While Southern Arizona is known for its porphyry copper deposits, Northern Arizona is better known for its nonmetallic commodities, including basalt, helium, potash and carbon dioxide (CO2).
More than 600 cinder cones comprise the 1,800-square-mile San Francisco Volcano Field and its south-central edge of Flagstaff in Coconino County.
Created by strombolian (low-level) eruptions over the past 6 million years, the San Francisco Volcanic Field includes Sunset Crater, the state’s youngest volcano and most recent example of an eruption that occurred 1,000 years ago.
The area is known for its commercial production of scoria, a volcanic rock composed of basalt and andesite. These fine-grained, dark-colored, igneous rocks make up the cinder cones, which average 1,000 feet in height and a half-mile in diameter at the base.
The Atchison, Topeka & Santa Fe Railway Co. quarried and stockpiled basalt at Winona for use in railroad ballast, concrete aggregate and cinder block. Sheep Hill, a large volcanic cone on the east side of Flagstaff, hosts a cinder pit mining operation clearly defined by the impacted disturbance on its western flank. Its colorful striations dominate the landscape, and its product is used to provide traction on winter roads and as a decorative landscape material.
Helium, a light inert gas, has many uses, including as an inert shield for arc welding and for pressuring rockets and missiles. Located in the Holbrook Basin and the Four Corners area, concentrations of helium vary from trace amounts to up to 10 percent.
Commercial concentrations average above 0.3 percent. As the first commercially produced gas in Arizona, notable helium fields include Pinta Dome, 35 miles northeast of Holbrook, and the nearby Navajo Springs and East Navajo Springs fields.
The Teec Nos Pos oil and gas field also produced helium in 1968. Today’s declining federal helium reserves may bring about renewed exploration and development of helium in Northeastern Arizona.
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