When the world that became Loar ignited in the great cataclysm known as the Sundering, the elemancers preserved parts of the world using their magic. So intense was this magic that it altered the fundamental nature of the remnants of the world. This culminated in the formation of the worldshards, crystals found in various concentations throughout the Islands. Each of these crystals holds a portion of raw elemental power attuned to one of the four classic elements: air, water, fire, and earth.
There are also a number of other crystals that exist that scholars have yet to glean the purpose of. They are not usable by any of the elemancers in Loar.