Alchemical Coal

Alchemical Coal is an advanced fuel source, while it is not rare, it is uncommonly seen. It is not a very stable, or efficient fuel source. Its typical cost is about 60gp a ton. When encountered on the Plane of Earth, the deposits are large to medium sized, and typically occur when a coal has had to time harden and crystalize as a result of the high heat and pressures of the plane.  Even with it being a terrible fuel source, it is seen used in engines for airships, as it can be still slightly more useful than green wood or low grade coal.

Airships that use this are typically Alchemical class engines, they will not burn other fuel sources like wood or coal, these engines were purpose built for use in the engines which is why it wont accept other fuel sources. Alchemical engines are considered highly ineffective, they burn through a large amount of fuel with very little thrust gained, however they are a step up from coal and steam engines.... but not by much!

The fuel is very dangerous to store. process, and transport due to it being pretty unstable.  It is flammable and will explodes if exposed to a spark or heat source, additionally it is combustible so if it is placed under too much pressure it will ignite. It is also explosive and if in granular form in an enclosed area can detonate and ignite the atmosphere or area it currently in.