Chalk Creek District, Chaffee County, Colorado, USAi

Regional Level Types
Chalk Creek District	Mining District
Chaffee County	County
Colorado	State
USA	Country

St. Elmo.

The mines and prospects of the Chalk Creek district are distributed chiefly in three areas: (1) Browns Creek area in the east, (2) Baldwin Gulch area, 3 1/2 miles southeast of St. Elmo, and (3) the largest and most important, a belt 1 1/2 mile to 2 miles wide and about 10 miles long that extends from the Continental Divide northeast across Chrysolite Mountain to the northeast corner of the quadrangle. Only a few of the mines were accessible in 1951, and a large part of even such extensive workings as the Mary Murphy group of mines could not be entered during the course of this investigation. The ores of the district contain gold, lead, zinc, silver, and a little copper. Lead and zinc values are nearly equal, and their total exceeds the value of gold. The Mary Murphy mine has yielded at least 75 percent of the total output from the district.

Most of the ore was mined from pyritic quartz veins in the Mount Princeton quartz monzonite, although veins in other rocks have been productive. The veins generally strike northeast and dip steeply. They range from mere stringers a fraction of an inch thick and less than 50 feet long to lodes 50 feet thick and more than a mile long, although most are separate veins 1 to 3 feet thick. Galena and sphalerite occur in variable amounts in the pyritic quartz, chiefly in streaks 1 to 12 inches wide. Some chalcopyrite generally accompanies pyrite. The gangue is chiefly white vuggy quartz, although calcite, rhodonite, rhodochrosite, barite, and fluorite occur locally.

Strongly oxidized ore and vein matter are largely confined to the veins on the west slope of Chrysolite Mountain, where complete or nearly complete oxidation extends to a depth of about 400 feet, and partial oxidation to about 900 feet. Elsewhere, veins exposed in shallow prospect pits show little or no alteration of the sulfides. As in the Monarch district, the deeper oxidized zones are above the height of glaciation. The oxidized ore is typically brown, porous limonite or limonitic quartz with variable amounts of cerussite, calamine, smithsonite, and patches or grains of galena. Free gold reportedly occurs in much of the ore.
U.S. Geological Survey Professional Paper 289

Fossils

This region is too big or complex to display the fossil list, try looking at smaller subregions.

Localities in this Region

Other Regions, Features and Areas that Intersect

References