From introduction: This report embodies the results of investigations of three gold mining districts in Josephine and Curry Counties, southwestern Oregon.

From abstract: The Jackson gas field, in Hinds and Rankin Counties, Miss., is in the eastern Gulf Coastal Plain, about 160 miles north of New Orleans and 40 miles, east of the Mississippi River at Vicksburg. The gas is produced from a Cretaceous chalk from 2,088 to 2,236 feet below sea level. Overlying the chalk is the regular sequence of Tertiary rocks found in Mississippi. On the crest of the anticline in the city of Jackson the Cockfield formation of the Claiborne group is exposed, surrounded by the Jackson formation. Some Forest Hill sand of the Vicksburg group is exposed in the northwestern part of the area described. Overlapping these formations are Pliocene and Pleistocene terrace and alluvial deposits, and the entire area is covered by a blanket of less of varying thickness.

From abstract: This report summarizes the results of a reexamination, in 1930, of the Contact mining district, in Elko County, northern Nevada. A report published as a result of a visit in 1910 summarizes the major features of the geology of the district, and the principal new data in the present paper pertain to mining development occasioned by the completion of a railroad through the camp in 1925.

From abstract: The Rosebud coal field, named from Rosebud Creek and the village of Rosebud, includes an area of about 1,050 square miles and forms a very small part of the subbituminous and lignite coal fields of eastern Montana and Wyoming and the western part of the Dakotas. It is an irregularly bounded tract lying south of the Yellowstone River in eastern Rosebud County and western Custer County and measures 50 miles from east to west and 28 miles from north to south. It adjoins the Forsyth coal field, on the west, the Ashland coal field, on the south, and the Miles City coal field, in part, on the north.

From abstract: The Richey-Lambert coal field is an area of about 900 square miles in Richland and Dawson Counties, eastern Montana, along the divide between the Missouri and Yellowstone Rivers. In this region only flat-lying continental rocks occur near the surface. About 300 feet of the Lebo shale member and about 930 feet of the coal-bearing Tongue River member of the Fort Union formation, of Eocene age, are exposed in the area. Deposits of terrace gravel at two levels in the field are tentatively correlated with the gravel on the Cypress Hills, Saskatchewan, which has been assigned to the Oligocene by the Canada Geological Survey, and with the Flaxville gravel, of upper Miocene or Pliocene age.

From abstract: This paper gives the results of a resurvey of certain areas in Montana to which renewed interest has been directed by the development recently of a market for crude phosphate rock in British Columbia, nearby.

From introduction: This report describes the mineral resources of the western part of the Arkansas coal field and considers the features of geologic structure and stratigraphy that are essential to an understanding of the nature of occurrence of the mineral resources. The area is an irregular-shaped tract of about 1,100 square miles in Scott, Sebastian, Crawford, Franklin, and Logan Counties, in west-central Arkansas.

From abstract: This report describes a rectangular area of about 2,600 square miles in Chouteau, Hill, and Liberty Counties, Mont., adjacent to the international boundary. The area is a portion of the Missouri Plateau, a section of the Great Plains province, and lies between the Highwood Mountains, Bearpaw Mountains, and Sweetgrass Hills, of north-central Montana. The southern part of the area is drained by the Missouri River and its tributary Marias River, but the northern part is drained by the Milk River. These streams are trenched in narrow valleys several hundred feet deep. The land surface between them is a rolling plain interrupted by very broad, shallow valleys that probably were eroded during the Pleistocene epoch by large streams whose courses were doubtless diverted from time to time by the continental glaciers. These valleys are now occupied only by very small creeks.

From abstract: The High Climb pegmatite, Custer County. S. Dak., belongs to the series of pegmatitic and granitic rocks that characterize the Harney Peak region of the southern Black Hills. It intrudes pre-CamInbriani metamorphic rocks consisting chiefly of quartz-mica schist. Along part of the pegmatite contact the country rock has been altered to a tourmaline-rich schist.

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.

Abstract: The Murray area includes almost the whole drainage basins of Prichard, Eagle, and Beaver Creeks and is underlain by the pre-Cambrian Belt series which is subdivided, from oldest to youngest, as follows: Prichard formation (upper and lower parts), Burke formation, Revett quartzite, St. Regis formation, Wallace formation, and Striped Peak formation. The Belt series in this area is cut by many small monzonite stocks believed to be related to the Cretaceous Idaho batholith. This report describes only the lead-zinc mines. The lead-zinc production around Murray reached its peak in 1911 and 1912 when the Monarch, Edith Murray (Pontiac or Terrible Edith), Bear Top, Paragon, Black Horse, and Silver Strike mines were active. Many of these mines have produced ore intermittently since then, and the Jack Waite mine has been very active since about 1930.

Abstract: The fluorspar deposits near Meyers Cove, Lemhi County, Idaho, are localized along three groups of shear zones: one group strikes northeast and dips steeply northwestward, another strikes northeast and dips gently northwestward, and the third strikes northwest and dips gently southwestward. The country rocks are tuffs and flows of the Casto volcanics of Permian(?) age and the Challis volcanics of late Oligocene or early Miocene age. The known deposits are in a belt about 3 miles long and 2 miles wide and crop out at altitudes between 5,100 feet and 7,200 feet above sea level. The principal vein minerals are fluorite, chalcedony, and barite. The fluorite occurs as lodes, crusts around fragments of rock, and replacements of fine breccia. The lodes range in size from veinlets to vein zones several hundred feet long and as much as 20 feet wide and contain ore that ranges in grade from 40 percent to 85 percent CaF2; the average grade is about 50 percent CaF2.

From Abstract: Niobium (columbium) and titanium occur in several minerals and rocks of the Magnet Cove and Potash Sulphur Springs areas. Niobium is in demand for use in high-temperature and noncreep steels; titanium metal is becoming an important structural material. The Magnet Cove and Potash Sulphur Springs areas are in central Arkansas between the communities of Malvern and Hot Springs. They are underlain by similar alkalic igneous complexes consisting of nepheline syenite, more basic alkalic rocks, and calcite rock or carbonatite. The igneous rocks transect sedimentary rocks of Paleozoic age and were truncated by erosion of Late Cretaceous age.

This report describes results of a field study in the Shafter mining district and conclusions presented are drawn from field studies along with office studies.

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: "This bulletin is a summary of present knowledge of the adsorbent or bleaching clays-their distribution, field and laboratory identification, physical and chemical properties, uses, quality, and value. Problems in the drying, treating with acids, and washing are discussed, and methods of testing and rating decolorizing efficiency are described."

From abstract: This report presents the results of a reconnaissance of most of the mining districts of Oregon east of the Cascade Range, with the exception of the districts in the Sumpter quadrangle. The districts described are distributed through an area roughly coincident with the Blue Mountains, which extend over much of the northeast quarter of the State.

From Abstract: Two areas and their included mineral deposits, situated in Josephine County, southwestern Oregon, are described in this report. They lie within the Klamath Mountains, a region which is made up for the most part of rugged ridges trending in various directions but which, when viewed from higher summits, resembles a dissected plateau and is known as the Klamath peneplain. Rocks of both igneous and sedimentary origin are abundant in the districts described. The marine sedimentary rocks of the areas comprise a thick series of Carboniferous strata, with some interbedded volcanic rocks, and portions of the Galice formation, of Jurassic age, and of an Upper Cretaceous formation. The rocks of fluviatile origin include Tertiary conglomerate, Pleistocene valley fill, termed the " Llano de Oro formation," and somewhat later Pleistocene gravel and alluvium, in part glacial debris. Recent gravel is found along the present streams. The igneous rocks include several varieties of greenstone of probable Paleozoic and Mesozoic age and serpentine of late Jurassic or early Cretaceous age.

From introduction: The detailed information concerning the coal deposits of the Ashland field set forth in this report has been obtained in the course of an investigation that has been conducted both as a part of the United States Geological Survey's general systematic study of western coal lands and as an aid in the administration of the public lands. With the information obtained on the location of outcrops, the number, distribution, and thickness of coal beds, the accessibility of the coal, and the thickness of the overburden, the public lands of the region are classified as to their coal value; coal-bearing lands are differentiated from noncoal-bearing lands; and the administration of the coal-land leasing law is facilitated.

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 abstract: The report is limited to the geology of lode deposits in the northwestern part of the Boise Basin which are in or near mines that were in operation at the time of visit, in 1930. Owing to the recent inactivity of the formerly rich placer (leposits, there is nothing essential regarding them to add to Lindgren's report published in 1898. The area studied is underlain by granitic rock of the Idaho batholith, which is cut by dikes of Miocene(?) age. These dikes are dacite porphyry (intruded early) ; rhyolite porphyry, granophyre porphyry, and granite porphyry (closely related in character and age) ; and several basic varieties (of which some, at least, are of relatively late origin). Diorite porphyry dikes, of undetermined age but probably older than all of those named above, are also present.

From introduction: Geologic mapping of the Carlile quadrangle, which includes one of several uranium-producing areas in northeastern Wyoming, was undertaken to provide a detailed geologic map that could be used as an aid to further exploration for uranium deposits; to study in detail the known uranium deposits to determine whether or not there are any relations among structure, stratigraphy, lithology, and uranium deposits; and to outline, insofar as possible, areas favorable for more detailed exploration for uranium.

From abstract: The Piedmont Upland in Maryland, Pennsylvania, and Delaware is about 160 miles long and at the most 50 miles wide. Rocks that underlie the province are the Baltimore gneiss of Precambrian age and quartzite, gneiss, schist, marble, phyllite, and greenstone, which make up the Glenarm series of early Paleozoic(?) age. These are intruded by granitic, gabbroic, and ultramafic igneous rocks. Most of the ultramafic rocks, originally peridotite, pyroxenite, and dunite, have been partly or completely altered to serpentine and talc; they are all designated by the general term serpentine. The bodies of serpentine are commonly elongate and conformable with the enclosing rocks.

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.