Coal can apparently form after "only" many thousands of years, but most of today's mined coal seems to come from the Carboniferous (290-360 Million years ago) a

Coal can apparently form after "only" many thousands of years, but most of today's mined coal seems to come from the Carboniferous (290-360 Million years ago) and the Cretaceous period (69-144 Million years ago).[0] [0]https://energyeducation.ca/encyclopedia/Coal_formation https://energyeducation.ca/encyclopedia/Coal_formation