On this D&D Legends and Lore, William Stark and Omar Timsah cover the lore of Gem Dragons.

Equal in power and prowess to their metallic and chromatic cousins, Gem Dragons divorce themselves from the conflict between good and evil completely. Their scales are crystalline, their powers are psionic instead of arcane, their breath weapons are not derived from the elemental energies of the inner or material plane, but from their mental command over reality itself. Theirs are the wonders of the mind, the force of will, the brilliant light of insight, and the resounding echo of discovery—but also the desiccation of despair.