Strange Seas - Stranger Lands
The substance known as Cloudia (cloud-ia) is responsible for shaping not only the shape of civilization and politics of the World, but is thought to be shaping its physical appearance all the time.
Cloudia is a mineral which can be found in minute amounts almost any- and everywhere. It has the peculiar property of absolute buoyancy, to the point that in sufficient quantities it provides lift greater than its own mass, and sufficient even to completely counteract gravity.
The lifting potential of Cloudia increases with purity and concentration, as well as how energized it is. In small concentrations it takes the form of minute crystals, but if enough of it, in a sufficient purity, is brought together it naturally turns into a liquid. Further refining the liquid and adding energy, in the form of heat or electricity, will turn the Cloudia into a gas with enormous lifting potential.
While Cloudia is a mostly inert mineral it dissipates quite readily, and even in its most stable form will eventually evaporate and escape. No substance has ever proven able to contain Cloudia without loss, but Hellatite and metals alloyed with it seems to offer the best possible results.
Cloudia is found in incredibly tiny quantities in rainwater, and it is theorized that rains carry pure Cloudia from the upper Skies to the surface. The rain then deposits the Cloudia in the earth, and subsequent rains draws it deeper and deeper, and lets the Cloudia concentrate in the soil and rocks. If enough Cloudia gathers in one spot it may form a hill or even the very mountains, by minutely lifting the solids around it. The floating islands found in many places indeed have huge concentrations of crystalline Cloudia in their bedrock.