The black shale Marcellus Formation stretches from much of the southern half of New York State through much of Pennsylvania and into West Virginia and Eastern Ohio.

FORBES: My Prediction Was Wrong: Why We Didn't Get To $8 Natural Gas

The entire city of Fort Worth sits over a gas dense layer of black rock called the Barnett Shale that only recently became possible to access.

NPR: Drilling for Gas in Dallas-Fort Worth

While the US has turned to shale gas, Europeans have once again embraced the black stuff, as the cost of coal has plummeted.

BBC: Green energy on the back foot after carbon trading blow