1. Geochemical maps showing the distribution and abundance of selected elements in heavy-mineral concentrates from ridgetop soils from the Williams Fork Roadless Area, Clear Creek, Grand, and Summit counties, Colorado Yale Public content 1985. 2002-06-01T04:00:00Z. 2002-06-01T04:00:00Z. Geological Survey (U.S.). The Survey ; For sale by Branch of Distribution. English. Public. Colorado, Clear Creek County, Grand County, and Summit County.