When I was a kid and we had a coal furnace in the basement, I’d dig through the coal bin and find large lumps with beautiful fern and sea lily imprints and set them aside to save.
Dad, being perpetually oblivious would, without fail, toss them into the furnace while I was asleep or in school.
Shucks. we had a ‘Stoker’ -— but it still needed filling...Ah! The good ol days.....