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USGS2016

Geology and mineral resources of the Southwestern and South-Central Wyoming Sagebrush Focal Area, Wyoming, and the Bear River Watershed Sagebrush Focal Area, Wyoming and Utah: Chapter E in Mineral resources of the Sagebrush Focal Areas of Idaho, Montana, Nevada, Oregon, Utah, and Wyoming

Summary The U.S. Department of the Interior has proposed to withdraw approximately 10 million acres of Federal lands from mineral entry (subject to valid existing rights) from 12 million acres of lands defined as Sagebrush Focal Areas (SFAs) in Idaho, Montana, Nevada, Oregon, Utah, and Wyoming (for further discussion on the lands involved see Scientific Investigations Report 2016–5089–A). The purpose of the proposed action is to protect the greater sage-grouse ( Centrocercus urophasianus ) and its habitat from potential adverse effects of locatable mineral exploration and mining. The U.S. Geological Survey Sagebrush Mineral-Resource Assessment (SaMiRA) project was initiated in November 2015 and supported by the Bureau of Land Management to (1) assess locatable mineral-resource potential and (2) to describe leasable and salable mineral resources for the seven SFAs and Nevada additions. This chapter summarizes the current status of locatable, leasable, and salable mineral commodities and assesses the potential of locatable minerals in the Southwestern and South-Central Wyoming and Bear River Watershed, Wyoming and Utah, SFAs.

Wyoming, Utah↗
USGS2016

Geology and mineral resources of the North-Central Idaho Sagebrush Focal Area: Chapter C in Mineral resources of the Sagebrush Focal Areas of Idaho, Montana, Nevada, Oregon, Utah, and Wyoming

Summary The U.S. Department of the Interior has proposed to withdraw approximately 10 million acres of Federal lands from mineral entry (subject to valid existing rights) from 12 million acres of lands defined as Sagebrush Focal Areas (SFAs) in Idaho, Montana, Nevada, Oregon, Utah, and Wyoming (for further discussion on the lands involved see Scientific Investigations Report 2016–5089–A). The purpose of the proposed action is to protect the greater sage-grouse ( Centrocercus urophasianus ) and its habitat from potential adverse effects of locatable mineral exploration and mining. The U.S. Geological Survey Sagebrush Mineral-Resource Assessment (SaMiRA) project was initiated in November 2015 and supported by the Bureau of Land Management to (1) assess locatable mineral-resource potential and (2) to describe leasable and salable mineral resources for the seven SFAs and Nevada additions. This chapter summarizes the current status of locatable, leasable, and salable mineral commodities and assesses the potential of locatable minerals in the North-Central Idaho SFA, which extends from east-central to south-central Idaho. The geologically complex area is composed of many different rock units that locally contain potential mineral resources.

Idaho↗
USGS1996

Resource assessment of the Bureau of Land Management's Winnemucca District and Surprise Resource Area, Northwest Nevada and Northeast California; geology and its relation to resource genesis

The U.S. Geological Survey (USGS) is a party to joint interagency Memorandum of Understandings (MOUs) with the Bureau of Land Management (BLM) and the U.S. Bureau of Mines (USBM) to coordinate resource assessments and evaluations of BLM administered lands. Resource assessments of BLM Resource Areas, that are conducted by the USGS under these MOUs, assist the BLM in meeting inventory and evaluation, resource-management planning, and other management requirements of the Federal Land Policy and Management Act of 1976 (FLPMA). This report is one of several to be generated as part of a resource assessment of BLMadministered lands in northwest Nevada and northeast California. The project area is composed of three contiguous BLM Resource Areas (RAs), totalling 13.5 million acres, in northwest Nevada and northeast California (figs. 1, 2). The SonomaGerlach and Paradise-Denio Resource Areas in northwest Nevada together comprise the BLM's Winnemucca District. The Surprise RA is located in extreme northwest Nevada and northeast California and is part of the BLM's Susanville District, which is administered by the BLM's California state office. Henceforth in this report, the project area will be referred to as the Winnemucca-Surprise Resource Assessment Area (WSRAA). Sources of geologic data used in this compilation include the state geologic maps of Nevada (Stewart and Carlson, 1978) and California (Jennings, 1977). Other regional, largerscale geologic maps of the area that were used include the 1:250,000 scale Nevada county geologic maps (Willden, 1964; Bonham, 1969; Willden and Speed, 1974; Johnson, 1977), l:125,000-scale geologic quadrangle maps (Ferguson and others, 1951, 1952; Muller and others, 1951), 1:62,500-scale geologic quadrangle maps (Gilluly, 1967; Silberling and Wallace, 1967; Wallace and others, 1969a, b) and several 1:48,000- and 1:24,000-scale geologic quadrangle maps (e.g., Erickson and Marsh, 1974 b, c; Vikre, 1985b; Theodore, 1991 a, b; 1994; Doebrich, 1994, 1995; Jones, in press a, b). The geology of the WSRAA records a complex history of Paleozoic and Mesozoic accretionary and plutonic events followed by Tertiary extensional tectonism and magmatism. This report chronologically outlines sedimentologic, magmatic, and tectonic events that shaped the geology of the WSRAA and relates these events to the genesis and distribution of the region's mineral and non-mineral resources. This is the initial report of several scheduled to be prepared on the WSRAA. Others reports include geochemistry, geophysics, hydrothermal alteration classification using Landsat Thematic Mapper imagery, assessment of metallic mineral resources, assessment of non-metallic mineral resources, and assessment of oil and gas resources.

Open-File Report↗
USGS1987

Mineral Resources of the Antelope Wilderness Study Area, Nye County, Nevada

At the request of the U.S. Bureau of land Management, 83,100 acres of the Antelope Wilderness Study Area (NV-4)60-231/241) was studied. In this report the studied area is called the 'wilderness study area', or simply the 'study area.' No identified mineral or energy resources occur within the study area. The southern part of the area has moderate mineral resource potential for undiscovered gold and silver, and the Woodruff Formation in the southern part of the area has high resource potential for undiscovered vanadium, zinc, selenium, molybdenum, and silver (fig. 1). This assessment is based on field geochemical studies in 1984 and 1985 by the U.S. Bureau of Mines and field geochemical studies and geologic mapping by the U.S. Geological Survey in 1984 and 1985. The remainder of the study area has low resource potential for undiscovered gold, silver, lead, zinc, manganese, tin, and molybdenum. The study area also has low resource potential for undiscovered oil and gas resources. The Antelope Wilderness Study Area is about midway between Tonopah and Eureka, Nev., in the northern Hot Creek Range and southern Antelope Range of central Nevada. It is accessible by unimproved dirt roads extending 20 mi (miles) north from U.S. Highway 6 and 40 mi south from U.S. Highway 50 (fig. 2). Most of the study area consists of rugged mountainous terrain having approximately 2,600 ft (feet) of relief. The mountain range is a block tilted gently to the east and bounded on both sides by normal faults that dip steeply to moderately west and have major displacements. Most of the study area is underlain by a thick sequence of Tertiary volcanic rocks that predominantly consist of silicic ash-flow tuff, the Windous Butte Formation. Paleozoic and lower Mesozoic (see geologic time chart in appendix) marine sediments occur along the southern margin of the study area, and lower Paleozoic rocks are exposed in the northeast corner. The areas of exposed Paleozoic-Mesozoic rocks along the southern margin of the study area have moderate mineral resource potential for gold and silver in sediment-hosted, disseminated, epithermal (low-temperature) gold-silver deposits (fig. 1). These rocks consist of folded and thrust-faulted, fine-grained clastic sediments and limestone and dolomite that locally have been brecciated and hydrothermally altered. The alteration (locally, strong silicification) and geochemical associations of these rocks indicate a favorable environment for such deposits. Exploration for disseminated gold deposits in the same geologic environment is currently being conducted just south of the study area. The remainder of the study area has low resource potential for epithermal gold and silver vein deposits in the Tertiary volcanic rocks. The Cenozoic sedimentary basins adjacent to the fault-bounded mountain block have moderate potential for petroleum resources; the study area itself has low potential for petroleum resources.

Bulletin↗
USGS1987

Mineral resources of the Fort Piute Wilderness Study Area, San Bernardino County, California

The Fort Piute Wilderness Study Area (CDCA-267) is in northeastern San Bernardino County, California, near the boundary between California and Nevada. Mineral surveys were requested for 31,371 acres of the Fort Piute Wilderness Study Area. In this report the area studied is referred to as "the study area". Examination of mines and prospects in the area was accomplished by the U.S. Bureau of Mines in 1981 and 1982. Field investigations of the area were carried out by the U.S. Geological Survey in 1983 and 1985. No mines or prospects, few mining claims, and no identified resources are located within the wilderness study area. Moderate and low potential for gold resources appears limited to outcrops of gneiss and granite exposed along the eastern side of the Piute Range. Available information indicates that there is no potential for energy resources, including oil and gas, uranium, or geothermal, in the study area.

California↗
USGS2006

Mining claim activity on federal land in the contiguous United States, 1976 through 2004

Statistical compilations of mining claim activity on Federal Land derived from the Bureau of Land Management's LR2000 database have been published by the U.S Geological Survey. This report updates Causey (2005) by adding statistics for an additional year of mining claim records, incorporating any corrections in older data done by BLM, adding a Public Land Survey spatial database for South Dakota, and improving correlation of the statistics to spatial databases in Washington and Nevada. The statistics compiled from the LR2000 database are counts of number of active mining claims in a section each year from 1976 to 2004 for all states within the contiguous United States. Claims are broken down by lode and placer types and a dataset is provided summarizing all claims including millsite and tunnel-site claims. One table presents data by case type, case status, and number of claims in a section. This report includes a spatial database for each state in which mining claims were recorded. A field is present in both datasets that allows the statistical data to be joined to the spatial databases so that spatial displays and analysis can be done using appropriate software. The data show how mining claim activity has changed in intensity, space, and time. Variations can be examined on a state, as well as a national level. The data are tied to a section of land, approximately 640 acres, which allows it to be used at regional, as well as local scale. It is restricted in that it only encompasses Federal land.

Arizona, Arkansas, California, Colorado, Florida, ↗
USGS1999

Digital mining claim density map for federal lands in Nevada: 1996

This report describes a digital map generated by the U.S. Geological Survey (USGS) to provide digital spatial mining claim density information for federal lands in Nevada as of March 1997. Mining claim data is earth science information deemed to be relevant to the assessment of historic, current, and future ecological, economic, and social systems. There is no paper map included in this Open-File report. In accordance with the Federal Land Policy and Management Act of 1976 (FLPMA), all unpatented mining claims, mill, and tunnel sites must be recorded at the appropriate Bureau of Land Management (BLM) State office. BLM maintains a cumulative computer listing of mining claims in the MCRS database with locations given by meridian, township, range, and section. A mining claim is considered closed when the claim is relinquished or a formal BLM decision declaring the mining claim null and void has been issued and the appeal period has expired. All other mining claims filed with BLM are considered to be open and actively held. The digital map (figure 1.) with the mining claim density database available in this report are suitable for geographic information system (GIS)-based regional assessments at a scale of 1:100,000 or smaller.

Nevada↗
USGS1981

Maps showing mineral resource potential of the Virgin Mountains Instant Study Area, Clark County, Nevada

The Virgin Mountains Instant Study Area contains about 30,000 acres (12,000 ha) in southeastern Nevada. In accordance with the Federal Land Policy and Management Act (P.L. 94-579), the U.S. Bureau of Mines examined mines, prospects, and mineralized zones, and the U.S. Geological Survey made regional geologic, geophysical, and geochemical investigations. Tungsten and sheet mica have been produced from the study area, and oil and gas lease applications have been filed on 20,300 acres (8,200 ha). Sixteen mining claims are presently held.

Nevada↗
USGS1986

Summary geochemical maps for samples of rock, stream sediment, and nonmagnetic heavy-mineral concentrate, Pyramid Roadless Area, El Dorado County, California

The Wilderness Act (Public Law 88-577, September 3, 1964) and related acts require the U.S. Geological Survey and the U.S. Bureau of Mines to survey certain areas on Federal lands to determine their mineral resource potential. Results must be made available to the public and be submitted to the President and the Congress. This report presents the results of a geochemical survey of the Pyramid Roadless Area (5203) in the Eldorado National Forest and Lake Tahoe Basin Management Unit, El Dorado County, California. This roadless area was classified as a further planning area during the Second Roadless Area Review and Evaluation (RARE II) by the U.S. Forest Service, January 1979. The Pyramid Roadless Area lies near the crest of the Sierra Nevada about 75 miles east of Sacramento, California. the area, which is adjacent to and almost encircles the Desolation Wilderness, encompasses approximately 31,400 acres in Eldorado National Forest and the Lake Tahoe Basin Management Unit in El Dorado County, California. The area is dominated by deep rugged canyons that run eastward from the Sierra Nevada crest to Lake Tahoe basin and westward toward the Sacramento Valley. Elevations range from about 5,500 feet along Big Silver Creek on the west side of the study area to 8,895 feet at Echo Peak along the southeastern side of the roadless area. Geochemical sampling was conducted during 1982. This report summarizes the results of that investigation and provides details of the geochemical evaluation used in producing the final mineral resource assessment of the study area (Armstrong and others, 1983).

California↗
USGS1996

Great Basin geoscience data base

This CD-ROM serves as the archive for 73 digital GIS data set for the Great Basin. The data sets cover Nevada, eastern California, southeastern Oregon, southern Idaho, and western Utah. Some of the data sets are incomplete for the total area. On the CD-ROM, the data are provided in three formats, a prototype Federal Data Exchange standard format, the ESRI PC ARCVIEW1 format for viewing the data, and the ESRI ARC/INFO export format. Extensive documentation is provided to describe the data, the sources, and data enhancements. The following data are provided. One group of coverages comes primarily from 1:2,000,000-scale National Atlas data and can be assembled for use as base maps. These various forms of topographic information. In addition, public land system data sets are provided from the 1:2,500,000-scale Geologic Map of the United States and 1:500,000-scale geologic maps of Nevada, Oregon, and Utah. Geochemical data from the National Uranium Resource Evaluation (NURE) program are provided for most of the Great Basin. Geophysical data are provided for most of the Great Basin, typically gridded data with a spacing of 1 km. The geophysical data sets include aeromagnetics, gravity, radiometric data, and several derivative products. The thematic data sets include geochronology, calderas, pluvial lakes, tectonic extension domains, distribution of pre-Cenozoic terranes, limonite anomalies, Landsat linear features, mineral sites, and Bureau of Land Management exploration and mining permits.

Data Series↗
USGS2005

Geochemical Analyses of Geologic Materials from Areas of Critical Environmental Concern, Clark and Nye Counties, Nevada

INTRODUCTION An assessment of known and undiscovered mineral resources of selected areas administered by the Bureau of Land Management (BLM) in Clark and Nye Counties, Nevada was conducted by the U.S. Geological Survey (USGS), Nevada Bureau of Mines and Geology (NBMG), and University of Nevada, Las Vegas (UNLV). The purpose of this work was to provide the BLM with information for use in their long-term planning process in southern Nevada so that they can make better-informed decisions. The results of the assessment are in Ludington (2006). Existing information about the areas, including geology, geophysics, geochemistry, and mineral-deposit information was compiled, and field examinations of selected areas and mineral occurrences was conducted. This information was used to determine the geologic setting, metallogenic characteristics, and mineral potential of the areas. Twenty-five Areas of Critical Environmental Concern (ACECs) were identified by BLM as the object of this study. They range from tiny (less than one km2) to large (more than 1,000 km2). The location of the study areas is shown on Figure 1. This report includes geochemical data for rock samples collected by staff of the USGS and NBMG in these ACECs and nearby areas. Samples have been analyzed from the Big Dune, Ash Meadows, Arden, Desert Tortoise Conservation Center, Coyote Springs Valley, Mormon Mesa, Virgin Mountains, Gold Butte A and B, Whitney Pockets, Rainbow Gardens, River Mountains, and Piute-Eldorado Valley ACECs.

Open-File Report↗
USGS1998

MAS/MILS Arc/Info point coverage for the western U.S. (excluding Hawaii)

The U.S. Geological Survey has two international and one regional digital database that contains information on mineral properties. This report describes the conversion of selected data from one of the international databases - MAS/MILS (Mineral Availability System/Mineral Industry Location System) - into a spatial data product. The MAS/MILS database, obtained from the U.S. Bureau of Mines (USBM) upon its closure, contains over 221,000 records of mineral properties and processing facilities throughout the world. However, the majority of the records in the database are of sites located in the western U.S. This is due to the extensive mineral activity that has occurred in the West, and the work done by mineral professionals in the Western, Alaska, and Intermountain Field Operations Centers of the USBM. The purpose of this project was to create a spatial coverage of the western U.S. containing mineral resource information. This coverage includes information for the states of Alaska, Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming. For this report, locations from MAS/MILS were converted to a point coverage using a geographic information system (GIS). All work was done using Arc/Info v. 7.0.4. There are 128,441 points in the coverage.

Alaska, Arizona, California, Colorado, Idaho, Mont↗
USGS1982

Determination of in situ state of stress at the Spent Fuel Test-Climax site, Climax Stock, Nevada Test Site

Determination of the in situ state of stress at the site of the Spent Fuel Test--Climax, using the U.S. Bureau of Mines overcore method, indicates principal stress magnitudes of 11.6 MPa, 7.1 MPa, and 2.8 MPa. The bearing and plunge of the maximum and minimum principal stress components are, respectively: N. 56? E., 29? NE; and N. 42? W., 14? NW. The vertical stress magnitude of 7.9 MPa calculated from the overcore data is significantly less than expected from overburden pressure, suggesting the stress field is influenced by local or areal geologic factors. Results from this investigation indicate (1) the stress state at the Spent Fuel Test--Climax site deviates significantly from a gravitational stress field, both in relative stress magnitudes and in orientation; (2) numerical modeling will not realistically simulate the near-field response of the Spent Fuel Test--Climax site if gravitational and (or) horizontal and vertical applied stress boundary conditions are assumed; and (3) substantial stress variations may occur spatially within the stock.

Open-File Report↗
USGS1978

Mineral resources of the Charles Sheldon wilderness study area, Humboldt and Washoe Counties, Nevada, and Lake and Harney Counties, Oregon

A mineral survey of the Charles Sheldon wilderness study area, located in Humboldt and Washoe Counties, Nevada, and Lake and Harney Counties, Oregon was conducted in 1974 and 1975 (fig. 1A, 1B, 1C). The mineral resource potential was evaluated by geological, geochemical, and geophysical studies by the U.S. Geological Survey, and by the examination of mines, prospects, and other mineralized localities by the U.S. Bureau of Mines. The investigation identified several areas of significant mineral potential within the study area which includes the Charles Sheldon Antelope Range and the Sheldon National Antelope Refuge (fig. 1B). The Virgin Valley area contains reserves of precious opal, small quantities of decorative building stone, and low-grade uranium resources. The investigation indicates that there are several areas of potential for the discovery at depth of mercury and for base and complex precious metal sulfide deposits within the study area. Reservoir temperatures, estimated from the analysis of thermal springs, suggest that the area has low-to-moderate potential for geothermal resources. The potential for oil, gas, or coal is very low.

Nevada, Oregon↗
USGS1979

Mineral resources of the Minarets Wilderness and adjacent areas, Madera and Mono counties, California

A mineral survey of the Minarets Wilderness area and adjacent areas in the central Sierra Nevada, Calif., was conducted during 1973 through 1975. The total area covers about 620 km 2 (237 sq mi) in the Sierra and Inyo National Forests, of which about 440 km 2 (170 sq mi) are within the officially designated Minarets Wilderness. The mineral resource potential was evaluated by geological, geochemical, and geophysical studies by the U.S. Geological Survey, and by examination of mineralized rocks, prospects, and mining claims by the U.S. Bureau of Mines. The results of the survey indicate that the study area has small to moderate submarginal to paramarginal resources of copper, silver, zinc, lead, iron, and tungsten and an unevaluated potential for molybdenum resources. Limestone is present, but not of commercial quantity or quality. No other industrial minerals have been recognized in quantity. Granitic rocks have potential use as decorative stone and sand and gravel could be produced from either alluvial deposits or glacial drift. However, these commodities are more accessible elsewhere at localities closer to markets. The study area has no potential for fossil fuels, and, because of the general geologic environment, the potential for nuclear fuel minerals is considered to be low. The study area has low geothermal potential, even though it is on the western edge of the Mono-Long Valley "Known Geothermal Resource Area" (KGRA). The area is underlain by metavolcanic and metasedimentary rocks that have been intruded by granitic rocks of the Sierra Nevada batholith. Pliocene volcanic rocks are present locally. With few exceptions, the known occurrences of mineralized rock are confined to the metamorphic rocks, and the exceptions appear to be confined to plutonic rocks that are older than the Late Cretaceous granitic rocks that make up the bulk of the batholithic rocks in the study area. Although no mineral production has been recorded from prospects within the study area, mines adjacent to it have produced significant amounts of gold and tungsten. Production figures are incomplete, but mines in the Mammoth mining district (fig. 1) may have produced as much as $1 million worth of gold, silver, and other metals at the then-existing prices. The Monte Cristo mine in the Mammoth district was in production during 1978.

California↗
USGS2000

Mercury bioaccumulation in fish in a region affected by historic gold mining: The South Yuba River, Deer Creek, and Bear River watersheds, California, 1999

Mercury that was used historically for gold recovery in mining areas of the Sierra Nevada continues to enter local and downstream water bodies, including the Sacramento Delta and the San Francisco Bay of northern California. Methylmercury is of particular concern because it is the most prevalent form of mercury in fish and is a potent neurotoxin that bioaccumulates at successive trophic levels within food webs. In April 1999, the U.S. Geological Survey, in cooperation with several other agencies the Forest Service (U.S. Department of Agriculture), the Bureau of Land Management, the U.S. Environmental Protection Agency, the California State Water Resources Control Board, and the Nevada County Resource Conservation District began a pilot investigation to characterize the occurrence and distribution of mercury in water, sediment, and biota in the South Yuba River, Deer Creek, and Bear River watersheds of California. Biological samples consisted of semi-aquatic and aquatic insects, amphibians, bird eggs, and fish. Fish were collected from 5 reservoirs and 14 stream sites during August through October 1999 to assess the distribution of mercury in these watersheds. Fish that were collected from reservoirs included top trophic level predators (black basses, Micropterus spp.) intermediate trophic level predators [sunfish (blue gill, Lepomis macrochirus; green sunfish, Lepomis cyanellus; and black crappie, Poxomis nigromaculatus)] and benthic omnivores (channel catfish, Ictularus punctatus). At stream sites, the species collected were upper trophic level salmonids (brown trout, Salmo trutta) and upper-to-intermediate trophic level salmonids (rainbow trout, Oncorhynchus mykiss). Boneless and skinless fillet portions from 161 fish were analyzed for total mercury; 131 samples were individual fish, and the remaining 30 fish were combined into 10 composite samples of three fish each of the same species and size class. Mercury concentrations in samples of black basses (Micropterus spp.), including largemouth, smallmouth, and spotted bass, ranged from 0.20 to 1.5 parts per million (ppm), wet basis. Mercury concentrations in sunfish ranged from less than 0.10 to 0.41 ppm (wet). Channel catfish had mercury concentrations from 0.16 to 0.75 ppm (wet). The range of mercury concentrations observed in rainbow trout was from 0.06 to 0.38 ppm (wet), and in brown trout was from 0.02 to 0.43 ppm (wet). Mercury concentrations in trout were greater than 0.3 ppm in samples from three of 14 stream sites. Mercury at elevated concentrations may pose a health risk to piscivorous wildlife and to humans who eat fish on a regular basis. Data presented in this report may be useful to local, state, and federal agencies responsible for assessing the potential risks associated with elevated levels of mercury in fish in the South Yuba River, Deer Creek, and Bear River watersheds.

California↗
USGS2005

Geochemical characterization of water, sediment, and biota affected by mercury contamination and acidic drainage from historical gold mining, Greenhorn Creek, Nevada County, California, 1999-2001

In 1999, the U.S. Geological Survey (USGS) initiated studies of mercury and methylmercury occurrence, transformation, and transport in the Bear River and Yuba River watersheds of the northwestern Sierra Nevada. Because these watersheds were affected by large-scale, historical gold extraction using mercury amalgamation beginning in the 1850s, they were selected for a pilot study of mercury transport by the USGS and other cooperating agencies. This report presents data on methylmercury (MeHg) and total mercury (THg) concentrations in water, bed sediment, invertebrates, and frogs collected at 40 stations during 1999-2001 in the Greenhorn Creek drainage, a major tributary to Bear River. Results document several mercury contamination “hot spots” that represent potential targets for ongoing and future remediation efforts at abandoned mine sites in the study area. Water-quality samples were collected one or more times at each of 29 stations. The concentrations of total mercury in 45 unfiltered water samples ranged from 0.80 to 153,000 nanograms per liter (ng/L); the median was 9.6 ng/L. Total mercury concentrations in filtered water (41 samples) ranged from less than 0.3 to 8,000 ng/L; the median was 2.7 ng/L. Concentrations of methylmercury in the unfiltered water (40 samples) ranged from less than 0.04 to 9.1 ng/L; the median was 0.07 ng/L. Methylmercury in filtered water (13 samples) ranged from less than 0.04 to 0.27 ng/L; the median was 0.04 ng/L. Acidic drainage with pH values as low as 3.4 was encountered in some of the mined areas. Elevated concentrations of aluminum, cadmium, copper, iron, manganese, nickel, and zinc were found at several stations, especially in the more acidic water samples. Total mercury concentrations in sediment were determined by laboratory and field methods. Total mercury concentrations (determined by laboratory methods) in ten samples from eight stations ranged from about 0.0044 to 12 µg/g (microgram per gram, equivalent to parts per million). Methylmercury concentrations in these samples ranged from less than 0.00011 to 0.0095 µg/g. A field panning method was used to determine the concentration of liquid elemental mercury in 22 samples from 14 stations. Measured quantities of elemental mercury recovered by panning ranged from a trace amount estimated at 100 milligrams per kilogram (equivalent to parts per million) to 45,000 milligrams per kilogram (equivalent to 4.5 per cent, by weight). In total, 194 invertebrate samples were collected at 31 stations; 78 of the samples were analyzed for concentrations of THg and MeHg and used to calculate MeHg to THg ratios. A total of 69 frog samples were collected at 19 stations, and all were analyzed only for THg. Ranges of MeHg concentrations (µg/g, wet weight) in invertebrate samples and number of samples (n) were 0.0012-0.048 for banana slugs (Arionidae, n = 27), 0.027-0.39 for dobsonflies (Corydalidae, n = 14), 0.029-0.50 for predaceous diving beetles (Dytiscidae, n = 31), 0.026-0.52 for predaceous stoneflies (Perlidae, n = 18), 0.011-1.6 for dragonflies (Odonata, n = 46), and 0.061-0.55 for water striders (Gerridae, n = 56). The ratio of MeHg to THg in invertebrates was greater than 50 percent for 74 of 78 samples. The data from this reconnaissance sampling effort have been used by land-management agencies in selecting abandoned mine sites for remediation. The Forest Service has remediated the Sailor Flat site, and the Bureau of Land Management has initiated plans to remediate the Boston Mine drainage tunnel.

California↗