Fuel mineral (4)

I believe the answer is:

coal

(Other definitions for coal that I've seen before include "Carbon fuel" , "Fossil fuel" , "Char" , "Carbonaceous rock used as fuel" , "This consists mainly of carbon" .)

I've seen this clue in the Penny Press.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.