NOTE: This article contains spoilers! Read with caution.

Red Diamond
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First Appearance: Ch. 64
Status: Restoring
Race: Gem
Age: Unknown
Hardness: 10
Family: Kongo-sensei
Teammate: unknown

Red Diamond is the first of the Gems to be discovered by Kongo-sensei.


Red Diamond was the first Gem to be discovered by Kongo-sensei on the Beach where all Gems are born. At first, Red Diamond has a more crystalline appearance without proper eyes or flexible limbs. Kongo-sensei shaped them, smoothed out their features, and gave them eyes. He later also applied a skin paste because Red Diamond wanted to look more like himself. Red Diamond has a red color scheme and is depicted as wearing a white dress that resembles an oversized shirt. Their hair is cut in a medium bob.


Red Diamond is shown to be a very cheerful and curious Gem who acts like a child. They quickly developed a fondness for Kongo-sensei, who became their caretaker. When the both of them discovered the next Gem, Red Diamond asked Kongo-sensei to help them, thus leading to the creation of The School where all Gems would be housed.


In the late parts of the story, Kongo-sensei reveals bits of his past to the Gems. One day, he found that a new life form was born on the Land, and this was Red Diamond. The Gem had a crystalline body that made movement clumsy and awkward. They sensed Sensei and attempted to reach out for him but only managed to fall over. Kongo-sensei decided to take care of this Gem, protecting and teaching them. He smoothed out Red Diamond's body, fashioned eyes, clothed them, and taught them. Sometime later, the two found another Gem on the Beach, Fluorite, who was too soft to move and only twitched in place. Red Diamond asked Kongo-sensei to help them so he decided to carve out a living space from a large piece of quartz. This became the School that still stands today.

Red Diamond was taken by the Moon long before the beginning of the story. Since then, Babarat has been trying to restore them and the other Moon Gems. Red Diamond is the fastest progress among them, having already formed half of their face, much to Phos’ excitement!

Gem Info

  • Mineral: Diamond
  • Chemistry: C
  • Color: Red

Diamond (from the ancient Greek ἀδάμας – adámas, meaning "unbreakable", "proper", or "unalterable") is one of the best-known and most sought-after gemstones. Diamond is the only gem made of a single element: It is typically about 99.95 percent carbon. The other 0.05 percent can include one or more other elements which can influence its color or crystal shape. Red diamond is known to be the rarest and most expensive variety of colored diamonds. It is unknown what causes red diamond to have its red color.

It forms under high temperature and pressure conditions that exist only within a specific depth range (about 100 miles) beneath the earth’s surface. Diamond’s crystal structure is isometric, which means the carbon atoms are bonded in essentially the same way in all directions.



  • In real life, the cause of the color of red diamond is debated, though one common theory is that a deformation occurs during the formation of diamond. In the manga, Kongo-sensei states that Red Diamond's color is due to the displacement of carbon atoms adjacent to carbon and nitrogen during formation.