But Colorado and other Western states also contain significant caches of rare metals—the makings of a modern-day gold rush.
Mining companies, the federal government and state agencies are pushing to find out just how much potential new money lies beneath the dirt.
However, possible new mining in the western United States also raises environmental concerns because extracting, refining and recycling rare metals produces radioactive slurry and toxic acids.
Past mining operations left Colorado with 7,300 abandoned projects that still leak toxic waste into soil and water. Watchdog groups contend current standards must be maintained to avoid the ruinous low-cost open-pit practices that China relied on to become the world's dominant supplier.
The latest federal data indicate significant deposits of rare metals across Colorado, with identified resources topping 3 million tons at two sites in the Wet Mountains and San Juan Mountains.
Wyoming, Idaho and Alaska are the leading targets for current exploration.
Alaska's Bokan Mountain site, against a deepwater bay at the southern tip of Prince of Wales Island, likely contains some of the hardest-to-get rare earths such as dysprosium. The question that minerals analysts are asking is whether concentrations in Western host rocks are high enough to make mining profitable.
"Everybody's out looking. It's the new gold rush," said Brad Van Gosen, a Denver-based geologist for the U.S. Geological Survey, who noted that titanium deposits in Colorado rank among the nation's largest and also contain rare-earth elements.
Because 44% of Colorado land is publicly owned, with potential access to mining, Colorado Geological Survey director Matthews said the state could be overwhelmed if it is not prepared for companies rushing to stake claims.
