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Euclase / ユークレース

IMG 6298


First appearance Volume 1, Chapter 1
Episode 1
Status Active
Current Location Earth
Nickname Euc
Race Gem
Age Unknown (older than 2173 years)
Hardness 7.5
Family The other Gems
Occupation Secretary
Teammate Jade
Voice Actors
Japanese Mamiko Noto
English Serena Varghese

Euclase (ユークレース, Yūkurēsu) is one of the Gems who does patrol duty, secretary work, strategy planning, and other odd jobs. One of the elder gems.


Euclase has a white and blue color scheme and wears the winter or summer uniform depending on the season. They also wear standard black shoes but no gloves or socks. Their hair is cut short with blue on one side and white on the other (The colors seems to be able to switch sides). They also have thick eyebrows.


Euclase takes their job as a secretary seriously. Despite this, they are kind and caring to all of their siblings, including Phosphophyllite. They were the first to rush into action when Phos was swallowed by a giant slug that invaded the school. It seems like they know their limits and will not do anything unnecessary if it's not the best course of action. They play along with Phos' jokes and have a strong sense of responsibility.

They are shown to be quite perceptive, being one of the first to notice Phos' strange behavior after they returned from the Moon. But are also partial to reasoning over violence.

Character Profiles

Vol 2:

  • A secretary. They're good at math.

Vol. 3:

  • Secretary. Actually an all-rounder who can handle any job.

Vol. 4:

  • Secretary. Can forecast the weather with 83% accuracy.

Vol. 6:

  • Good at math. Can recite any gem's age to the day on command.

Vol. 7:

  • Likes to look for patterns in all manner of phenomena, and then swoon over them.

Vol 8:

  • A quiet intellectual. Props Jade up as a leader, but is the gem who holds all the authority.

Vol. 9:

  • Kindly and knowledgeable. Always considers what's best for everyone.

Vol. 10:

  • Conscience incarnate. Worries about all the others.


  • Euclase is introduced along with Jade at the beginning of the story.
  • Lunarians drop a giant shell onto the Gem's school. Euclase tells Phosphophyllite to investigate it as a part of their job compiling the natural history encyclopedia. As Euclase and Jade start to leave, a slug comes out of the shell and swallows Phos. Euclase reacts quickly and slices the slug but finds that their blade has melted. After the slug was dealt with, Euclase helps the other Gems recover Phos' fragments from its shell.
  • Later, Euclase drops their paper work in the pond so they ask Rutile for anti-salt resin. During this moment, they discuss recent events such as the incident with the slug in which two sunspots appeared in one day. Euclase recounts that in the 2173 years that they know, the Lunarians have only come on average once every three days. Rutile tells them the container of anti-salt resin is missing, and Red Beryl also arrives to asks if they've seen a new underwater uniform that has also gone missing. The three find Phos, who had taken both items in order to sneak underwater with Ventricosus. Though caught and denied permission to do so, Phos manages to go underwater anyway. Euclase was among the Gems who searched the ocean for Phos later that night.
  • They assist Phos in recovering and adjusting to new legs after returning from the sea.
  • They go into hibernation with most of the other Gems.
  • Euclase continues to assist Jade.
  • After Phos successfully infiltrates the Moon and returns, Euclase becomes concerned by their behavior, speculating that it is a result of Lapis' influence, or even that the one who returned may not be the Phosphophyllite that they know. Phos manages to convince nearly half of the Gems to accompany them back to the Moon, causing grief to the rest of the Gems including Euclase.
  • This action forces Kongo-sensei to reveal bits of his origin. He tells the Gems that they should seek their own paths as Phos did and no longer rely on him as he was responsible for the current situation. Euclase was the first to reach out and offer Kongo-sensei the chance to start over as an alternative to leaving him and following Phos.
  • Upon Phos's second return with Yellow Diamond and Padparadscha, Euclase appears as the violence is over. They stand over Phos's broken body, asking calmly "This is what you wanted to happen, is it?". They offer an alternative to Phos in order to make sure everyone is safe and saying that they need Phos in their future and that the route currently unfolding will place others in danger. However, before Phos can truly agree or disagree, Cairngorm stabs Phos in the face and retrieves them and the other two Gems, leaving back to the Moon.
  • After the departure, it's revealed that Euclase orchestrated and planned the defensive, using it to find Phos's weak point.
  • Upon Phos's third return, Euclase acts as almost the mediator between Phos and Sensei, and is one of the Gems who doesn't jump to attacking Phos. In fact, they are seen shocked at the sight of it. They also attempt to persuade the other Gems to repair Phos and let them speak, however, their requests are denied.
  • Euclase asks Sensei to pray for the next 220 years, slowly forgetting about Phos.
  • After Sensei revives Phos, Euclase is woken up by the noises and speaks first when arriving at the scene. This seems to make Phos hesitate long enough for Bort to attack Phos.
  • Euclase oversees the events of Padparadscha returning before allowing Red Beryl and Obsidian (who had helped reassemble Padparadscha) to go to sleep while Jade and Euclase shovel snow around the building and asks others to deal with ice floes. Euclase figures there is something more to the inability to pray, but doesn't question further and merely says it is a "tough situation".

Extra Story

During an omake (bonus chapter), four of the Gems are shown playing cards during the night. Morganite and Phos team together against Diamond and Euclase, who the former calls "Team Eyebrows". Diamond and Euclase end up winning, causing Phos to accuse Euclase of cheating and demanding that they switch teammate. Diamond partners with Bort instead and still manages to win. So instead, Euclase partners with Jade, and again still manages to win. Finally, Phos decides to partner with Kongo-sensei...



Euclase acts as an older sibling type towards Phos, showing them kindness and patience. They display a certain level of assertiveness however, which becomes more apparent after Phos's first return from the Moon. During Phos's second return, they emerge as the violence is seemingly ended to approach Phos, speaking to them directly and saying "This isn't what you wanted, was it.". However, their level of kindness and patience reveals itself to be prevalent when Phos returns the third time, this time by themselves. Euclase is one of the only ones who are willing to give Phos a chance to speak to Sensei while the other Gems are quick to shatter Phos. Even after Phos is shattered, Euclase seems to be greatly affected and in shock. They however, pick up on Phos's request to get Sensei to pray, and carry on that request after Phos's pieces are buried for 220 years.


Though it hasn't been officially mentioned, Euclase seems to be partnered with Jade as the two are constantly seen together. Their jobs also seem to compliment each other, being a secretary and speaker respectively. They have not been seen fighting together on patrol duty as other Gems have though. Euclase and Jade have one of the healthiest partnership among the Gems, respecting each other and seeming to have a mutual understanding and communication. They have not been seen belittling each other.


Euclase has a high level of respect and loyalty towards Sensei, being one of the first ones to tell Phos that they do not wish to go to the Moon and that they want to stay with Sensei. They are also the first to speak up to amend things with Sensei after he reveals his true identity, wishing to "start over" with a mutual understanding and respect.

Gem Info

  • Mineral: Silicate
  • Chemistry: BeAlSiO4(OH)
  • Color: Shade of blue, colorless, white, light green

Euclase is a beryllium aluminium hydroxide silicate mineral. It crystallizes in the monoclinic crystal system and is typically massive to fibrous as well as in slender prismatic crystals. It is related to beryl (Be3Al2Si6O18) and other beryllium minerals. It is a product of the decomposition of beryl in pegmatites.

Euclase crystals are noted for their blue color, ranging from very pale to dark blue. The mineral may also be colorless, white, or light green. Cleavage is perfect, parallel to the clinopinacoid, and this suggested to René Just Haüy the name euclase, from the Greek εὖ, easily, and κλάσις, fracture. The ready cleavage renders the crystals fragile with a tendency to chip, and thus detracts from its use for personal ornament. When cut it resembles certain kinds of beryl and topaz, from which it may be distinguished by its specific gravity (3.1). Its hardness (7.5) is similar to beryl (7.5 - 8), and a bit less than that of topaz (8).


  • Based on Ichikawa Haruko's illustration, they're most likely Jade's teammate during patrol duty, but it's not confirmed.
  • Euclase is implied to be at least 2173 years old at the beginning of the story during their talk with Rutile.
  • Their hair color will change sides at random. It is said by Jade that if the blue is in the middle that it is good luck.


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