From The Edge Chronicles:Stormchaser

"He had destroyed the priceless stormphrax."
           You probably must be asking, "What in the world is stormphrax?" Well, it is a piece of pure lightning containing great amounts of energy. It's as light as a feather in light but in darkness, it wieghs more than a couple tons. The academics of the floating city, sanctaphrax have been secretly trying to harness its power. What this academic has just done, he smashed a valuable piece of the stormphrax, creating an odd sepia colored powder.