Unknown Gems

Unknown Gems are Gems who have been visually shown through holograms, drawings, named, or other methods but have not been identified by their name or Gem type.

"Historical Friction"
In Steven and Jamie's play, "Beach City or Bust", props for a Crystal Gem fusion and Corrupted Gem Monster can be seen. Not strongly resembling any other fusions, this is a fusion between some (or all) of the Crystal Gems. This fusion fights off a Corrupted Gem resembling both the Centipeetle Mother and the Big Bird.

"When It Rains"
There are holograms of many unknown Cluster Gems in The Prime Kindergarten Control Room in "When It Rains".

"The Answer"
There are many unknown Gems (represented in silhouettes during Garnet's flashback) in "The Answer". These Gems make up Blue Diamond's court.

"Same Old World"
There are a few unknown Gems featured in Lapis' flashback.

"Monster Reunion"
There are a few unknown Gems featured in Centipeetle's flashback.

"Bismuth"
These are the "other Crystal Gems" who were mentioned by Bismuth, except for Nephrite, who is most likely a Homeworld Gem. They appear to be her close friends. Their statuses and physical appearances are unknown.
 * "Crazy Lace" (former Crystal Gem, mentioned by Bismuth)
 * "Biggs" (former Crystal Gem, mentioned by Bismuth)
 * "Snowflake" (former Crystal Gem, mentioned by Bismuth)
 * Other Amethysts (former Crystal Gems, mentioned by Bismuth)
 * Nephrite (Homeworld ship pilot, mentioned by Bismuth to Pearl)

"Beta"

 * Many Corrupted Gems are seen trapped in cages in the Beta Kindergarten. Their bodies are hidden by shadows and only their glowing yellow eyes can be seen.
 * Unknown Defective Carnelian (Mentioned by Peridot)

"Earthlings"
Another Corrupted Gem can be seen in a cage. Only its two eyes and large six-clawed hand can be seen.

"Adventures in Light Distortion"
When Steven is adjusting the Roaming Eye's form calibration system for the Crystal Gems, a small type of Gem, possibly Aquamarine, can briefly be seen on the panel, which subsequently alters the Crystal Gems' forms to be small. Also, a large type of Gem, presumably Quartz, Topaz, or Bismuth can be seen.

"That Will Be All"
A countless number of Rose Quartz gems appear bubbled in a room of Pink Diamond's Zoo.

"The Trial"
The defending Zircon states that Pink Diamond's entourage did not contain any Rose Quartzes and was instead composed of several Agates and Sapphires.

"Off Colors"
Various pieces of old statues can be seen at the beginning of the episode. One appears to be a fusion of two unknown gems, while the head of a large statue has a gemstone with the same cut as a Rose Quartz's on its forehead.

Rhodonite's components are an unknown Ruby and Pearl, while Fluorite's components are six unknown Gems.

Morganite, an unknown Gem, is mentioned by Rhodonite. She was in charge of the two halves of Rhodonite (a Pearl and a Ruby) before she replaced them after she found out that they had fused.

"Gemcation"
During Garnet's brief flashback of the Rebellion, two unknown Gem silhouettes appear fighting Pink Diamond alongside Garnet, Pearl, and Bismuth.


 * On the left of the image there is a Gem with short hair around the same height of Pearl. She appears to have a thin build. Her hair is similar to the Rutile Twins' or the prosecuting Zircon's.
 * On the right of the image there is a short Gem. She resembles one of the unknown Gems in "The Answer".

"Lars of the Stars"
A group of sixty-seven elite Citrines is mentioned by Emerald to have guarded her fastest ship, the Sun Incinerator, on the docking bay of the planet Klavius 7. Lars and the Off Colors are able to successfully sneak past all of the guards in order to steal the ship. Emerald also mentions that one of the crimes Lars and the Off Colors are accused of impersonating imperial officers in a cosmic jubilee.

"Jungle Moon"
In Stevonnie's dream, the name shown on Dr. Maheswaran (who represents Yellow Diamond in the dream)'s phone is Nephrite-XJ Cut-763. She seems to have been reluctant to begin colonizing the planet due to the presence of organic life, causing Yellow Diamond to demand her to do her job, threatening to shatter her and her crew herself otherwise. According to the silhouette on the phone, she has spiky hair.

Yellow Diamond also attempts to contact the leader of the fleet, however, Pink Diamond interrupts her, so the leader's name and appearance are never shown.

"Your Mother and Mine"
During the flashback, many Quartzes belonging to Pink Diamond appeared, emerging from their incubation in the ground alongside Rose Quartz. The silhouettes of other Quartzes, whose purple coloring suggesting they are Amethysts, are also shown working in the kindergarten. Unknown Crystal Gems also appeared in the flashback, standing alongside Rose and fighting unknown Homeworld Gems at the Ancient Sky Arena.

Near the end of the episode, Rhodonite said there will be Agates on one of Yellow Diamond's Asteroid Mines that they were heading towards.

"A Single Pale Rose"
In the scene, when Steven came back, there are many gems that witnessed Pink Diamond's shattering, including a flail wielding white gem that Garnet poofs, and a gem with a sword that Pearl fought.

Heap of Trouble
There are some unknown Gems in Heap of Trouble.

Attack the Light
There is an unknown Gem from Steven Universe: Attack the Light.

Save the Light
During a flashback to Hessonite's past, several unknown Gems are seen during the war.

Gems mentioned to be Citrines by Garnet can be heard guarding a door on Hessonite's warship, but they're not seen. The same Citrines believe the sounds they're hearing are the result of a Nephrite drill.

Steven Universe Comics
There are some unknown Gems from the Steven Universe comics.

Trivia

 * The unknown Quartz warrior in "Sworn to the Sword" is voiced by Michaela Dietz, implying she may be an Amethyst (or some other type of Quartz).
 * The Gems mentioned by Bismuth all correspond to real-life minerals. "Crazy Lace" is a variety of Agate. "Biggs" is a variety of Jasper. "Snowflake" is a type of Obsidian. "Nephrite" is one of the minerals called Jade.