Other sources of information

Sand and gravel deposits of Quaternary age were attributed using 
information from Colton and Fitch (1974) and Trimble and Fitch
(1974a,b).  An overview of the aggregate industry of Colorado,
which focussed on the Denver metropolitan area, provides information
on rock formations that may be suitable for production of crushed 
stone (Schwochow, 1980).  Maps and descriptions of sources of fire 
clay (Waage,1953) and construction clay (Spence, 1980) were consulted 
to identify rock formations having potential for other industrial-
mineral use.

References cited

Colton, R. B., and Fitch, H. R., 1974, Map showing potential 
  sources of gravel and crushed-rock aggregate in the Boulder-
  Fort Collins-Greeley area, Front Range urban corridor, 
  Colorado: U. S. Geological Survey Miscellaneous Investigations 
  Series Map I-855-D, scale 1:100,000.

Green, G.N., 1992, The Digital Geologic Map of Colorado in ARC/INFO
  Format: U.S. Geological Survey Open File Report OF-92-0507.

Langer, W.H. and Knepper, D.K., Jr., 1995, Geologic Characterization
  of Natural Aggregate: U.S. Geological Survey Open File Report
  OF-95-582.

Schwochow, S. D., 1980, The effects of mineral conservation 
  legislation on Colorado's aggregate industry, in: Schwochow, S. 
  D., ed., Industrial minerals in Colorado and the Rocky Mountain 
  region, Proceedings of the Fifteenth Forum on Geology of 
  Industrial Minerals, Golden, Colo., June 3-15, 1979, Colorado 
  Geological Survey Resource Series 8, p. 29-41.

Spence, W., 1980, Clay and structural clay products in the 
  Denver area, in: Schwochow, S. D., ed., Industrial minerals in 
  Colorado and the Rocky Mountain region, Proceedings of the 
  Fifteenth Forum on Geology of Industrial Minerals, Golden, 
  Colo., June 3-15, 1979, Colorado Geological Survey Resource 
  Series 8, p. 47-50.

Trimble, D. E., and Fitch, H. R., 1974, Map showing potential 
  gravel sources and crushed-rock aggregate in the greater Denver 
  area, Front Range urban corridor, Colorado: U. S. Geological 
  Survey Miscellaneous Investigations Series Map I-856-A, scale 
  1:100,000.

Trimble, D. E., and Fitch, H. R., 1974, Map showing potential 
  gravel sources and crushed-rock aggregate in the Colorado 
  Springs-Castle Rock area, Front Range urban corridor, 
  Colorado: U. S. Geological Survey Miscellaneous Investigations 
  Series Map I-857-A, scale 1:100,000.

Tweto, Ogden, 1979, Geologic Map of Colorado: U.S.Geol. Survey, 
  Special Geologic Map.

Waage, K. M., 1953, Refractory clay deposits of south-central 
  Colorado: U. S. Geological Survey Bulletin 993, 104 p.