Quote from: trainman203 on February 19, 2024, 05:14:59 PMThey used to sometimes call coal "diamonds." I haven't heard it or seen it in a long time, but steam firemen were sometimes called diamond shovelers or something like that. Plus there was the term blue diamond that I think sometimes meant coal. Someone from the coal regions like Jeffrey Ward will have to elucidate on that.
The term is black diamonds, and comes from the fact that both coal and diamonds are forms of carbon. Lehigh Valley, one of the bog carriers of Anthracite (clean) coal named its premier passenger train the "Black Diamond." Geologically speaking, it takes intense heat and pressure to turn carbon into diamonds. Even though Pennsylvania is home to areas where such heat and pressure literally turned rock plastic and deformed it into spectacularly bent rock formations, in those areas most of the coal deposits burned off in the process long before they could become diamonds. What didn't burn off in those regions became Anthracite or hard coal. Those places subject to less extreme folding are underlaid with multiple layers of bituminous (soft) coal deposits. So I wonder exactly what conditions coal would have to be subject to in order to turn into diamonds. Apparently those conditions didn't exist here.