In historic mining folklore, this is a small, blue-skinned subterranean fairy or spirit that inhabits coal pits. Miners believed these entities would manifest as a blue flame or a small figure in a blue cap, offering to push heavy coal tubs in exchange for a small wage left in a dark corner. They were considered lucky and helpful, unlike other mischievous mine spirits.
Heard on the job
Leave a coin on the timber for the bluecap, or we'll be pushing these tubs ourselves.
Insider tip
The legend likely originated from the blue halo that appears over a safety lamp flame in the presence of firedamp, which early miners anthropomorphized into a spirit.