Almost two centuries after California's gold rush, the United States is on the brink of a lithium rush.

Their results suggest that the Marcellus Shale “has the capacity to provide significant lithium yields for the foreseeable future” – as long as fracking continues, that is.

If scientists can extract even a conservative amount of lithium from fracking wastewater in the state, they calculate it could meet more than 30 percent of the current US demand.

That sounds really promising, but the potential environmental impact of extracting lithium from fracking wastewater is as yet unexplored, and the wastewater only exists if fracking activity continues.