While gold is what drew the first miners to Colorado, the production of fossil fuels is by far the most valuable resource extraction done in the state today, representing four-fifths of the state's mineral output. Natural gas is the leading mineral product, taken from the ground at more than 7,000 wells across the state. The production of natural gas more than doubled between the mid-1980s and early 1990s. Rapidly falling prices for petroleum have decreased the value of its production and have made coal the state's second most valuable mineral. Oil and natural gas are produced at more than 300 fields, although the most productive are found in the northwestern part of the state.
Bituminous coal is found in beds that underlie about one-quarter of the state.
Extraction is about equally distributed between surface and subsurface mines, and Moffat and Routt counties in the northwest are the leading producers. Nearly all of the coal is used to fuel electricity-generating plants inside Colorado and in nearby states. A small amount of coal is shipped to industrial centers in Utah and Illinois. Colorado is the nation's second leading producer of molybdenum, which is added to steel as a hardener. Other minerals produced in Colorado include sand and gravel, cement, gold, silver, zinc, stone, tungsten, limestone, helium, and lead.