Gemcaster

From publisher blurb: Love of jewels, gems, and precious stones of every kind are common among the svirfneblin of Aventyr. Upperworlder mages that have traveled through the Underworld and lived to tell the tale speak of their spellcasters in hushed tones, claiming that they unlock the most powerful of magics through simple, if precious, jewels. Gemcasters are a prestige class designed for the Underworld of Aventyr, but are certain to be a sparkling addition to any instance of the Pathfinder Roleplaying Game.