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Minerals & deposits

Find USGS publications on mineral resources and deposits. Search commodities and geographic names, then check source reports for geology and assessment methods.

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USGS2019

Mineral resource of the month: Garnet

Garnet is the general name given to a group of complex silicate minerals, all with isometric crystal structure and similar properties and chemical composition. The most common garnet minerals are classified into three groups: the aluminum-garnet group, the chromium-garnet group and the iron-garnet group. Worldwide, garnet resources are large and occur in a wide variety of rocks, principally in metamorphic rocks such as gneisses and schists. Garnet also occurs in veins, contact metamorphic rocks, metamorphosed crystalline limestones, pegmatites and serpentinites. In addition, alluvial garnet sands are associated with heavy-mineral sand and gravel deposits in many parts of the world.

EARTHCARE: Global Protection of Natural Areas.↗

USGS2019

USGS critical minerals review

The United States’ supply of critical minerals has been a concern and a source of potential strategic vulnerabilities for U.S. economic and national security interests for decades (for example, see Strategic and Critical Minerals Stockpiling Act, 1939). More recently, with the rapid increase in the types of materials being used in advanced technologies (Fortier et al. 2018a), and geopolitical events surrounding the supply of rare earth elements (Ting and Seaman, 2013), among other developments, the critical minerals issue has again achieved a high level of visibility within the U.S. government (Executive Order 13817 (2017)).

Mining Engineering↗

USGS1981

Hard mineral resources around the U.S continental margin

The territorial waters surrounding the United States contain vast quantities of hard mineral resources. Some, such as sand and gravel in the New York Bight, Beaufort Sea, portions of southern California, and submerged lands near Hawaii are relatively well known and characterized by local need and immediate mining potential with available technology. Commoditie of interest to industry and having nearterm economic potential that might require new or innovative technology, inlcude phosphorites such as those in the south eastern Atlantic margin, and manganese nodules on the Blake Plateau (which have potential for catalyst material, manganese, cobalt, nickel, and platinum). Commodities having significant potential, but which are poorly known and which may require innovative recovery technology, include chrome, gold, platinum, and tin placer deposits, with special emphasis on the continental margins of northern California, Oregon, Washington, and Alaska; rock salt and evaporite minerals in the Gulf of Mexico and Atlantic; titanium and other heavy minerals in the Atlantic continental margin, and calcium carbonate. A. U.S. Department of the Interior moratorium on offshore leasing in federal waters has existed since 1968. Leasing and regulatory systems will be required to begin commercial mining or intensive exploration of the above resources

Conference Paper↗

USGS2019

Links between tectonics, magmatism, and mineralization in the formation of Late Cretaceous porphyry systems in the Yukon-Tanana upland, eastern Alaska, USA

Cretaceous-Paleocene porphyry Cu(±Mo±Au) occurrences are scattered throughout the Yukon-Tanana upland in eastern Alaska. Known occurrences in eastern Alaska are poorly characterized, despite a resurgence in exploration. Porphyry deposits in the upland are emplaced into structurally complex metamorphic rocks representing a variety of tectonic environments, resulting in diverse alteration and mineralization assemblages. New mapping, drill core logging, petrography, geochemistry, geochronology, and structural analysis allow improved characterization of the parameters of porphyry systems and identify key linkages to regional tectonic and magmatic events. New sericite 40 Ar/ 39 Ar and zircon U/Pb dates constrain porphyry systems to the Late Cretaceous-earliest Paleocene (ca. 71-63 Ma). Zircon Hf-isotope ratios and Ce and Eu concentrations indicate that Late Cretaceous-Paleocene intrusions emplaced into basement dominated by Triassic and Jurassic plutons are more isotopically juvenile, reflecting more oxidized conditions. In contrast, those emplaced into basement dominated by mid-Cretaceous plutons are more reduced crustal geochemical-affinity. Diversity in mineral assemblages in contrasting systems may reflect emplacement into crustal domains of varying compositions and oxidation states. Those formed within a domain containing more-oxidized Triassic and Jurassic plutons are molybdenite-rich and apparently lack gold. In contrast, systems formed within domains dominated by more reduced mid-Cretaceous plutons contain lower-sulfidation state mineral assemblages with reported gold.

Alaska, Yukon↗

USGS2018

USGS critical minerals review

Mining Engineering↗

USGS2021

USGS 2020 critical minerals review

Concerns about the lack of domestic production and availability of essential mineral raw materials were a recurring theme throughout the 20th century, particularly in the periods around armed conflicts (Congressional Research Service, 2019). These concerns resulted in the designation of particular minerals as “strategic” or “critical,” terms that commonly depend on the perspective of the user, but which are generally understood to relate to mineral commodities with uses in essential applications, and which are exposed to risk of supply disruptions, with attendant implications for economic and national security interests.

Mining Engineering↗

USGS1974

Relation of mineralization to calderas in the San Juan volcanic field, southwestern Colorado

A review of the calderas in the San Juan volcanic field, southwestern Colorado, indicates that lead, zinc, copper, gold, and silver mineralization took place in and near calderas which had complex histories of postsubsidence intrusive and extrusive igneous activity. Most known ore occurs in veins that follow fractures formed during the different caldera cycles, but some intrusive bodies were extensively mineralized and possibly may host disseminated, porphyry-type deposits. The mineral deposits seem to be related most commonly to the youngest and most highly differentiated late intrusives of a caldera cycle.

Colorado↗

USGS2025

Ages and trace element fertility of porphyry-related mineralization in the Philipsburg polymetallic district, Montana, with a comparison to Butte

The Philipsburg mining district is a Mo-Cu porphyry system with associated Cordilleran polymetallic veins. Geochronology was employed to date the porphyry (~66 Ma, U/Pb in zircon) and molybdenite mineralization from the veins (~76 Ma, Re-Os). Age results suggest that the two-mineralization events model proposed by Lund et al. (2018) for the Butte district can be applied to the Philipsburg deposit. Furthermore, common fertility indicators from zircon trace elements were analyzed with variable success to characterize the existing Mo-Cu mineralization of the Philipsburg porphyry. This raises concerns about the benefits of this method and/or the importance of sampling, which could impact exploration for similar porphyry deposits.

Montana↗

USGS2025

Petrogenesis and mineralization potential of the Bradley Peak komatiitic basalts, Wyoming Province

The ca. 2.72 Ga Bradley Peak greenstone terrane in the Wyoming Province contains spinifex- and cumulate-textured komatiitic volcanic rocks that may host Ni-Cu-PGE sulfide mineralization. New whole rock geochemistry classifies these rocks as Al-undepleted komatiitic basalts derived from a parental melt with ~17 wt. % MgO. Isotopic data (Sm-Nd, Re-Os) and REE profiles suggest a plume source and possible assimilation of juvenile footwall volcanic rocks. Calculated sulfur concentrations at sulfide saturation and low-detection PGE geochemistry indicate these magmas did not saturate a sulfide liquid resulting in sulfide mineralization. Although the Bradley Peak komatiitic basalt flows are unlikely to host magmatic sulfide mineralization, they are likely the source of Au for regional orogenic gold deposits.

Wyoming↗

USGS2025

Deformation mechanisms in quartz veins and shear zones elucidate the origin of gold mineralization at Pogo, Alaska

Pogo is a quartz vein hosted, ca. 8 Moz gold deposit. Although it has similarities to orogenic and magmatic-hydrothermal deposits, its origin remains enigmatic. Observations from surface exposures, underground workings, and drill core provide new constraints on quartz vein origins with implications for mineralization. Abundant, largely barren metamorphic segregation quartz veins are found throughout interior Alaska and share characteristics with mineralized quartz veins at Pogo. Pogo quartz veins show crystal plastic deformation fabrics consistent with greenschist to amphibolite facies metamorphism and a lack of internal shear. In contrast, gold in Pogo quartz veins occurs in brittle microfaults and fractures with sulphides such as arsenopyrite and pyrrhotite. Major and minor cataclastic shear zones also exist at Pogo. Cataclastic shear zones commonly cut the mineralized quartz veins and porphyroclasts are dominated by quartz with the same plastic deformation fabrics found in the major Pogo quartz veins. The porphyroclasts, and the carbonaceous clay-rich matrix they sit in, also contain gold indicating that the shear zones postdate quartz and earliest gold deposition. These observations suggest that competency contrasts between the quartz veins and their phyllosilicate-rich host rocks controlled transient permeability formed by late, preferential brittle deformation events localizing sulphide ± gold deposition.

Alaska↗

USGS2025

The influence of nodule versus crust morphology on the composition of seamount-hosted ferromanganese minerals

Ferromanganese mineral precipitation in the global oceans is ubiquitous, occurring in the form of both crusts and nodules at a broad range of depths and seafloor terrains. Although ferromanganese crusts and nodules are both composed of ferromanganese minerals, mineralogy and mean element concentrations compiled for regional crust versus nodule occurrences differ. Notably, most published compilations compare nodules from abyssal plain sediments to crusts forming on seamounts, and do not address the question as to whether mineral morphology may affect the composition of crusts and nodules in addition to environmental factors. To address this, we have compiled a dataset of co-located hydrogenetic (seawater sourced) open-ocean ferromanganese crusts and seamount-hosted nodules. The preliminary data presented here support our hypothesis that co-located crusts and nodules exhibit similar compositions, both in terms of their mineralogy and mean element concentrations, as well as overall variance in concentrations for any given element. These data indicate that local processes influence sample-to-sample variation in both crusts and nodules, in contrast to broader ferromanganese variation reported between open-ocean seamounts- hosted crusts and abyssal plain-hosted nodules.

Conference Paper↗

USGS2025

Niobium-rich minerals from the Sheep Creek carbonatite-related deposits, Montana, USA

The Sheep Creek area in southwest Montana contains a number of small, tabular, carbonatite-related deposits that are rich in Nb- and REE-minerals. Two of the “vein-dikes” were mined at a small scale for Nb in the late 1950s. The most abundant Nb-bearing minerals are columbite-(Fe), nioboaeschynite-(Ce), baotite, and two varieties of Ti-Nb-Fe-oxide. An early oxide with Ti/Nb (atomic) near unity later broke down to a mixture of columbite + TiO2 with distinctly lower Nb content. Zircon intergrown with the Nb-REE minerals was dated by U-Pb methods to 116±2 Ma. This age is in agreement with previous dating (Th-Pb on monazite, Re-Os on molybdenite), and indicates that the Sheep Creek deposits are early Cretaceous in age.

Montana↗

USGS1987

Molecular orbital (SCF-Xα-SW) theory of metal-metal charge transfer processes in minerals

A number of mixed valence iron oxides and silicates (e.g., magnetite, ilvaite) exhibit thermally induced electron delocalization between adjacent Fe 2+ and Fe 3+ ions and optically induced electronic transitions which are assigned to Fe 2+ →Fe 3+ intervalence charge transfer. In this paper, the mechanism of electron delocalization (i.e., polarons versus itinerant electrons) and the nature of optically induced intervalence charge-transfer in minerals are investigated using molecular orbital theory. SCF-Xα-SW molecular orbital calculations were done for several mixed-valence (Fe 2 O 10 ) 15− clusters corresponding to edgesharing Fe 2+ and Fe 3+ coordination polyhedra. A spinunrestricted formalism was used so that the effect of ferromagnetic versus antiferromagnetic coupling of adjacent Fe 2+ and Fe 3+ cations could be determined. The molecular orbital results can be related to the polaron theory of solid state physics and the perturbation theory formalism used by Robin and Day (1967) and others to describe electron transfer in mixed valence compounds. Intervalence charge-transfer results from the overlap of Fe(3d) orbitals across the shared edges of adjacent FeO 6 polyhedra to give weak Fe-Fe bonds. Electron delocalization, however, requires that adjacent Fe cations be ferromagnetically coupled. Antiferromagnetic coupling results in distinguishable Fe 2+ and Fe 3+ cations. Electronic transitions between the Fe-Fe bonding and Fe-Fe antibonding orbitals results in the optically-induced intervalence charge transfer bands observed in the electronic spectra of mixed valence minerals. Such transitions are predicted to be polarized along the metal-metal bond direction, in agreement with experimental observations.

Physics and Chemistry of Minerals↗

USGS2024

Structural charge site influence on the interlayer hydration of expandable three-sheet clay minerals

Previous investigations have demonstrated the influences of interlayer cation composition, relative humidity, temperature, and magnitude of interlayer surface charge on the interlayer hydration of montmorillonites and vermiculites. It has been suggested that the sites of layer charge deficiencies may also have an influence upon the amount of hydration that can take place in the interlayers of expandable clay minerals. If the interlayer cation-to-layer bonds are considered as ideally electrostatic, the magnitude of the forces resisting expansion may be expressed as a form of Coulomb's law. If this effect is significant, expandable structures in which the charge-deficiency sites are predominantly in the tetrahedral sheet should have less pronounced swelling properties than should structures possessing charge deficiencies located primarily in the octahedral sheet. Three samples that differed in location of layer charge sites were selected for study. An important selection criterion was a non-correlation between tetrahedral charge sites and high surface-charge density, and between octahedral charge sites and low surface-charge density. The effects of differences in interlayer cation composition were eliminated by saturating portions of each sample with the same cations. Equilibrium (001) d values at controlled constant humidities were used as a measure of the relative degree of interlayer hydration. Although no correlation could be made between the degree of interlayer hydration and total surface-charge density, the investigation does not eliminate total surface-charge density as being significant to the swelling properties of three-sheet clay-mineral structures. The results do indicate a correlation between more intense expandability and predominance of charge deficiencies in the octahedral sheet. Conversely, less intense swelling behavior is associated with predominantly tetrahedral charge deficiencies.

Clays and Clay Minerals↗

USGS2024

Effect of chlorine in clay-mineral specimens prepared on silver metal-membrane mounts for X-ray powder diffraction analysis

Silver metal-membrane filters are commonly used as substrates in the preparation of oriented clay-mineral specimens for X-ray powder diffraction (XRD). They are relatively unaffected by organic solvent treatments and specimens can be prepared rapidly. The filter mounts are adaptable to automatic sample changers, have few discrete reflections at higher 20 angles, and, because of the high atomic number of silver, produce a relatively low overall background compared with other membrane filters, such as cellulose (Poppe and Hathaway, 1979). The silver metal-membrane filters, however, present some problems after heat treatment if either the filters or the samples contain significant amounts of chlorine. At elevated temperature, the chloride ions react with the silver substrate to form crystalline compounds. These compounds change the mass-absorption coefficient of the sample, reducing peak intensities and areas and, therefore, complicating the semiquantitative estimation of clay minerals. A simple procedure that eliminates most of the chloride from a sample and the silver metal-membrane substrate is presented here.

Clays and Clay Minerals↗

USGS2016

Mineral commodity summaries 2016

This report is the earliest Government publication to furnish estimates covering 2015 nonfuel mineral industry data. Data sheets contain information on the domestic industry structure, Government programs, tariffs, and 5-year salient statistics for more than 90 individual minerals and materials

Mineral Commodity Summaries↗

USGS2017

Mineral commodity summaries 2017

This report is the earliest Government publication to furnish estimates covering 2016 nonfuel mineral industry data. Data sheets contain information on the domestic industry structure, Government programs, tariffs, and 5-year salient statistics for more than 90 individual minerals and materials.

Mineral Commodity Summaries↗

USGS2018

Mineral commodity summaries 2018

This report is the earliest Government publication to furnish estimates covering 2017 nonfuel mineral industry data. Data sheets contain information on the domestic industry structure, Government programs, tariffs, and 5-year salient statistics for more than 90 individual minerals and materials.

Mineral Commodity Summaries↗