Gemstone

In the Toaru Majutsu no Index series, a Gemstone (原石) is defined as an ESPer who was born with their powers. There are few of them in the world, and many aspects of their powers can't be described using scientific methods. In difference with artificially developed espers, Gemstones emit larger amounts of AIM from their bodies. It has been mentioned that the total number of Gemstones of the world is around fifty.

Kamijou Touma doesn't 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 Kamijou Touma's school (Kumokawa Seria (雲川芹亞)), and came to the conclusion that the Imagine Breaker is not a Gemstone and is probably something beyond their understanding.

Academy City currently has a theory that explains the Gemstones' existence: if Academy City's 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 of the people in Academy City scorn the idea of people having powers without going through the well-known power development curriculum.

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. USA and Russia have been known to have pursued power development during the Cold War, and it's hinted that they haven't given up on having their own power users even to this day.

Known Gemstones

 * Himegami Aisa
 * Sogiita Gunha
 * Gemstone Girl