The discovery of gold and silver in the American West during the mid-19th century came at a fortuitous time. Just as production of the precious metals began in earnest, tin and copper mining in Cornwall, England, started to decline. As one sustained mining rush ended, another began, and the renowned Cornish miners crossed the Atlantic to help it flourish. But they brought more than just their famous hard-rock mining skills; they also imported their superstitions and lore, specifically a belief in mine-dwelling fairies called Tommyknockers.

Cornish miners began immigrating to America in the 1860s and quickly earned respect at American mines. They had years of experience tunnelling and mining that Americans at the time lacked, and their seemingly uncanny ability to sniff out veins of ore made them extremely valuable to stateside mine owners.

They also popularized many of the mining terms that became part of the permanent industry lexicon, like shafts, levels, winzes, raises and adits. The creation of the miner’s code of signals, which allowed hoisters to communicate with miners below using bells, is also credited to the Cornish.

Their success often led mine owners to ask them if they knew others back home with similar experience who would be willing to immigrate for work. The typical answer was, “Well, me cousin Jack over in Cornwall wouldst come, could ye pay ‘is boat ride.” That common refrain eventually earned them the nickname Cousin Jacks.

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The origins of the Tommyknockers (also known as Knockers) vary depending on the telling, but most miners agreed they were small, dwarf-like creatures that were somewhere between one-and-a-half and two feet tall. Some believed them to be greenish in colour and outfitted in miniature miners’ clothes.

The Knockers were, according to some Cornish folklore, the spirits of miners who had died in previous cave-ins; other lore described them as the ghosts of the Jewish men who crucified Jesus Christ and were sent by the Romans to work as slaves in the mines.

However they came to be in the mines, the Tommyknockers were generally regarded by the Cousin Jacks as benevolent but mischievous little pranksters who would filch miners’ picks, candles or clothes on a lark. But they also proved useful to the miners: some said they would knock on the mineshaft walls to alert miners to a particularly rich vein of ore, the sound getting louder as the men moved closer to the vein.

Cornish miners also thought they looked out for the welfare of the mine’s employees. Just before cave-ins, Tommyknockers would knock loudly on the walls of the mine as a warning, to give the miners enough time to escape. Cousin Jacks considered the Knockers their protectors and essential to their safety while they worked.

They could become malicious, however, if neglected or offended. Whistling was thought to disturb the fairies and for that reason considered to be bad luck. Miners who spoke ill of the Knockers did so at their own risk. To keep the sprites in their good books or to say thanks for overseeing their safety, miners would leave behind pieces of their pasty from lunch for the Knockers to nibble on.

Mine owners came to accept that doing business with the Cornish meant entertaining their belief in the Knockers. That belief was so strong that in 1956, when a large California mine ended operations, miners lobbied the mine’s owners to hold off closing up the mine long enough to let the Tommyknockers make their way out, so they could go to work in other mines. The company complied.

Many of the phenomena attributed to the Tommyknockers can be easily explained by more earthly factors. Before a collapse, mine caves have a tendency to creak and groan under the weight they can no longer shoulder. And in such a poorly lit, expansive place, it is easy to misplace a tool or a piece of food, and then find it later – or not. But mines at the time were dark and dangerous places, and in such a precarious and risky occupation it is easy to understand why miners developed myths and lore. It was their collective imagination that cemented the Tommyknockers’ place in American mining culture.