Gemstone

A Gemstone (原石) is an esper who has gained their ability without an artificial method such as Academy City's Power Curriculum Program.

Principles
A Gemstone is an esper who gained access to their power without using an artificial method, such as the Power Curriculum Program of Academy City. Gemstones are rare and the various phenomena they create cannot be easily described; they also emit greater AIM energy amounts than an artificial esper can. It has been mentioned that the total number of Gemstones in the world is around 50.

Kamijou Touma does not belong to this group because his powers are not AIM-based. A member of the Academy City Board of Directors, Kaizumi Tsugutoshi, once had a conversation with a helper he hired from Touma's school, Kumokawa Seria, and came to the conclusion that the Imagine Breaker is not a Gemstone and is probably something beyond their current understanding.

Academy City currently has a theory that explains the Gemstones' existence: If their espers are artificial diamonds, then the Gemstones are natural ones. To further explain, the theory goes, “If a certain phenomenon has been caused artificially, then, as long as the same circumstances in the experiment are recreated in the natural world due to some factor or other, the same phenomenon will occur with no help from humans." Most people in Academy City scorn the idea of people having powers without going through the well-known power development curriculum. One exception is, who is both explicitly acknowledged and taught in school as an esper who existed before the establishment of Academy City's system. She also served as the blueprint for the creation of Academy City's first esper, the Beginning Child. It is unknown if Mifune was a Gemstone.

Gemstones are considered prized materials. Some organizations believe that by acquiring and analyzing these Gemstones, they can set the foundations for creating their own psychic power development institutions. The United States and Russia are known to have pursued power development during the Cold War and it is hinted that they have not given up on having their own power users even to this day.

Toaru Majutsu no Index Light Novel Volume SS2
On the second Friday of October, the Sisters were mobilized to rescue Gemstones which had been seized by various research organizations around the world as part of a plot by the former leader of the Stargate Project.

St. Germain Arc
For unknown reasons, members of the true Gremlin mentioned the Gemstones among the things they would have to deal with, alongside Kamijou Touma and Aleister Crowley.

World Rejecter Arc
At least one Gemstone, Tazuma Claire, was introduced as part of the Kamisato Faction. Karasuma Fran was initially believed to be a Gemstone, claiming to have become one via an implant from a UFO, but was later revealed to be a Magician posing as one.

Known Gemstones

 * Himegami Aisa
 * Sogiita Gunha
 * Gemstone Girl
 * White Player
 * Tazuma Claire