In 2012, Arizona produced more than $2 billion in nonfuel mineral commodities. While Arizona leads the nation in copper production, additional minerals ranked according to value include molybdenum concentrates, sand and gravel (construction), cement (portland) and silver.

Industrial minerals found in Arizona include sand, gravel, limestone, clay, marble, gypsum, asbestos, perlite, talc, zeolites and landscape rock.

Industrial minerals mined in Arizona such as sand and gravel produced from flood plains, washes and alluvial fans are used in the construction of highways, airports, buildings, dams and bridges.

Gravel and aggregate (a combination of rocks and sand used in the manufacture of concrete) are the most common industrial minerals in Arizona. One hundred tons of sand and gravel are needed in the construction of a standard 1,600-square-foot house.

Limestone, also abundant in Arizona, is used in the manufacture of portland cement. More than 400 active mines exist in Arizona, many of them involved in quarrying industrial minerals.

Portland cement originated from the portland stone commonly used in late 18th century England. It consists of limestone mixed with bauxite, clay, sand and shale and was used to build the Eddystone Lighthouse off Cornwall, England.

As the oldest continually producing portland cement company west of the Rocky Mountains, California Portland Cement was founded in 1891 with the opening of a plant in Colton, Calif. Subsidiary plants were later established, including one in Mojave, Calif., and one in Rillito.

The California Portland Cement Co. recognized the need to expand its market into Arizona during the 1890s. However, market conditions, capital and location prevented such a move until half a century later.

Land surveys conducted by California Portland Cement near the town of Rillito in the 1920s found a sizable limestone deposit. The first cement plant in Arizona was built by the Portland Cement Co. at Rillito in 1949 at a cost of $3 million on 200 acres.

The plant, 17 miles northwest of Tucson, supplies Tucson and south Phoenix with cement acquired from the limestone deposits at Twin Peaks, also known as Picacho de Calera.

The plant was located five miles from the quarry because of the unpredictable nature of the nearby Santa Cruz River. Early transport from quarry to plant was by truck. To improve efficiency, a covered conveyor belt was built in 1972 from the crusher at the quarry site to the processing plant. The belt, nearly four miles long and 30 inches wide, could transport up to 800 tons of limestone and shale an hour. By that time three 335-foot-long kilns operated at the plant, producing 3 million barrels of cement a year.

It takes 1.56 tons of raw materials such as limestone and shale to make one ton of cement. The cement is then mixed with aggregates and water to make concrete.

Arizona quarries also produce decorative stone including flagstone, granite and marble.

Industrial minerals are the building blocks of America’s infrastructure. Supply will continue to meet a greater demand as the 21st century progresses, and Arizona will continue to play a leading role in the nation’s production of industrial minerals.

Sources: Ascarza, William. Tucson Mountains. Arcadia Publishing. Charleston, S.C. 2010; “Industrial Minerals of Southeastern Arizona.” Arizona Geology, Vol. 22, No. 2, Summer 1992; Mineral Commodity Summaries 2013. U.S. Dept. of the Interior, U.S. Geological Survey; N. Niemuth, 2008, ADMMR OFR-08-04 Arizona’s Metallic Resources – Trends and Opportunities; Peirce, H. Wesley. “Industrial Minerals and Rocks of Arizona.” FieldNotes from the State of Arizona Bureau of Geology and Mineral Technology. Vol. 10, No. 2. June 1980; Wilson, Chuck. 1991. “Quality Unsurpassed 1891-1991: A Century of California Portland Cement Company.” Franklin Press, San Bernardino, Calif.

William Ascarza is an archivist, historian and author of five books, including “Arizona-Sonora Desert Museum” and “Sentinel to the North: Exploring the Tortolita Mountain Range,” available at Antigone Books, Cat Mountain Emporium, the Arizona-Sonora Desert Museum and the Arizona Geologic Survey’s Arizona Experience Store. Email him at