The Crystal Gems are the self-proclaimed guardians of humanity. The title, Crystal Gem, is what distinguishes them from the rest of their kind, a species of magical alien beings, known as Gems, with powerful gemstones affixed to their bodies.
The group currently consists of the following Gems: Garnet, Amethyst, Pearl, and Steven; and the fusion Gems: Opal, Sugilite, and Alexandrite. Each member wears a star symbol somewhere on their clothing - this likely existing as an indicator of one's role as a Crystal Gem. Though the pure Gems shown so far all have female-like qualities, Gems are a genderless race, with Steven being the first male Crystal Gem.
Known Gem Fusions
Other Known Gems
- Lapis Lazuli: A blue Gem who has the ability to control water.
All Gems have superhuman powers such as shape-shifting, object teleportation, weapon summoning, and Gem fusion. For thousands of years, the Crystal Gems have used these abilities to defend the planet Earth from countless magical threats. One of the Crystal Gems (and possible former leader), Rose Quartz, gave up her physical form to give birth to a half-human child, Steven Quartz Universe. Garnet, Amethyst, and Pearl consider Steven an important member of the Crystal Gems, and the three have taken it upon themselves to raise and teach him how to use his powers.
In several episodes, Pearl references that there are/were many more of their kind, but never elaborated on the absence of other Gems on Earth, implying that they all may have died or disappeared. In the episode "Ocean Gem," it is revealed that there are in fact other Gems, and that the monsters that the Crystal Gems fight to defeat are former Gems that had gone corrupt. As of now, only four Gems remain on Earth.
As revealed in ''Space Race'', there are more Gems on different Gem-controlled planets. The Galaxy Warp was the main hub that was used to travel off of Earth to different Gem planets, but currently all the warp pads are broken. This reveals why only the Crystal Gems reside on Earth.
- Pearl points out in "Tiger Millionaire" that, as Crystal Gems, they are not allowed to use their powers on humans.
- Wearing a star on one's outfit seems to be the emblem of the Crystal Gems.
Gems are not biologically male or female, or have female and male designations amongst themselves. The ones shown so far appear feminine and use feminine pronouns, with Steven being the first male due to his human half. The Gems' usage of gendered pronouns with one another does not deter the fact that they are all just Gems, first and foremost. Rebecca Sugar had stated that Gems in general have a 50/50 chance of using pronouns.
- List of known Gems and their ties to birthstones (by month). 
- From dialogue in "Ocean Gem", it is confirmed that Gemkind is different than the Crystal Gems. The Crystal Gems are simply the team of Garnet, Amethyst, Pearl, and Steven, while the species itself are just known as Gems.
- All of the Crystal Gems' weapons (including Steven's shield) have the same color scheme as their gem.
- Steven is the only member of the Crystal Gems whose skin isn't the same color as his gem, though his skin still exhibits a pinkish hue.
- The gems themselves correspond with the Gems personalities.
- Amethyst is a birthstone associated with love. The stone itself is associated with Dionysus, the god of wine and intoxication. Amethyst is not a clear thinker but is fun-loving.
- Pearl is a stone associated with purity. Pearl is a mature, wise, and perfectionist person.
- Garnet is a stone that protects from evil. Garnet is the most powerful of the Crystal Gems and often saves the day. She is also the leader of the Crystal Gems.
- Rose Quartz is associated with love and joy. Steven is the most caring, and upbeat of the gems, and Rose Quartz is mentioned to have been very loving of everything.
- Lapis Lazuli is associated with gods and power. She is a powerful Gem, nearly capable of defeating the Crystal Gems.
- Their gem placement seems to correspond to their personalities, actions, and how they think.
- Amethyst's gem is over her heart; she tends to be fun loving, and often does whatever she wants.
- Pearl's gem is on her forehead; she tends to over-think things and be a perfectionist.
- Garnet's gems are on her hands; she tends to not talk often and respond through action instead.
- Steven's gem is over his stomach; he tends to go with his gut instinct and is often hungry.
- It is revealed by Pearl in "So Many Birthdays" that gems don't age, but can still die if they are hurt badly enough and are not treated.
- This trait does not apply entirely to Steven.
- While Gems can't die from food poisoning, they can still get sick to the point of vomiting.
- This does not apply to Steven, as he is a hybrid of a Gem. This is demonstrated in "So Many Birthdays," Steven accidentally ages to the point of near-death.
- All Crystal Gems to have stars located somewhere on their outfits.
- Steven: on his t-shirt.
- Garnet: on the chest area of her body suit.
- Amethyst: star-shaped holes on her leggings.
- Pearl: on her shirt.
- Opal: on the draping section of her shirt.
- Rose Quartz: star-shaped hole on the stomach area of her dress.
- Sugilite: ragged, star-shaped holes on her leggings and painted on her nails.
- Alexandrite: special four-pointed star-shaped cutouts on her leggings and star-shaped hair.
- Even though all the Gems have the ability to shapeshift, Amethyst, Steven, and Garnet are the only ones shown demonstrating it so far, with Amethyst performing the ability the most.
- Steven may never develop the ability to shapeshift in the same way the Gems do because his body is physical, whereas a Gem's body is more of a "projection" on the physical plane.
- It is revealed in "Giant Woman," that the Gems are able to fuse together into even more powerful Crystal Gems. Here are the ones shown so far:
- It is revealed in "Steven the Sword Fighter" that Crystal Gems retreat to their gem and lose their physical form when badly injured. It is unknown how long it usually takes for Crystal Gems to regenerate as Pearl's regeneration took about two weeks. Also, when Crystal Gems regenerate their bodies, they can get a new outfit as shown in the aforementioned episode.
- According to Rebecca Sugar, Gems do not need to eat or sleep, but they can enjoy doing so anyway.
- If multiple gems stay fused for too long or have a fusion with an unstable personality, they can slowly lose their individuality. A prime example is the fusion gem Sugilite from the episode "Coach Steven."
- All of the Gems weapons are medieval: Garnet has gauntlets, Pearl has a spear, Amethyst has a whip, Steven has a shield, Lion has Rose's sword, Opal has a bow and arrows, and finally Sugilite has a flail.
- The Gems themselves seem to correspond with the Crystal Gems personalities.
- Rebecca Sugar had said that Gems have a 50/50 change of using gendered pronouns.
- This is done regardless to what Gems identify as, as Gems don’t have gender designations amongst themselves.
- This is demonstrated in "Ocean Gem", as Pearl called Lapis a "she".
- Rebecca Sugar confirmed that each of the Crystal Gems is based off of one the stages of the human emotional development spectrum 
- Steven is codependent
- Amethyst is counterdependent
- Pearl is group-dependent
- Garnet is independent