From introduction: The investigations on which the greater part of this report is based were carried on by E. T. Hancock, the senior author, during the summer of 1911. They were undertaken by the United States Geological Survey under a comprehensive plan for collecting information about the undeveloped fuel resources of the Western States, both as a step toward the conservation of the coal resources of the United States and as a means of supplying the demand for information concerning the many valuable coal fields of the Western States.

From abstract: The fluorspar deposits in the Northgate district, Jackson County, Colo., are among the largest in Western United States. The mines were operated intermittently during the 1920's and again during World War II, but production during these early periods of operation was not large. Mining was begun on a larger scale in 1951, and the district has assumed a prominent position among the fluorspar producers in the United States. Within the Northgate district, Precambrian metamorphic and igneous rocks crop out largely in the Medicine Bow Mountains, and later sedimentary rocks underlie North Park and fill old stream valleys in the mountains.

From abstract: The Little Cone quadrangle includes an area of about 59 square miles in eastern San Miguel County in southwestern Colorado. The quadrangle contains features characteristic of both the Colorado Plateaus physiographic province and the San Juan Mountains, and it has been affected by geologic events and processes of two different geologic environments.

From abstract: Thorium has been found since 1949 in at least 33 deposits in an area 6 miles wide and 20 miles long in the Powderhorn district, Gunnison County, Colo. The district is underlain largely by pre-Jurassic metamorphic and igneous rocks, most of which, if not all, are pre-Cambrian in age. These rocks are overlain by sandstone of the Morrison formation of Jurassic age, and by volcanic rocks of the Alboroto group and the Hinsdale formation of Miocene and of Pliocene(?) age, respectively.

From Introduction: "The recent large increase in gold production from the Alma district has greatly stimulated interest in territory immediately to the east, where many small gold-bearing veins have been discovered. Consequently, as a cooperative project of the United States Geological Survey and the State of Colorado, 7 weeks in 1938 were devoted to renaissance work to determine the origin of the placer gold and the possibilities for discovering valuable lode deposits either near the surface or at depth."

From abstract: The largest single metal-mining operation in the history of mining in Colorado has been developed at Climax, as a result of the increased use of molybdenum in the steel and other industries. Production of molybdenum at Climax was notable for a short period during the World War; it ceased from April 1919 to August 1924 but since then has shown a steady increase. In 1930 from 1,000 to 1,200 tons of ore was milled daily, using only one unit of the 2,000-ton mill. The mine has a reserve of broken ore sufficient to furnish 2,000 tons daily for 3 years and is being developed to continue to furnish this and a still further increased output as the use of the metal may warrant.

From introduction: The greatest known potential oil resource in the world occurs in the oil shale of the Green River formation, and the richest and thickest deposits occur within the area of this report. The purpose of this investigation was to obtain data on the stratigraphic distribution and areal extent of the oil-shale beds and to estimate the potential oil resources in the area.

This report studies the geology of mineral deposits in Mount Harris, Pilot Knob, Elkhead Creek, and Daton Peek quadrangles in northwestern Colorado.

The following report was prepared in cooperation with the Colorado State Geological Survey Board and the Colorado Metal Mining Fund Board. This report concerns work done partly on behalf of the U.S. Atomic Energy Commission and is published with the permission of the Commission.