I always thought that Ceruleum=unrefined oil; crystals=coal. Basically the same thing, but in different consistencies.

I wouldn't be too surprised if ceruleum can be naturally occuring; which is why camp bluefog is so profitaple. Sure, you can refine it from crystals, but perhaps the process is too expensive/time consuming than if it were already in a liquid state. Kinda like how you can probably make fuel from coal, but the cost to do it is impractical when easier sources can be found.

Lastly, does anyone know if the aether from ceruleum disappears forever once used up? Or does it return to the environment? I always thought it was eerily similar how mako energy drains the lifestream.