For a long time, we've had a way to turn COAL into WOOD, but no way to turn WOOD into COAL.  Then WOOD's ability to turn into BCOL came along and I've workshopped an idea for a new hidden element:

(Hidden elements) Compressed coal (or CCOL):

CCOL is formed when BCOL is under a pressure of 180 or higher.  CCOL becomes COAL when under a pressure of 3 or lower.  This hidden element is meant to allow BCOL to become COAL under pressure without breaking saves.  CCOL has all the same flammable properties as COAL and BCOL, but is unaffected by neutrons.