defeated the robot. Despite this, Metal Sonic survived and repaired himself. He later located and fought Sonic, defeating him with ease due to having the Power Gem embedded in his chest. However, Metal Sonic sacrificed his life to save both Sonic and Tails after being convinced to surpass his programming, though his Power Gem survived being buried in lava from Mount Mobius. Metal Sonic's Power Gem was eventually recovered by the Royal Secret Service, but was captured by Dr. Eggman (formerly known as Dr. Robotnik) upon his uprising. Geoffrey St. John managed to steal Metal Sonic's Power Gem back and gave it to Sir Charles, who used it to help create the Metal Sonic Troopers and later build it into Metal Sonic when he was rebuilt as Shard, providing him with a steady source of power while also helping with self-repair.
Doctor Eggman retained one Power Gem from his predecessor's supply and decided to use it to improve his Metal Sonic v3.7 model by imprinting it with the combat data from all the previous Metal Sonic incarnations for Metal Sonic v3.7 to access. With the information granted by the Power Gem, Metal Sonic v3.7 engaged Shard in battle and managed to gain the upper hand, but eventually realized that the Power Gem was a weakness as well as an advantage. As such, it caused the gem to self-destruct, cracking Shard's gem core in the process.
- The Power Gems appear to be similar to the Power Crystals from the early Crash Bandicoot videogames, albeit green as opposed to purple.
- The Power Stones is also the name of the Deep Power Stones from the Sonic SatAM cartoon show.
- The Power Gems were an artistic liberty taken with the adaptation of Knuckles' Chaotix; they were never featured in the actual game.