Cripple Creek Mining District, Teller County, Colorado, USAi

Regional Level Types
Cripple Creek Mining District	Mining District
Teller County	County
Colorado	State
USA	Country

The Cripple Creek district, in the southern part of the Front Range, about 20 miles (ca. 32 km) southwest of Colorado Springs, is one of the most famous gold camps in the world. It is distinctly different from the other districts of the Front Range in having ore deposits associated with an extinct volcano of Miocene age and in having had an exceedingly large output of gold-telluride ores. The chief towns are Cripple Creek and Victor.

The historic rush of prospectors to Pikes Peak in 1859 resulted in no important discoveries, and it was not until 1874 that prospecting was carried out in the Cripple Creek district. A report that H.T. Wood, while connected with the Hayden survey, had found gold near Mount Pisgah brought a number of men into the district, but no valuable deposits were found. Occasional prospecting was carried out in the district from 1880 to 1890 by Bob Womack, who found some good ore and located the El Paso claim in Poverty Gulch. In 1891, E.M. De la Vergne and F.F. Fisbee bought the El Paso claim and located the El Dorado claim. The first real "strike" however, was made by W.S. Stratton, who sampled a ledge of granite on the slope of Battle Mountain and found it to assay $380 to the ton. On July 4, 1891, he located the Independence claim, which later became one of the richest mines in the district.

The ore deposits include veins or fissure fillings, irregular bodies due to mineralization of shattered ground, and mineralized collapse breccia. Deposits of all three groups have the same general mineral composition and show no consistent change in composition down to the lowest levels exposed.

Stages of ore deposition

The ore deposits were derived from the same general source as the dikes and like them were formed in several stages. Three stages of mineralization have been recognized. It is noteworthy that although quartz, fluorspar, and pyrite belong to all stages, their appearance differs in each stage. Other minerals, if present in more than one stage, are conspicuous only in ore.

The first stage was characterized mainly by local intense corrosion of country rock and deposition of quartz and adularia and massive aggregates of dark-purple fluorspar and quartz with comparatively coarse-grained pyrite. The quartz and adularia occur both as dense masses locally called jasper and as coatings in vugs in corroded or honeycombed granite. The constituents of the quartz-adularia aggregate may have been derived from corrosion of granite and volcanic rocks at great depth, with redeposition at higher levels. The large amount of fluorine, however, represented by the dense fluorspar, and the sulfur, represented by pyrite, were most probably original constituents of the rising solutions.

Some bodies of honeycombed granite, chiefly in the Portland, Ajax, and Elkton mines, were later permeated by telluride solutions and became rich ore, but others were not reached by the tellurides and are almost barren. The veins of dense fluorspar and quartz are as much as 2 feet (ca. 61 cm) thick, but are barren except where fractured and veined by later minerals. In places, they form an apparently unconnected step-like succession of lenticular veins. Some of them are very thin but persist for considerable distances. They have rarely been noted outside the breccia area and the major shear zones in the adjacent granite.

Except that adularia is lacking, the minerals of the second stage include those of the first but differ from them somewhat in appearance. The fluorspar is usually a lighter purple, the quartz is milky to somewhat smoky, and the pyrite is fine-grained and inconspicuous. Other minerals common to this stage are dolomite or ankerite in small rounded crystals, celestine, and the tellurides.

The most common telluride is calaverite, but considerable sylvanite and krennerite are also present. The term sylvanite is frequently applied by the miners to silvery calaverite and the term calaverite to yellowish or slightly tarnished crystals, fine-grained aggregates of which may be confused with fine-grained pale-yellow pyrite. Other tellurides, which are found in small quantity, are petzite, hessite, and a silver-copper telluride. The silver-copper telluride was found in considerable quantity in the Findlay vein above level 16 of the Vindicator mine. It seems probable that much of the material called "gray copper" by the miners, but which contains as much as 2,000 ounces (ca. 76 kg) or 3,000 ounces (ca. 113 kg) of silver to the ton, may be partly or wholly silver-copper telluride. Grains or wires of free gold accompany the tellurides in places to a depth as great as 2,900 feet (ca. 884 m).

Roscoelite, the vanadium mica, is found in places as small soft drusy masses and locally adds a green coloring matter along the edges of the veins or in inclusions. A little barite and small quantities of the base-metal sulfides, principally sphalerite, galena, and tetrahedrite, have been found. The second-stage minerals occur mostly in open though narrow cracks and in vugs. In the Cresson mine, rocks with a green roscoelite stain, delicate crystals of celestine, and conspicuous amounts of sulfide are supposed to be fair indications of a nearby ore shoot, but elsewhere the same minerals have been found without leading to any ore shoot. For the most part, the solutions of the second stage merely filled or lined cavities with minerals that may have been derived by corrosion of the walls of the conduits in or below the crater. The mineral assemblage of this stage suggests a moderate to rather low temperature. Deposition of tellurides, which marked the end of the second stage, indicates the accession of primary magmatic constituents.

The third stage is represented chiefly by smoky to colorless quartz in small to large drusy crystals and by yellow druses of chalcedony. Fine-grained pyrite occurs in thin radiating needles resembling marcasite and in small drusy patches of pyritohedrons. Calcite occurs in small scalenohedrons, and locally cinnabar fills coatings on or near the pyrite. Rarely, minute grains of fluorspar are present in barren places and cannot be regarded as a likely indication of ore. Quartz of the third stage has in places replaced celestine, dolomite, and calcite.

The third stage of deposition was comparatively insignificant. It included at least one substage in which solutions were still rising from a volcanic source, but in others, the solutions may have been of superficial origin. The presence of cinnabar indicates rising solutions; the quartz, calcite, and fine-grained pyrite may be supergene but are probably also hypogene. The crusts and minute stalactites of chalcedony in vugs have evidently been deposited by meteoric water.

U.S. Geological Survey Professional Paper 223

Some aspects of the above copy from USGS Prof. Paper 223 (Lovering, 1950) are a bit dated. The Cripple Creek District is the greatest example of a class of ore deposits known as alkaline igneous rock related gold deposits. A significant amount of work has been done on this class of ore deposit in recent years. For those interested in more modern interpretations of the geology and hydrothermal evolution of Cripple Creek and other alkaline igneous rock related gold deposits, see Jensen (2003, 2007), Kelley and Ludington (2002) and Mutschler et al. (1998).

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