He built his first prototype in 1993, buying shale from an abandoned mine to experiment with.

NPR: Squeezing Oil Out of Stones in the Rocky Mountains

Contaminated water from an abandoned mine in mid Cornwall could spill into a nearby river if levels continue to rise, says the Environment Agency.

BBC: Concern contaminated Wheal Jane water may pollute river

The writer visited an abandoned mine to study bats with Hicks.

NEWYORKER: The Sixth Extinction?

In October 2000 the floor of a 72-acre wastewater reservoir built above an abandoned mine in Kentucky collapsed, sending black sludge through the mine and out into a tributary of the Big Sandy River.

FORBES: Companies, People, Ideas

Mr. Friedland, who spent much of the 1970s traveling in India, where he studied Sanskrit, Hindu culture and Buddhism, once said he became interested in mining after stumbling upon an abandoned gold mine on property he was developing for a timber venture with Mr. Jobs, whom he met at Reed College in Portland, Ore.

WSJ: A Battle for Mongolia's Copper Lode