The Lyons area, north of Boulder, provides pink, hard, even-grained sandstone which splits readily into slabs or flagstones. These are used in the Denver-Boulder area for sidewalks and patios as well as for facing buildings. Quarries owned by the University of Colorado provide a constant supply of handsome facing material and flagstone for new university buildings, although in recent years the high cost of stone construction has limited its use on the campus.
Lyons Sandstone is quarried near Lyons, Colorado. The salmon-colored sandstone splits along surfaces defined by slight differences in size and arrangement of the sand grains. (John Chronic photo)
Most of the buildings of the University of Colorado are faced with Permian Lyons Sandstone, which is widely used for buildings and flagstones throughout the Boulder-Denver area. The University Museum, shown here, was established in 1902, and contains over a million scientific specimens, including many Colorado [fossils] and minerals. Exhibits in the Hall of Earth portray Colorado’s geologic history. (Tichnor Bros. photo)
The Lyons Sandstone was deposited as beach and bar sand along the edge of a sea which lay east of the Front Range in Permian time. After deposition, the sand was deeply buried and compacted. Now tilted up along the Front Range uplift, it comes to the surface along the east side of the range. Only between Fort Collins and Boulder does the stone have the desirable combination of hardness, thin-beddedness, and color which makes it desirable for ornamental use. The pink color of the Lyons Sandstone is derived from iron oxides, mostly [hematite], disseminated between the sand grains. Dendrites (often erroneously called [fossil] ferns or plants) ornament some slabs; they were formed by crystallization of manganese dioxide from groundwater as it slowly percolated through the rock.
Lime and Gypsum
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.