Cliffworld:Skystone

Caelumite (also known as skystone) is a mineral that occurs all thorough the Cliffworld, although concentrations dense enough to be mined are very rare. The element possesses an anti-gravitational effect, which becomes significantly stronger after the refining procedures. It becomes highly unstable in this form, however, beginning to emit dangerous radiation and lose its properties. The effect is greatly reduced by putting refined elements into a hydrogen atmosphere.

Caelumite is used to improve the carrying capacity of airships, in its refined form being able to cancel out a significant amount of the ship’s weight, which allowed to build larger and better airships.