Outcrops of the Cretaceous Greenhorn and Niobrara Limestones provide
most of the cement materials in Colorado. A number of plants along the
mountain front, including a completely automated and dust-free one near
Lyons, provide the major population centers with millions of tons of
cement each year.
Colorado is richly endowed with gypsum, useful in cement and plaster
manufacture and for ornamental stone and sculpture. Along the eastern
front of the mountains, gypsum occurs in the Triassic Lykins Formation;
in the Mountain Province, it is abundant in Pennsylvanian sedimentary
rocks. Particularly high-quality Pennsylvanian gypsum is quarried at the
town of Gypsum, west of Eagle.
The Colorado portion of the Paradox Basin, in the Plateau Province,
contains immense deposits of Pennsylvanian gypsum. Here, rocks near the
surface have been pushed up into sharp northwest-trending faulted
anticlines by upward movements of gypsum and salt from depths of several
thousands of feet. The soluble salt and gypsum cores of these structures
have been washed away more rapidly than the surrounding layers of
sandstone and shale, leaving depressions such as Gypsum Valley, Paradox
Valley, and Sinbad Valley, on the crests of the anticlines. Red and
yellow Triassic sandstones and shales, especially the Chinle Formation
and the Wingate Sandstone, dip away from these valleys. Exploratory
wells indicate that vast masses of salt and gypsum are present beneath
the surface, and may extend to depths greater than 10,000 feet.