As part of the natural environment, water plays a major role in man’s activities. Water problems in Colorado revolve mainly around the best use of runoff in a state whose major catchment basins are across the continental divide from her largest population centers and most fertile farm land. Groundwater, closely related to surface water distribution and movement, is a geological problem, and in Colorado as in other states many government and private geologists serve farm and industrial communities in the search for usable supplies.
CAUTION: Old mines are dangerous! They may contain water or deadly gases, or be on the verge of collapse. Keep away from abandoned prospect pits and mine shafts. WARN AND WATCH YOUR CHILDREN.
GOLD, SILVER, AND OTHER METALS
Colorado’s [placer] and [lode] sources of gold, which gave first impetus to the series of mining booms in the state, were fantastically rich. Summit and Lake Counties, for instance, each produced more than $5,000,000 in placer gold between 1859 and 1867. During the same nine-year period, more than $9,000,000 in lode gold was produced from Gregory Gulch, a tiny canyon between Central City and Black Hawk. Other districts rivalled or surpassed these figures.
Early in the game it was recognized that almost all the deposits occurred along what came to be known as the “mineral belt,” a fifty-mile-wide zone extending southwest from the Boulder region. Most of the metals mined in the state come from this belt, but there are three notable exceptions: Cripple Creek, Silver Cliff, and western Colorado vanadium and uranium districts. In the first few years of the Colorado rush, gold ores and [placer] gold were discovered only in the northeastern part of the mineral belt. Gradually the belt was found to extend further and further southwest: Tincup was discovered in 1861, Silverton in 1870, Lake City in 1871, and Telluride in 1875. Aspen, on the western edge of the belt, was not discovered until 1879, perhaps because the area was difficult of access and lacked the easily recognizable [native gold].
In the northeast part of the mineral belt, gold and other minerals occur in [veins] in Precambrian [granite] and [gneiss]. In the Leadville and Aspen areas, ores are associated with altered Paleozoic limestones. At the southwest end of the mineral belt, in the San Juan Mountains, ore veins are found near or in Tertiary volcanic rocks. [Native gold], gold-bearing compounds, and other metallic ores in these veins originated where mineral-rich solutions from deep within the earth penetrated fissures and [joints] in the surrounding rock. Regardless of the age of the host rock, almost all the ores of Colorado were deposited in the early or middle Tertiary Period, about 35 to 70 million years ago.
Gold and silver are no longer mined extensively in Colorado, although any summer Sunday will see weekend operators panning near mountain streams or trundling rock from one-man mines. The recent rise in the price of silver has encouraged many miners to reopen old shafts. The most active mines in the state today are those producing molybdenum, lead, zinc, and vanadium. (Vanadium, although a metal, usually occurs in Colorado with radioactive minerals, and so is discussed with them rather than with the metals.)
The Colorado mineral belt extends from Boulder County on the northeast to San Juan County on the southwest. Almost all of the prominent mining districts in Colorado lie along this belt. Cripple Creek and Silver Cliff, however, lie far to the east of the general trend.
Telluride Denver Colorado Springs Alamosa BOULDER Ward Gold Hill Boulder Nederland GILPIN Central City Black Hawk JEFFERSON Golden CLEAR CREEK Empire Georgetown Silver Plume Idaho Springs SUMMIT Breckenridge EAGLE PITKIN Aspen GUNNISON Tincup CHAFFEE PARK Climax Alma Como Fairplay TELLER Cripple Creek FREMONT OURAY Ouray Camp Bird Ironton SAN JUAN Silverton HINSDALE Lake City LA PLATA Durango MINERAL Creede CUSTER Silver Cliff