oil shale

plural oil shales

1. uncountableusuallyA sedimentary rock containing kerogen from which petroleum-like shale oil can be produced by pyrolysis, hydrogenation, or thermal dissolution.

   Up in the mountains along both sides of Parachute Creek the Exxon Corporation and other companies have begun to pour billions of dollars into two huge projects to turn the nation's immense reserves of oil shale into shale oil.

   1981 November 6, Robert D. Hershey Jr, “Shale Oil Is Coming Of Age”, in The New York Times, →ISSN

   1 more example

   Can you imagine squeezing oil from rock? Oil shale is different from the shale gas that is extracted through fracking. It is geologically un-evolved oil: the remnants of organic matter buried underground for millions of years but never sunk deep enough, nor long enough, to be transformed into petroleum.

   2014 April 16, Martin Lukacs, “Canada becoming launch-pad of a global tar sands and oil shale frenzy”, in The Guardian

   Synonyms: kerogen shale