Piasite is the name of the ore located in the vicinity of Mt. Piasa formed from the fossilized remains of the ancient dragon Piasa. Lava burned away much of the dragon's skin, seeping into the hollow spaces inside the bones. Over thousands of years, the process eventually removed most of the dragon's organic matter save for the golden scales. The lava hardened into an igneous rock that engulfed the remains, forming a extremely rare type of ore. The magical nature of the dragon's biology, however, was retained and the potent energies remained intact inside the ore.
Raw Piasite by itself has similar proprties of ekati in that it can provide an energy source for spellcasting. In order to make use of it, one must expose it to resonating source of magic which can ignite it. Piasite will burn to provide energy in the form of heat, giving it similar properties to coal. However, what makes Piasite different is its potency and other unique magical properties. The ignited flames repel curses and hexes, and thus are very effective wards against hostile magic. The raw energy output is comparable to that of single dragon's breath giving it a variety of applications.
Piasite's other unique property is that through the use of alchemy, it can be converted into its metal form Piasium. Piasium is stronger, lighter and more flexible than steel. However, it's rarity limits its potential uses other than for very specific purposes. Piasium has been used in the construction of airships and steam engines. Very rarely has it ever been used to create individual weapons as it is not cost-effective to mass produce due to the difficulty of digging and extracting Piasite from the area. Thus, any who are lucky enough to be able to wield weapons made of Piasium are often considered the most skilled warriors in the land.