Gem Homeworld

The "Gem Homeworld", or "Homeworld", is the home planet of the Gem race. It was first mentioned in Mirror Gem.

Description
While little is known about the Gem Homeworld, it is clear that it is the original home of the Gem race. Its culture is unknown, though Lapis Lazuli states that it is more advanced than it was 6,000 years prior, possessing technology such as the Gem Warship and Gem Destabilizers. This advanced technology greatly contrasts the old and decrepit ancient Gem technology left on Earth.

Going by the information of the Kindergarten, the existence of Gem-controlled planets, and the rebellion led by Rose Quartz in order to protect Earth from the actions of her people and their leader, it would appear that Homeworld clearly has malicious intentions for Earth, and by extension, the entire galaxy. This could possibly mean they are a warlike species and are probably bent on wiping out carbon based life. Another possibility is that they simply don't care about non-gem life forms, seeing them as inferior. The Gems primarily came to Earth for the reasons of war and experimentation. Yellow Diamond is possibly the leader of the planet, or at least a high authority figure.

"Mirror Gem"/"Ocean Gem"
Lapis Lazuli desired to return "home", referring to the Gem Homeworld.

"Space Race"
Pearl mentions that the Galaxy Warp served as a method of transport to Homeworld. Pearl also wanted Steven to see Homeworld.

"Warp Tour"
The Gem Homeworld is mentioned by name, and Peridot comes to Earth from there. Homeworld's Warp Pad is repaired by Flask Robonoids in order for Peridot to perform a maintenance check. Upon her departure, Garnet destroys the Warp Pad with her Gauntlets, preventing travel to and from Homeworld.

"On the Run"
Amethyst reveals that Homeworld Gems created other Gems in a facility known as the Kindergarten. Amethyst, among many other Gems, is one of these creations.

"The Message"
Lapis Lazuli states that Homeworld is much more advanced, and doesn't understand any of it.

"The Return"/"Jail Break"
The Gem Warship, carrying Jasper, Peridot, and Lapis Lazuli, was sent from Homeworld. Its destination was Homeworld before it had crashed.

"Friend Ship"
The Ancient Gem Colony Ship is visited by the Crystal Gems. The ship was the fastest way to travel between Earth and Homeworld before the building of Earth's Warp Pads.

Inhabitants

 * Gems
 * Yellow Diamond

Former

 * Pearl
 * Garnet (Ruby/Sapphire)
 * Rose Quartz
 * Malachite (Lapis Lazuli/Jasper)
 * Peridot

Trivia

 * Homeworld invaded Earth and established Kindergarten about 6,000 years prior to the events of the show, but was driven off by the Crystal Gems' war of rebellion 5,000 years ago. Based on the numbers given, they occupied Earth for at least a thousand years.
 * Peridot was the first known Homeworld Gem to come to Earth since the war.
 * It is unknown if the planet has an actual name, as up to this point it has only been referred to as "Homeworld".
 * Pearl said that Earth was not a Gem-controlled planet, possibly inferring that some planets are under Gem occupation.
 * Later, in "Cry for Help", Peridot states that Earth is a part of the "Crystal System", suggesting that the Homeworld has incorporated its colonized worlds into a larger territorial body, as well as has categories for star and solar systems.
 * It is revealed in "On the Run" that Amethyst is not from Homeworld, and instead was created in the Kindergarten.
 * This makes her the first revealed Crystal Gem to be formed on Earth. This is not counting Steven, who was born instead.
 * All Homeworld gems wear a diamond on their outfit, instead of a star like the Crystal Gems. This fits in with Ronaldo Fryman's "Great Diamond Authority" theory.
 * Implied by Garnet in her verse of the extended theme, living as a fusion on Homeworld may be a practice that's looked down upon or seen as wrong, which would be the reason why she would side with the Crystal Gems in the rebellion.