Obsidian / オブシディアン
IMG 6321
First Appearance: Vol. 2, Ch. 12
Status: Active
Race: Gem
Age: Unknown
Hardness: 5
Family: The other Gems
Occupation: Blacksmith
Teammate: Unknown

From Character Introduction:

  • A smith. They look too small for this work.

Obsidian (オブシディアン, Obushidian) is one of the Gems. They are a minor character who is mainly in charge of weapon production.


Obsidian has a black color scheme and wears either the winter or summer uniform depend on season. They also wear the standard black shoes but no gloves nor socks. Their hair is cut in a medium bob.


They're cheerful, energetic, and bubbly. They seem similar to Red Beryl, very dedicated to their job and will make others weapons without hesitation if requested to.


Obsidian has so far been a minor side character who hasn't had any prominent parts of their own, occasionally being seen or taking part in activities with other Gems:

  • They joined the other Gems pulling out Ventricosus' shell from the pond, collecting Phosphophyllite's fragments, and searched for Phos when they where lost in the sea.
  • They joined the winter hibernation like the other Gems.
  • Obsidian and the other Gems collected the "Shiro" parts together.

When Phosphophyllite gained new legs, Kongo-sensei asked Obsidian to bring him the lightest blade for Phos, to which they happily oblige.


Like how other Gems treated each other, it can be assumed that they have a nice relationship with their other siblings and also like and trust Sensei.

Gem Info

  • Mineral: Mineraloid
  • Chemistry: SiO2 (pure one)
  • Color: Deep black or blackish grey

Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock, in other words from lava that has cooled on the surface. It is produced when felsic lava extruded from a volcano cools rapidly with minimum crystal growth. Obsidian is hard and brittle; it therefore fractures with very sharp edges, which were used in the past in cutting and piercing tools, and it has been used experimentally as surgical scalpel blades.

Obsidian is mineral-like, but not a true mineral because as a glass it is not crystalline; in addition, its composition is too complex to comprise a single mineral. It is sometimes classified as a mineraloid. Though obsidian is usually dark in color similar to mafic rocks such as basalt, obsidian's composition is extremely felsic. Obsidian consists mainly of SiO2 (silicon dioxide), usually 70% or more. Crystalline rocks with obsidian's composition include granite and rhyolite. Because obsidian is metastable at the Earth's surface (over time the glass becomes fine-grained mineral crystals), no obsidian has been found that is older than Cretaceous age. This breakdown of obsidian is accelerated by the presence of water. Having a low water content when newly formed, typically less than 1% water by weight, obsidian becomes progressively hydrated when exposed to groundwater, forming perlite.

Pure obsidian is usually dark in appearance, though the color varies depending on the presence of impurities. Iron and magnesium typically give the obsidian a dark brown to black color. Very few samples are nearly colorless. In some stones, the inclusion of small, white, radially clustered crystals of cristobalite in the black glass produce a blotchy or snowflake pattern (snowflake obsidian). Obsidian may contain patterns of gas bubbles remaining from the lava flow, aligned along layers created as the molten rock was flowing before being cooled. These bubbles can produce interesting effects such as a golden sheen (sheen obsidian). An iridescent, rainbow-like sheen (rainbow obsidian) is caused by inclusions of magnetite nanoparticles.


  • Obsidian has historically been used as tools, including cutting or piercing tools, by various civilizations. This is reflected in the series by the fact that Obsidian is a bladesmith.
  • They're voiced by Ryo Hirohashi in the 2017 anime adaptation.


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