So simply walking around Eorzea, we see plenty of fires fueled by wood, and lamps lit by oil. Some things may be powered by electricity, but I'm not sure how people would generate electricity without using living battery mages, so that's one of my questions. Ceruleum is also used to power airships and regular ships, and the trains we have are fuelled by steam engines fed with coal?
My main question is, how are the elemental crystals used as fuel in Eorzea? Is there any particular reason why traditional fuels such as oil, wood, and coal seem far more common than crystals? Do the beast tribes use those crystals exclusively for summoning, or do they also have more mundane utilities for them? How recent is the use of crystals as a fuel source?