Scientists just discovered an enormous lithium reservoir under Pennsylvania

Water flows from Rock Run in the Loyalsock State Forest. The park's borders lie above the Marcellus Shale formation, which is being hydrofracked to extract gas.

Scientists have discovered a vast reservoir of untapped lithium hiding in wastewater from a Pennsylvania gas fracking site. 

The wastewater, produced by the hydraulic fracturing of rocks inside the Marcellus Shale gas wells, contains enough lithium to supply up to 40% of U.S. demand, according to the new study published April 16 in the journal Scientific Reports.