Gems

"Gems" are a extra-terrestrial species of magical beings characterized by the 'gems' which every gem posses somewhere on their body. Their origins, history, and culture are at this point not well understood, although numerous small hints throughout the series imply the gems are an interstellar race which at one point maintained several outposts on Earth. But for unknown reasons they suddenly fled and left many of their artifacts to ruin, with the only Gems currently still on Earth being the Crystal Gems.

Regular Gems

 * Pearl
 * Steven universe .pngyst
 * Garnet
 * Lapis Lazuli
 * Rose Quartz
 * Peridot

Half-Gems

 * Steven

Fusion Gems

 * Opal
 * Sugilite
 * Alexandrite

Half-Fusion Gems

 * Stevonnie

Description
Gems generally take on the form of feminine humanoids, Gems appearance varies from Gem to Gem but their colors are mainly composed of the color palette of the gem they posses (e.g. Garnet is mainly red, Amethyst is mainly purple/violet). Gems are not actually biologically male or female, in fact their gems are capable of completely altering their physical form and shapeshifting them into anything they desire. The only gem with a confirmed gender so far is Steven, due to his half human parentage.

All Gems have the ability to summon weapons from their gems, as well as the mentioned shapeshifting, and the ability to fuse with each other to create more powerful Gems such as Opal and Sugilite. It appears that there are specialized abilities for each individual Gem as well, such as Garnet's abilities to swim in lava and generate electricity.

In the "Pilot" and "Cheeseburger Backpack," it is implied that the Crystal Gems are over a hundred years old. And in "So Many Birthdays" it was revealed that the Gems are immortal and cannot die of old age or food poisoning (though they can still be killed in battle, presumably if their gem is destroyed). It has also been revealed that when a Gem's body is badly injured, they will  retreat into their gems to regenerate a new physical form, the process can take weeks or longer. In "An Indirect Kiss" it was shown that if their gem is damaged, their body will go through deformities.

Culture

 * There are currently two known groups of gems, the Homeworld gems (of which Pearl, Garnet and presumably Rose are) and another as of yet unnamed group which is simply known as "the bad gems" (which Amethyst was a creation of and Peridot has an ambiguous connection to) the relationship between the two is unknown but presumably antagonistic, The "bad gems" had plotted to exploit Earth for unknown reasons, and, as seen in "On the Run", already had a foothold on the planet which they used to create new gems.

Rose wanted to protect the life on Earth from this and created the Crystal Gems. In the time between the founding of the gems and Steven's birth, it's heavily implied some sort of civil war or rebellion between the gems erupted and, in the aftermath, Earth was cut off from the rest of gem space and the "bad gems" defeated, but the presence of Peridot in "Warp Tour" would suggest otherwise.


 * Gems appear to be very technologically advanced, creating teleportation devices called warp pads and apparently spaceships.
 * Gem culture is quite different from human culture, given the Crystal Gems' confusion over seemingly everyday Earth things such as birthdays and video games.
 * The Gem culture is an ancient one, possibly pre-existing the human race.
 * Pearl points out in "Tiger Millionaire " that, as Crystal Gems, they are not allowed to use their powers on humans.
 * The Crystal Gems have their own written language which is inscribed on many of their temples and which was first seen in Steven's room in the pilot.

Broken and Corrupted Gems
In "Ocean Gem", Pearl reveals that not all Gems are good.

It was revealed in "Mirror Gem" that, most of the Gem Monsters that the Crystal Gems fought up until "Mirror Gem" were in fact either corrupted or broken Gems. It is currently unknown what causes them to be in this state.

It is possible that the Gems on Earth that have become monsters had the same goal as the Crystal Gems: Protecting humanity, but eventually lost their way and became corrupted.

The reason there are no other known Gems is because they all either turned into monsters and were killed, captured, and contained by the Crystal Gems, or are just not on Earth.

As of "Island Adventure", the monsters that have been previously encountered are corrupted gems, they are the following:
 * Centipeetle Mother ("Gem Glow")
 * Worm Monster ("Bubble Buddies")
 * Gem Cave Creature ("Arcade Mania")
 * Giant Pufferfish ("Beach Party", formerly Watermelon Tourmaline).
 * Ice Monster ("Monster Buddies")
 * Invisible Gem ("Island Adventure")

Reproduction
It has been confirmed by Rebecca Sugar that normal Gems don't have parents and that they don't naturally reproduce. Rebecca Sugar also confirmed that Rose giving up her physical form to give birth to Steven was extremely unusual for a Gem. This makes sense, as they are an immortal race and therefore breeding is not a priority. Gems also lack reproductive organs. Matt Burnett, however, has stated that this should not imply that romantic relationships can't exist among Gems.

In "On The Run" it is revealed that gems from the Gem Homeworld used a canyon on Earth, referred to as "Kindergarten", to create new gems; and that Amethyst was one such gem. The methods used to accomplish this are as of yet unknown, but it can be deduced that is most likely involved the large bacteriophage-like machines laying gems in the holes such as that which Amethyst claims was "Where I came from".

Trivia

 * In "Alone Together" Pearl comments that Steven may not be able to fuse because he's 'organic' this would mean that gems aren't carbon based life forms and are either most likely based on the gem they possess, or something entirely not yet known to humans.
 * In "Keep Beach City Weird!" it can be seen that Pearl has saliva, but since Gems do not require food to survive and there physical bodies have a mold-able nature, it's questionable how or why Gems would produce or need it. Tumblr_nea9m3hoq21r2u7p0o1_1280.png