Magicitism is belief in magicite, and is what makes magicite exist.
Magicite ("mage stone") is a sapphire or amethyst (or any similar-looking bluish or purplish stone) believed to be infused with a soul of a dead person (or other sentient being). It is a variety of spiritite.
The means for producing magicite have been lost, but much of it exists in the locality due to the existence of a particular magicite-oriented religion that used to thrive before the time of the College. The means of producing magicite relies on that religion’s tenets, and it is now a dead religion. This means that until someone ressurects that religion, no more magicite may be produced.
The faith of Magia held that for people who were about to die, they could sacrifice their lives by stabbing themselves with the sharpened edges of sapphires or other blue gemstones, and in doing so their soul would be transferred to the gemstone. Then, as long as the gemstone was not destroyed, their soul would live on in peace (though unable to communicate or move on their own). Any gem with such a soul in it is considered “charged”, and called soul gem; and specifically, if the soul entered the stone in peace, it is called magicite. The faith further held that any magicite generated by killing a person against their will would result in a corrupt, “black” soul gem - called violatite - which was the only type of soul gem that had been created in the time before the rise of Magia and after its fall.