Martin Marietta Aggregates in Jefferson County, Colorado, March 2013. Photo credit: Michael O'Keeffe for the CGS.

Industrial Minerals

Industrial minerals currently mined in Colorado include quarry aggregate (crushed stone), sand, gravel, industrial gas (helium and carbon dioxide), limestone, gypsum, shale, nahcolite (sodium bicarbonate), and dimension and decorative stone. Sand, gravel, and quarry aggregate play an important part in Colorado’s infrastructure because they are used to produce concrete, asphalt, road base, and construction fill for our roads and other construction projects. Limestone is used primarily to produce cement which is also key to construction activities across the state. Gypsum (used to produce drywall or sheetrock), clay (for the production of bricks), and shale (used to construct lightweight aggregate) are also important parts of the construction industry in the state.

The CGS creates geologic maps through our STATEMAP program that, among other goals, define the locations of specific rocks that contain industrial mineral resources. These maps are used by public and private entities to locate deposits suitable for removal and processing, to determine what resources should be set aside during land-use planning, and to provide field data for future resource supply-and-demand planning and modeling. It is important to know where these resources are so these areas can then be set aside for future development. For example, if local sources of aggregate are depleted, the cost to transport this material will be passed on to local, state, and federal agencies and ultimately, the tax payer. Information from geologic maps are used to create derivative maps that rate geological units for their general potential to contain certain industrial minerals, hazards, or other geological properties. This allows non-geologists to easily determine the potential location for these properties. The CGS maintains a general mineral potential (derivative) map for the geologic quadrangles that we otherwise field map in detail.

The primary uses of sand and gravel is for concrete aggregates, road base and coverings, road stabilization, construction fill, asphaltic concrete and other bituminous mixtures, and other concrete products. Other uses include plaster and gunite sands, snow and ice control, filtration, railroad ballast, and roofing granules. Crushed stone is primarily used for construction material especially in road construction/maintenance and cement manufacturing. For a description of the geology of sand, gravel, and quarry aggregates, the CGS published ON-007-05 Colorado Aggregate Resources that shows the locations, geology, and descriptions of these natural deposits.

Colorado uses a large amount of aggregate to build and maintain infrastructure. Colorado quarry operators produced 51.81 million tons of aggregate (sand, gravel, and crushed stone) in 2018. The estimated 2018 production value was $284 million for sand and gravel and $141 million for crushed stone (see IS-82 for more information). The cost of aggregate to the user is highly dependent on aggregate transportation costs. Locating quarries close to population centers helps lower overall costs. However, residential and commercial development near an aggregate source can make permitting a new or expanding quarry a challenge.

Special Publication 5A and 5B, Sand Gravel and Quarry Aggregate Resources, Colorado Front Range Counties will assist local Front Range governments identify potential sources of sand, gravel and quarry aggregates. Digital versions of the aggregate resource maps may be found in OF-00-09 Atlas of Sand, Gravel, and Quarry Aggregate Resources, Colorado Front Range.

Portland cement in Colorado is used primarily in the production of concrete. Concrete consists of a mixture of aggregates and paste. Sand, gravel, or crushed stone is mixed with water and cement. According to the Portland Cement Association, cement is created by heating lime, silica, alumina, iron, and other materials at high temperatures which creates small round pellets called clinkers that are ground, mixed with limestone and gypsum, and used to make concrete.

The open-pit quarry supplying Upper Cretaceous Niobrara Formation limestone to the Holcim Portland Cement plant in Florence, Colorado. Photo credit: Colorado Geological Survey
The open-pit quarry supplying Upper Cretaceous Niobrara Formation limestone to the Holcim Portland Cement plant in Florence, Colorado. Photo credit: Colorado Geological Survey

In 2018, three Portland cement plants operated in Colorado. All three mining companies sourced the Upper Cretaceous Niobrara Formation as feedstock for their cement products. Like the aggregate business, the production of cement is largely tied to the construction industry. Estimated Portland cement production (e.g. shipments from Colorado) in 2018 was 2.5 million tons. Production and average cement prices are shown in our annual Mineral and Energy Activities reports.