NOTE: This article contains spoilers! Read with caution.

Alexandrite / アレキサンドライト

IMG 6328


First appearance Vol. 3, Chapter 14
Episode 1
Status Active
Current Location Moon
Nickname Alex -chan (アレキちゃん, Areki-chan), Alex, Alexi, Lex
Race Gems
Age Unknown
Hardness 8.5
Family The other Gems
Occupation Lunarian Expert
Teammate Chrysoberyl (Former)
Voice Actors
Japanese Rie Kugimiya
English Shelby Blocker

Alexandrite (アレキサンドライト, Arekisandoraito) is one of the Gems who worked at the School as an expert on The Lunarians and is among the gems that accompanied Phosphophyllite to the moon. They do not research The Lunarians because they are interested in them, instead, they conducts the research as an attempt to overcome their condition. Alexandrite's condition is a unique one in which upon seeing a Lunarian, they are filled with anger, and turn red as a result, taking on a new personality as well. Alexandrite conducts this research in order to retain the "fresh-feeling of hatred" that they have for The Lunarians as a result of Chrysoberyl being taken from them. Kongo-sensei forbids Alexandrite from seeing the Lunarians as it causes them to go into a battle frenzy. They are one of the elder gems, however, their age is unknown.


Alexandrite, also called Alex or Alex-chan, has a blue color scheme and wears the winter or summer uniforms depending on the season. They wear the standard black shoes and sometimes black gloves, but never wear any socks. Their hair is loose and goes down to their thighs.

When they go to the moon, Alexandrite appears in their normal uniform, with the exception of a piece of cloth serving as a blindfold in order to not trigger their condition.

When their other personality takes over, their color scheme and hair becomes red.


Alex is studious, but only in terms of information and literature relating to The Lunarians. They will pester the other Gems for details regarding any fights or encounters with the Lunarians, especially if there is a new type of Lunarian. Alex is forbidden from looking or engaging with the Lunarians because doing so triggers their second personality. In this state, their hair turns red and they go into a battle frenzy that causes them to collapse afterwards before returning to their default personality.

Character Profiles

Vol 3:

  • Lunarian research maniac. Prefers to be called Alexi.

Vol 4:

  • Not just a Lunarian research enthusiast. There is a secret behind the mania.

Vol 5:

  • Has a surprising reason for becoming a Lunarian research enthusiast.

Vol 7:

  • Double Personality. Enjoys Lunarian research to the extent of forcing the hobby into the "job" category.

Vol 8:

  • Has a split personality. When partnered with Chrysoberyl they used to have a cute and gentle personality but it has been rather spoiled.

Vol. 9:

  • Split personality. Misses Chrysoberyl.


  • Blue Alexandrite collects information from the Gems that fight The Lunarians.
  • When Phosphophyllite was eaten by a slug and integrated into the shell, Alex joined the other Gems in pulling the shell out from the pond and collecting Phosphophyllite's fragments.
  • Alex joined the other Gems in searching for Phos when they were lost in the sea.
  • They joined the winter hibernation like the other Gems.
  • When Shiro, a large Moon Person creature, appeared and started chasing Diamond, they both ran past Alex who was about to take a nap. Bort and Phos then ran past Alex in the other direction but Alex corrected them. When a part of Shiro attacked Phos, they urged Alex to pick up their sword and fight back. Alex tried to refuse since they were forbidden from doing so, but finally relented given the urgency of the situation. Upon picking up the sword and looking at Shiro, Alex's berserk personality manifested and they quickly dispatched Shiro, much to the surprise of Phos. Alex also dispatched the other parts of Shiro that were fighting Bort before finally collapsing.
  • When Phos wanted to learn more about The Lunarians, Alex taught the younger Gem about the different types of Lunarians. Phos asked Alex if they liked The Lunarians, to which they said no, explaining that their investigation of The Lunarians is done in order to fix their own personality issue. They also told Phos that before the younger Gem was born, The Lunarians took Alex's partner, Chrysoberyl, away. Alex keeps The Lunarians in mind every day in order to remember the hatred they have for them.
  • They lost an original drawing of The Lunarians while recovering material from the library, and Phos helped them find it again. Along with Euclase and Jade, they noticed Phos' similarities with Lapis Lazuli.
  • Alex is convinced to go to the Moon, but must have a blindfold on their eyes so as to not be changed to Red Alex.
  • Upon learning that all abducted Gems have been ground to powder, they fall to their knees, fracturing and breaking out of shock and grief.
  • Alex remains on the Moon, learning that it is possible to remove the condition and stay permanently in one state. This happens to be the Red state, which they want, but they also want to keep someone around to control them. They choose Benitoite who is very reluctant at this. Ultimately it doesn't seem that Alex went through with this plan.
  • They bond with Barbata over food, eventually having a restaurant for the Lunarians, which is popular enough for the Lunarians to want to eat at for their "final meal".


After Phos gained their golden arms and became capable of combat, Alexandrite praised the Gem's keen observation and commented that they've changed, thinking that the prior Phos was always bragging and exaggerating everything.

Bort thinks the blue Alex is the useless one, and the red Alex is crazy as usual.

They were probably very close with their partner, Chrysoberyl, given that their capture and disappearance was the trigger for their red personality being born.

Like how other Gems treat each other, it can be assumed that Alexandrite has nice relationship with their other siblings and also likes and trusts their sensei.

Gem Info

  • Mineral: Oxide
  • Chemistry: BeAl2O4
  • Color: Bluish green in daylight, purplish red in incandescent light

Often described by gem aficionados as “emerald by day, ruby by night,” alexandrite is the very rare color-changing variety of the mineral chrysoberyl. Chrysoberyl is the third-hardest frequently encountered natural gemstone and lies at 8.5 on the hardness scale, between corundum (9) and topaz (8).

Ordinary chrysoberyl is yellowish-green and transparent to translucent. When the mineral exhibits good pale green to yellow color and is transparent, then it is used as a gemstone. The three main varieties of chrysoberyl are: ordinary yellow-to-green chrysoberyl, cat's eye or cymophane, and alexandrite.

The alexandrite variety displays a color change (alexandrite effect) dependent upon the nature of ambient lighting. Alexandrite effect is the phenomenon of an observed color change from greenish to reddish with a change in source illumination. Alexandrite results from small scale replacement of aluminium by chromium ions in the crystal structure, which causes intense absorption of light over a narrow range of wavelengths in the yellow region (580 nm) of the visible light spectrum. Because human vision is more sensitive to light in the green spectrum and the red spectrum, alexandrite appears greenish in daylight where a full spectrum of visible light is present and reddish in incandescent light which emits less green and blue spectrum. This color change is independent of any change of hue with viewing direction through the crystal that would arise from pleochroism.Alexandrite is a birthstone for June, along with pearl and moonstone. Alexandrite is also the gem for the 55th wedding anniversary.

Source: Wikipedia | GIA


"What was that...? I want it alive...! - Alexandrite, about "Shiro".

”月人のことを毎日考えて 新鮮な憎しみを 忘れないためよ”
  "I think about the Lunarians everyday so I won't forget the fresh feeling of hatred I have for them."

- Alexandrite when asked by Phos if they like the Lunarians.


  • Alex's two personalities and the accompanying color change to their hair is a reference to the fact that alexandrite in real life changes colors depending on lighting conditions.


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