On the Gem homeworld, there was a Sapphire gem who had the uncanny ability to see the future. Her superior was Blue Diamond, and she was assigned three Rubies to protect her wherever she went. She predicted that the rebel Gems, consisting of Rose Quartz and her renegade Pearl, would be captured after they shattered seven Gems in battle - including herself. But, when the moment arrived, one of the Rubies refused to accept this future and shoved Sapphire aside from an oncoming attack, accidentaly fusing with her, becoming the first cross-Gem fusion. Blue Diamond was not pleased with this and sentanced both of them to be shattered, only for the two of them to escape and recide together. Eventually, they decided that they were more comfortable being fused together, and to this day have been the most stable fusion between Gems, known as Garnet.
Powers and Abilities
Shapeshifting: Garnet has been shown to use this for stretching her limbs, or transforming, like into Steven in one episode.
Rocket Gauntlets: Garnet can fire her Gauntlets off as rockets.
Future Vision: From Sapphire in the fusion, Garnet can see into the future. She can pass this ability on with lip contact.
Electrokinesis: Garnet is able to generate electricity from her gems. With this, she is able to power an arcade machine that had been unplugged.
Gauntlets: Garnet's weapon she can summon, which she uses for melee combat. By charging power into them, Garnet can enhance their size for more powerful strikes. Thanks to Bismuth, Garnet's gauntlets have been upgraded to include spiked knuckles, increasing the power of her punches.
Rebecca Sugar (Steven Universe's creator) stated that Garnet is easily the strongest Crystal Gem.
Lifted a falling car
Flipped a wrestling ring with one punch
Casually lifts and throws giant rocks
Knocked down a large pillar with one kick
Held back a charging Jasper
Sent Amethyst flying to the ground with the strength to leave a crater in the ground
Garnet once blocked lightning, which takes extremely fast reflexes.
Easily swims in lava
Got back up after being crushed in a building
Tanked getting crushed through rock
Shrugged off getting hit multiple times with a baseball bat
Gem Physiology: Gem bodies are fragile, and after sustaining enough damage they will disappear, leaving their gemstones vulnerable as they are forced to regenerate. Gems cannot regenerate if their gemstones are bubbled or contained in another object.
Gemstones: If a Gem's stones are cracked, it leads to them becoming corrupted beasts, making them less intelligent and more feral. If a Gem's stone is shattered completely, then the completely cease to exist.
Gem Fusion Stability: If Ruby and Sapphire disagreed, or argued and disputed, or fought in a way shape or form that got them emotionally unstable, they would unfuse. This would also happen if they were poofed.