Oil Shale in the Green River Formation, Colorado, Utah, and Wyoming

Large areas of the United States are known to contain oil-shale deposits, but those areas in Colorado, Utah, and Wyoming that contain the organic-rich sedimentary rocks of the Green River Formation are of greatest promise for shale-oil production in the immediate future. Oil shale in the Green River Formation consists mostly of dolomite and contains little or no clay; therefore, it is not soft and crumbly like most shales, but is a hard, tough rock that can be cut and polished into various items of jewelry. Oil shale contains, in addition to its mineral constituents, varying amounts of solid organic matter called kerogen which, when heated in a closed retort, will convert into oil. The name Shale has been applied to the rock because many (but not all) beds of oil shale will become fissile or papery after extensive weathering, resembling the pages of an old weathered catalog. This distinctive feature results from the fact that the mineral-rich layers or laminae weather faster and deeper than the organic-rich layers.