Weapons and armor made of weapon grade crystal cost the same amount to make as their masterwork counterparts. Any item could potentially be made with mundane crystal. Because mundane crystal armor is considered to be made out of metal, Druids cannot wear it.
Weapon grade crystal properly forged has 25 hit points per inch of thickness and a hardness of 8. Crystals used are chalcocite, chrysoberyl, corundrum (Sapphire), cupric sulfate, emerald, spinel, topaz, and quartz.