Coal
Coal was a type of rock, primarily composed of carbon, which could be used as a fossil fuel. One type of coal was called anthracite.

Combined with potassium nitrate and sulfur, coal could be used as a component in gunpowder.  ()

In 1902, the coal miners of Pennsylvania striked in the anthracite strike of 1902. ()

The Vulcan explorer Mestral found employment as a coal miner following his crash landing on Earth at Carbon Creek in 1957. ()

Captain James T. Kirk and Doctor Leonard McCoy discovered in 2268 that the people of Neural, with Klingon technical assistance, had learned to use coal to forge flintlocks and sulfur to manufacture gunpowder. ()

Dr. McCoy complained in 2268, that he was "...a doctor, not a coal miner." ()

When James Kirk ordered Montgomery Scott to bring the 's speed to warp six, Scott replied he'd "pour on the coal". ()

In a 2370 holodeck simulation of the Orient Express, the train had a locomotive powered by coal. In order to increase the train's speed, Worf helped in stoking coal into the boiler. ()

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Materials
Geology