From Abstract: "This report describes the occurrence of the mica and its physical properties among which is an unusually wide range of colors. A table is presented showing the results of power-factor measurements made by the National Bureau of Standards on 196 samples of sheet mica from 109 mica mines and 15 feldspar mines.It is concluded that more systematic planning of mica mining, for the district as a whole. would result in an average yearly production of at least 90,000 pounds of relatively clear sheet and possibly much more."

From abstract: The Cedar Creek manganese mining district is in the southwestern part of Frederick County and the northwestern part of Shenandoah County, Virginia. The manganese ore consists chiefly of the oxides pyrolusite and psilomelane, and forms replacement pockets and fracture fillings in the Oriskany sandstone and in residual sandy clay and chert derived from the New Scotland limestone. Both these formations are of Devonian age, and both form low ridges. The minable bodies have been deposited by ground water in the zone of weathering, and most of them lie above present ground-water level. The manganese-bearing formations, together with the older and younger formations exposed in Cedar Creek Valley, have been compressed into numerous folds, and at the southwestern end of the district one of these folds passes into a normal fault with a displacement of 1,000 feet or more.

Abstract: The tungsten deposits of the Nightingale district are just within the western border of Pershing County, Nev., and in the Nightingale or Truckee Range, which lies east of Winnemucca Lake. The Tertiary volcanic rocks of the district rest unconformably upon intrusive granodiorite and steeply dipping metamorphosed limestones and slates of unknown age. The tungsten deposits are of the contact-metamorphic type: The ore consists of scheelite bearing tactite, a dark silicate rock that was formed by metamorphism of limestone at the granodiorite contact. Scheelite (calcium tungstate) is the only valuable mineral. The gangue minerals are epidote, quartz, pyroxene, garnet, calcite, tremolite, molybdenite, pyrite, pyrrhotite, chalcopyrite, arsenopyrite, apatite, and sphene. The bodies of tactite are generally tabular, and they extend downward steeply, because both the limestones and the granodiorite contact dip vertically or nearly so. The largest tactite body of the district is at the Nightingale mine; it attains a maximum thickness of 60 feet and is nearly a thousand feet long, but only for part of its length is it thick enough and rich enough to be potentially minable. That it continues downward below the mine workings, which extend to a depth of 128 feet, is shown by nine drill …

From introduction: Lode and placer deposits of massive topaz rock were discovered near the old Brewer gold mine in northwestern Chesterfield County, S. C., in 1935. Preliminary tests have shown that this rock can be used in the manufacture of refractory ware and as a source of mullite, thus augmenting supplies of kyanite that have been coming from India.

From Introduction: "The present report is based on 10 weeks of field work from mid-November 1940 until late January 1941, and 4 days in May 1941. An area of 5 1/2 square miles in and about Del Puerto Canyon was mapped on a scale of 600 feet to 1 inch, and two small areas in the vicinity of the Adobe Canyon and Black Bart chromite mines were mapped on a scale of 200 feet to 1 inch."

From Introduction: "According to present knowledge, the deposits center principally, in three areas: Bonemia Basin on Yakobi Island, Mirror Harbor on Chicagof Island, and Snipe Bay on Baranof Island. This report deals only with the deposits of the most northerly area, in and near Bohemia Basin."

From Introduction: "The Mount Vernon nickel-gold deposit is 4 1/2 miles southeast of the city of Mount Vernon, Skagit County, Wash. The writers believe that the nickel was originally present in the serpentinized peridotite and that it was dissolved and redistributed by ascending hydrothermal gold-bearing solutions while the serpentine was being altered into the silica-carbonate rock."

From Introduction: "The Riddle nickel deposit is on Nickel Mountain, also called Piney Mountain, about 5 miles northwest of Riddle, Douglas Country, Oreg. (fig. 20). The deposit is an unevenly distributed surficial blanket, containing the nickel silicate garnierite, which rests upon peridotitic rocks on the western, southern, and southeastern slopes of the mountain above an elevation of 2,000 feet. It is on the Southern Pacific Railroad, and it is about 230 miles by highway south of Portland. A poorly conditioned dirt road about 5 miles long connects the town with the nickel deposit."

From Scope of Report: "During the summer of 1940, 34 days were spent in a preliminary study of the quicksilver deposits in the Steens and Pueblo Mountains. Nearly all of the quicksilver prospects were examined and mapped, and the general geology of the east flank of the mountains from north of Andrews to Denio was reconnoitered."

This report describes field work and research done in two areas of ultramafic rocks containing chromite deposits are known at the south end of Kenai Peninsula, Alaska. The Red Mountain is the other area covered in this report.

From abstract: Scheelite ore bodies occur at widely separated localities in the Sierra Nevada near Bishop, Calif. The scheelite is found in altered sedimentary rocks at or near the contact between granitic rocks and limestones that are partly changed to silicate rocks composed largely of garnet. Mineralization was closely connected with the intrusion of the granite, the latest of the varied intrusives that make up the rocks of the Sierra Nevada.

From abstract: Tin and tungsten minerals occur in pegmatites and quartz veins at Silver Hill, in secs. 23 and 24, T. 24 N., R. 43 E., 11 miles southeast of Spokane, Wash.

Abstract: The manganese deposits of the Paymaster district, in Imperial County, Calif., extend along steeply inclined normal fault fissures which cut Tertiary (?) volcanic breccia and fanglomerate. The ore deposits are in part open-space fillings composed largely of psilomelane, and in part fault breccia replaced by psilomelane, pyrolusite, and manganite. Calcite and rock fragments are the chief impurities. High-grade ore now exposed averages about 40 percent manganese, and contains much barium. About 3,000 tons of ore averaging 42 percent manganese was produced from the district by hand-sorting in 1917-18. It is estimated that nearly the same amount could be produced again, largely from present workings. In addition, a few tens of thousands of tons of milling ore, estimated to contain between 10 and 30 percent of manganese, are believed to exist in veins one to three feet wide within one or two hundred feet of the surface.

From Introduction: "Scattered throughout the Colorado Front Range, there are many small copper deposits, believed to be of pre-Cambrian age. The have been widely prospected but have produced little or no ore. In one of these, the Copper King mine, near Gold Hill, Colo., nickel was discovered in 1930, and development in the following years has exposed some 25,000 tons of ore containing from 2 to 3 percent of nickel. No other nickel deposit is known in the Front Range, but a somewhat similar deposit has been opened in Gem mine, near Canon City and about 120 miles south of Gold Hill."

This report discusses geologic work conducted in the Strayton district, California on the deposits of quicksilver and antimony.

Report describing the characteristics of manganese deposits found in White Pine County, Nevada, and geographic information about the surrounding area.

From abstract: The Blue Wing district, Lemhi County, Idaho, is not only the principal tungsten mining district in the State but it has recently become one of the leading producers of tungsten in the United States. So far only one mine in the district is productive, but other prospects are being actively developed.

Abstract: The presence of cinnabar in the Wild Horse district, in western Lander County, Nev., has been known since about 1916, but little ore was produced until 1940. In that year and early in 1941, deposits discovered in 1939 were mined to apparent exhaustion by the Wild Horse Quicksilver Mining Co., which had produced 827 flasks at the end of April 1941. The district is underlain by moderately deformed sandstone, shale, and limestone of Lower and Middle Triassic age, locally covered by remnants of a mantle of Tertiary fanglomerate, tuff, and lava. The Triassic rocks are partly silicified, and cinnabar has been found in and near silicified rock, particularly the silicified limestone at the base of -the Middle Triassic. The ore bodies so far discovered were individually small and ill-defined, and had an average tenor of less than 0.5 percent of quicksilver. Other similar ore bodies are to be expected at moderate depths, but the cost of exploration for them may, perhaps, prove excessive.

Abstract: The northern, eastern, and southern parts of the Olympic Peninsula, Wash., contain many small deposits of manganese. Most of the deposits consist of complex manganese silicates with some carbonates, although 16,275 tons of hausmannite (Mn304) ore was mined at the Crescent mine during 1924-26. About a hundred tons of silicates have been mined from various properties, mainly for experimental purposes. Future production probably will not be large, because the silicate ores are of low grade and are difficult and expensive to treat. Moreover, most of the deposits are difficult of access, and most of the ore bodies are small isolated lenses and thin tabular bodies. The deposits are mostly in red limestone or red argillite near contacts with basalt, but a few of them are in basalt.

From Introduction: "The Opalite quicksilver district includes two deposits with a considerable past production, one deposit with a small production, and one unproved prospect. These deposits are located along the circumference of a semicircular area that extends from a short distance west of McDermitt, Nev., for about 20 miles along the Oregon-Nevada State boundary. (See fig. 34). The area thus includes parts of Humboldt County, Nev., and Malheur County, Oreg.; almost the entire production has been derived from the portion in Oregon."

Abstract: The tin and copper deposits at Majuba Hill, Pershing County, Nevada are in a partly brecciated plug of Tertiary rhyolite porphyry, which is altered nearly everywhere to quartz and sericite and in some places is intensely tourmalinized. The tin mineral, cassiterite, appears to be associated with the alteration, for the single concentration of it was formed by replacement of altered breccia. Brecciated and altered rock is, however, only a general guide to potentially tin-bearing ground, and not a specific guide to ore shoots, for most of such rock appears to contain only small amounts of cassiterite, widely and unevenly distributed. The known deposit, which is exposed only underground, is at most 20 by 20 by 10 feet in size, and may contain about 12,000 pounds of metallic tin. The deposit is cut off by a normal fault, which apparently is of small displacement, and the footwall segment has not been found. The copper deposit is in the same normal fault, about 300 feet south of the earlier-formed tin deposit. From it about 4,000 tons of 12 percent copper ore was mined in 1915-18, but none has been mined since and no copper ore is now in sight.

From abstract: The Parkfield district, one of the minor California quicksilver districts, lies on the southern end of the Diablo Range, in the southeastern part of Monterey County and the westernmost tip of Kings County. (...) Two geologically similar areas, separated by 10 miles of unmineralized rocks, have been mapped. These areas contain (1) sedimentary, volcanic, and metamorphic rocks belonging to the Franciscan formation, of probable Jurassic age, (2) sedimentary rocks of Cretaceous age, (3) a few outcrops of fossiliferous strata assigned to the Temblor formation, of middle Miocene age, (4) large masses of serpentine emplaced along fault zones in post-Miocene time, (5) lenses of silica-carbonate rock formed by the alteration of the serpentine, and (6) large areas of landslide.

From introduction: The Red Bluff Bay area was examined briefly for the Geological Survey by John C. Reed and others in 1939. During the summer of 1941 the writers, with R. E. L. Rutledge, mapped this area on a scale of 1:12,000, and examined the serpentine masses in the interior during the course of reconnaissance trips into the surrounding region.

From introduction: In this study the Geological Survey and the Bureau of Mines, United States Department of the Interior, cooperated. The author prepared detailed geologic maps showing the surface topography, geology, and workings of 11 mines, and the underground workings and geology of 7 of these; the Bureau of Mines engineers directed diamond-drilling and.bulldozer-trenching. The locations of the detailed maps are shown on plate 23, an index map overprinted on a segment of the map made by Reed and Wells.