Version 4.0 of this data release provides descriptions of more than 200 mineral districts, mines, and mineral occurrences (deposits, prospects, and showings) within the United States that are reported to contain substantial enrichments of the rare earth elements (REEs). These mineral occurrences include mined deposits, exploration prospects, and other occurrences with notable concentrations of the REEs. The inclusion of a particular mineral occurrence in this database is not meant to imply that it has economic potential. Rather, these occurrences were included to capture the distribution and characteristics of the known, reported REEs deposits in the United States, which are diverse in their geology and resource potential. Concentrated, mineable deposits of the REEs are rare, such that most of the sites within this data release are for unmined locations where the published information may not contain thorough descriptions (Van Gosen and others, 2014). Therefore, decisions had to be made by the authors regarding the addition or exclusion of specific REE occurrences in the dataset, based principally on the available descriptions of the REE concentrations and the apparent size of the mineralized body. The level of detail of this type of information varied widely amongst the occurrences, ranging from general descriptions to detailed sampling and analysis of some deposits. The entries and descriptions in the database were derived from published papers, reports, data, and internet documents representing a variety of sources, including geologic and exploration studies described in State, Federal, and industry reports. Although an attempt was made to capture as many examples as possible, this dataset is a progress report that is part of an ongoing effort. The authors welcome additional published information in order to continually update and refine this dataset. In addition to the conventional resources described in this report, every year approximately 56,000 metric tons of REEs are mined, beneficiated, and put into solution, but not recovered, by operations associated with the global phosphate fertilizer industry (Emsbo and others, 2015, 2016). As indicated by Emsbo and others (2015, 2016), recovery of byproduct REEs from the phosphate industry has the potential to substantially increase the supply of REEs to the market. The significant increases in applications and demands for REEs has led to an increased interest in identifying new sources that include extraction not only from mineral deposits, but also the potential for REE extraction from coal-based resources, and recycling of products containing REEs. The Department of Energy is currently (2019) evaluating technologies to recover REEs and other critical minerals from coal and coal-based resources (https://www.netl.doe.gov/coal/rare-earth-elements). Recycling efforts have focused on recovering REEs from light bulbs and electronics. The dataset provided in this data release is restricted to non-fuel, REE-bearing mineral deposits and does not include energy resources (such as coal). Van Gosen, B.S., Verplanck, P.L., Long, K.R., Gambogi, Joseph, and Seal, R.R., II, 2014, The rare-earth elements—Vital to modern technologies and lifestyles: U.S. Geological Survey Fact Sheet 2014–3078, 4 p., https://dx.doi.org/10.3133/fs20143078. Emsbo, Poul, McLaughlin, P.I., Breit, G.N., du Bray, E.A., and Koenig, A.E., 2015, Rare earth elements in sedimentary phosphate deposits—Solution to the global REE crisis?: Gondwana Research, v. 27, p. 776–785, accessed March 13, 2019, at https://doi.org/10.1016/j.gr.2014.10.008. Emsbo, Poul, McLaughlin, P.I., du Bray, E.A., Anderson, E.D., Vandenbroucke, T.R.A., and Zielinski, 2016, Rare earth elements in sedimentary phosphorite deposits—A global assessment, chap. 5 of Verplanck, P.L, and Hitzman, M.W., eds., Rare earth and critical elements in ore deposits: Reviews in Economic Geology, v. 18, p. 101–114, accessed March 13, 2019, at

This data release provides descriptions of more than 100 mining districts, mines, and mineral occurrences (deposits and prospects) within the United States that are reported to contain enrichments of rhenium (Re). These mineral occurrences include mined deposits, exploration prospects, and other occurrences with notable concentrations of rhenium. The inclusion of a particular mineral occurrence in this database is not meant to imply that it has economic potential. Rather, these occurrences were included to capture the distribution and characteristics of the known, reported rhenium occurrences in the United States. Rhenium is one of the rarest elements in the Earth's crust. Most rhenium occurs in the mineral molybdenite, where the rhenium substitutes for molybdenum. Rhenium is produced as a byproduct from roasting molybdenum concentrates recovered from mining porphyry copper deposits. Because the United States contains many porphyry copper mines and deposits, decisions had to be made by the authors regarding the addition or exclusion of copper and molybdenum deposits in the dataset, based principally on the published descriptions of the occurrence of rhenium in those deposits. The level of detail describing the rhenium occurrence varies widely, ranging from rhenium resources to general descriptions about the occurrence of rhenium. The entries and descriptions in the database were derived from published papers, reports, data, and internet documents, published from 1917 to 2018, representing a variety of sources, including geologic and exploration studies described in State, Federal, and industry reports. Although an attempt was made to capture as many examples as possible, this dataset is a progress report that is part of an ongoing effort. The authors welcome additional published information in order to continually update and refine this dataset.

This data release provides descriptions of more than 100 mining districts, mines, and mineral occurrences (deposits and prospects) within the United States that are reported to contain enrichments of rhenium (Re). These mineral occurrences include mined deposits, exploration prospects, and other occurrences with notable concentrations of rhenium. The inclusion of a particular mineral occurrence in this database is not meant to imply that it has economic potential. Rather, these occurrences were included to capture the distribution and characteristics of the known, reported rhenium occurrences in the United States. Rhenium is one of the rarest elements in the Earth's crust. Most rhenium occurs in the mineral molybdenite, where the rhenium substitutes for molybdenum. Rhenium is produced as a byproduct from roasting molybdenum concentrates recovered from mining porphyry copper deposits. Because the United States contains many porphyry copper mines and deposits, decisions had to be made by the authors regarding the addition or exclusion of copper and molybdenum deposits in the dataset, based principally on the published descriptions of the occurrence of rhenium in those deposits. The level of detail describing the rhenium occurrence varies widely, ranging from rhenium resources to general descriptions about the occurrence of rhenium. The entries and descriptions in the database were derived from published papers, reports, data, and internet documents, published from 1917 to 2018, representing a variety of sources, including geologic and exploration studies described in State, Federal, and industry reports. Although an attempt was made to capture as many examples as possible, this dataset is a progress report that is part of an ongoing effort. The authors welcome additional published information in order to continually update and refine this dataset.

In response to Executive Order 13817 of December 20, 2017, the U.S. Geological Survey (USGS) coordinated with the Bureau of Land Management (BLM) to identify 35 nonfuel minerals or mineral materials considered critical to the economic and national security of the United States (U.S.). Acquiring information on possible domestic sources of these critical minerals is the basis of the USGS Earth Mapping Resources Initiative (Earth MRI). The program, which partners the USGS with State Geological Surveys, federal agencies, and the private sector, aims to collect new geological, geophysical, and topographic (lidar) data in key areas of the U.S. to stimulate mineral exploration and production of critical minerals. The first phase of Earth MRI focuses on the study of rare-earth elements (REE). The USGS has identified broad areas within the U.S. to target acquisition of geologic mapping, geophysical data, and (or) detailed topographic information to aid research, mineral exploration, and evaluation of REE potential in these areas. Focus areas were defined using existing geologic data on known REE deposits in the U.S. The focus areas are provided as geospatial data supported by tables that summarize what is known about the REE potential and brief descriptions of data gaps that could be addressed by the Earth MRI program. A full discussion of Earth MRI and the rationale and methods used to develop the geospatial data are provided in the following report: Hammarstrom, J.H., and Dicken, C.L., 2019, Focus areas for data acquisition for potential domestic sources of critical minerals—Rare earth elements, chap. A of U.S. Geological Survey, Focus areas for data acquisition for potential domestic sources of critical minerals: U.S. Geological Survey Open-File Report 2019–1023, 11 p., https://doi.org/10.3133/ofr20191023A.

In response to Executive Order 13817 of December 20, 2017, the U.S. Geological Survey (USGS) coordinated with the Bureau of Land Management (BLM) to identify 35 nonfuel minerals or mineral materials considered critical to the economic and national security of the United States (U.S.). Acquiring information on possible domestic sources of these critical minerals is the basis of the USGS Earth Mapping Resources Initiative (Earth MRI). The program, which partners the USGS with State Geological Surveys, federal agencies, and the private sector, aims to collect new geological, geophysical, and topographic (lidar) data in key areas of the U.S. to stimulate mineral exploration and production of critical minerals. The first phase of Earth MRI focuses on the study of rare-earth elements (REE). The USGS has identified broad areas within the U.S. to target acquisition of geologic mapping, geophysical data, and (or) detailed topographic information to aid research, mineral exploration, and evaluation of REE potential in these areas. Focus areas were defined using existing geologic data on known REE deposits in the U.S. The focus areas are provided as geospatial data supported by tables that summarize what is known about the REE potential and brief descriptions of data gaps that could be addressed by the Earth MRI program. A full discussion of Earth MRI and the rationale and methods used to develop the geospatial data are provided in the following report: Hammarstrom, J.H., and Dicken, C.L., 2019, Focus areas for data acquisition for potential domestic sources of critical minerals—Rare earth elements, chap. A of U.S. Geological Survey, Focus areas for data acquisition for potential domestic sources of critical minerals: U.S. Geological Survey Open-File Report 2019–1023, 11 p., https://doi.org/10.3133/ofr20191023A.

This report and digital data release presents 286 new geochemical analyses on historic U.S. Bureau of Mines (USBM) samples, including 93 rock, 110 stream sediment, 52 soil, and 28 heavy mineral concentrate (pan concentrate) samples, as well as 3 samples of indeterminate type. These samples were originally collected as part of studies by the USBM in the Circle mining district, western Crazy Mountains, and Lime Peak area of the White Mountains, Circle Quadrangle, east-central Alaska. Historic USBM sample materials were retrieved by DGGS from the DGGS Geologic Materials Center (GMC), where the USBM samples were transferred as part of the federally funded Minerals Data and Information Rescue in Alaska (MDIRA) program in the late 1990s and early 2000s. The text and analytical data and tables associated with this report are being released in digital format as PDF files and .csv files. We provide analytical data, detection limits and, when available, the method documentation provided to us by the lab. We also provide the sample location in geographic coordinates, the sample material cited by the originating literature, a reference to the originating report, and the type of sample material that was obtained from the archive and sent to the lab.

This data release provides data for the single site in the United States (U.S.) that has public record of germanium (Ge) production. Germanium, which is currently classified as a critical mineral in the U.S., is also extracted as a byproduct from deposits in Alaska, Washington, and Tennessee. However, there is no public information that documents germanium production from these deposits. Current annual production of refined germanium is led by China at 85,000 tons, while estimates place U.S. reserves near 2,500 tons. Reported production of germanium in the U.S. is limited to one site, the Apex mine in Washington County, Utah. The Apex mine produced gallium (Ga) and germanium as primary products during the mid-1980s. Since its closure, germanium recovery has been restricted to refining processes of ore concentrates and recycling of waste scrap both in and outside the U.S. (U.S. Geological Survey, 2020). As a part of the process set forth by Executive Order 13817, the USGS National Minerals Information Center (NMIC) identified germanium as a critical mineral (Department of the Interior, 2018) due to the import reliance and importance in the sectors of defense, manufacturing, and telecommunications (Fortier and others, 2018). Germanium is used for strategic, consumer, and commercial applications due to its high refractive index, transparency to infrared light, and properties as a semiconductor. Most notably, germanium is a major component in infrared devices, fiber optic cables, and PET plastics (Melcher and Buchholz, 2014). As of 2019, the U.S. maintains greater than 50% reliance on imported germanium from countries such as Belgium and China who were the main U.S. suppliers between 2015–2018. Germanium is imported to the U.S. as germanium metal and dioxide for consumption (U.S. Geological Survey, 2020). Some germanium is recovered from recycling of scrap during the manufacturing process, such as the manufacture of fiber-optic cables (Mercer, 2015). The element germanium largely occurs as a geochemical substitute in various sulfide minerals, primarily in the mineral sphalerite (ZnS), with minor inclusion in silicate minerals. The greatest germanium concentrations occur in Kipushi-type deposits, principally in oxidation zones of sulfide ore (Höll and others, 2007). The largest past producers of germanium from Kipushi-type deposits occurred in Kipushi, Democratic Republic of the Congo, and Tsumeb, Namibia. These deposits host 60 million tonnes (t) at 100–200 parts per million (ppm) Ge and 28 million t at 50–150 ppm Ge, respectively. Currently, germanium is produced as a byproduct of zinc-bearing ore deposits. Acid mine drainage may have elevated signatures of germanium because of germanium’s strong association to sulfide minerals (Shanks and others, 2017). Germanium is also recovered from lignite and coal deposits worldwide (Melcher and Buchholz, 2014). The entries and descriptions in the database were derived from published papers, reports, data, and internet documents representing a variety of sources, including geologic and exploration studies described in State, Federal, and industry reports. Production and resource information extracted from older sources might not be compliant with current rules and guidelines in minerals industry standards such as National Instrument 43-101 (NI 43-101). The presence of a germanium mineral deposit in this database is not meant to imply that the deposit is currently economic. Inclusion of material in the database is for descriptive purposes only and does not imply endorsement by the U.S. Government. The authors welcome additional published information in order to continually update and refine this dataset. Department of the Interior, 2018, Final list of critical minerals 2018: Federal Register Notice 83 FR 23295, no. 97, p. 23295–23296, https://www.federalregister.gov/d/2018-10667. Fortier, S.M., Nassar, N.T., Lederer, G.W., Brainard, J., Gambogi, J., and McCullough, E.A., 2018, Draft critical

This data release provides data for the single site in the United States (U.S.) that has public record of germanium (Ge) production. Germanium, which is currently classified as a critical mineral in the U.S., is also extracted as a byproduct from deposits in Alaska, Washington, and Tennessee. However, there is no public information that documents germanium production from these deposits. Current annual production of refined germanium is led by China at 85,000 tons, while estimates place U.S. reserves near 2,500 tons. Reported production of germanium in the U.S. is limited to one site, the Apex mine in Washington County, Utah. The Apex mine produced gallium (Ga) and germanium as primary products during the mid-1980s. Since its closure, germanium recovery has been restricted to refining processes of ore concentrates and recycling of waste scrap both in and outside the U.S. (U.S. Geological Survey, 2020). As a part of the process set forth by Executive Order 13817, the USGS National Minerals Information Center (NMIC) identified germanium as a critical mineral (Department of the Interior, 2018) due to the import reliance and importance in the sectors of defense, manufacturing, and telecommunications (Fortier and others, 2018). Germanium is used for strategic, consumer, and commercial applications due to its high refractive index, transparency to infrared light, and properties as a semiconductor. Most notably, germanium is a major component in infrared devices, fiber optic cables, and PET plastics (Melcher and Buchholz, 2014). As of 2019, the U.S. maintains greater than 50% reliance on imported germanium from countries such as Belgium and China who were the main U.S. suppliers between 2015–2018. Germanium is imported to the U.S. as germanium metal and dioxide for consumption (U.S. Geological Survey, 2020). Some germanium is recovered from recycling of scrap during the manufacturing process, such as the manufacture of fiber-optic cables (Mercer, 2015). The element germanium largely occurs as a geochemical substitute in various sulfide minerals, primarily in the mineral sphalerite (ZnS), with minor inclusion in silicate minerals. The greatest germanium concentrations occur in Kipushi-type deposits, principally in oxidation zones of sulfide ore (Höll and others, 2007). The largest past producers of germanium from Kipushi-type deposits occurred in Kipushi, Democratic Republic of the Congo, and Tsumeb, Namibia. These deposits host 60 million tonnes (t) at 100–200 parts per million (ppm) Ge and 28 million t at 50–150 ppm Ge, respectively. Currently, germanium is produced as a byproduct of zinc-bearing ore deposits. Acid mine drainage may have elevated signatures of germanium because of germanium’s strong association to sulfide minerals (Shanks and others, 2017). Germanium is also recovered from lignite and coal deposits worldwide (Melcher and Buchholz, 2014). The entries and descriptions in the database were derived from published papers, reports, data, and internet documents representing a variety of sources, including geologic and exploration studies described in State, Federal, and industry reports. Production and resource information extracted from older sources might not be compliant with current rules and guidelines in minerals industry standards such as National Instrument 43-101 (NI 43-101). The presence of a germanium mineral deposit in this database is not meant to imply that the deposit is currently economic. Inclusion of material in the database is for descriptive purposes only and does not imply endorsement by the U.S. Government. The authors welcome additional published information in order to continually update and refine this dataset. Department of the Interior, 2018, Final list of critical minerals 2018: Federal Register Notice 83 FR 23295, no. 97, p. 23295–23296, https://www.federalregister.gov/d/2018-10667. Fortier, S.M., Nassar, N.T., Lederer, G.W., Brainard, J., Gambogi, J., and McCullough, E.A., 2018, Draft critical

This spatial database "usgs_Global_REE.gdb" was created for use in a geographic information system (GIS) to support research on global rare earth deposits and occurrences by the U.S. Geological Survey. This inventory documents the geologic occurrence of rare earths, including mineralogy, type of deposit or occurrence, host rocks and alteration, and any quantitative data related to size and grade from publicly available data. Rare earths, as used in this report, includes the chemically similar lanthanide group of elements, as well as yttrium. Databases that summarize the distribution of known occurrences and their geologic setting are an integral part of a geologically-based evaluation of undiscovered mineral resources. The distribution of known occurrences allows us to understand the factors that control their distributions, the degree of variation within deposit types, and, through the use of analogy, to forecast areas where similar deposits and occurrences may occur. The geodatabase contains more than 3100 records with latitudes and longitudes and more than 800 records without plottable locations. Spatial and descriptive data for 3100 rare earth deposits and occurrences around the world are stored in the rare earth geodatabase feature class "Global_REE" for use in a geographic information system (GIS). In addition, 820 deposits and occurrences for which no location was found or determined are stored in a geodatabase table "Global_REE_nonspatial_table" and the over 1590 references are stored in a geodatabase table "All_Global_REE_references" which were used to compile these data. The databases of rare earth deposits and occurrences provides descriptive information where available on mineralogy, host and associated rocks and ages, alteration, sizes and grades of resources and production, and references; the data in the spatial database include location.

This spatial database "usgs_Global_REE.gdb" was created for use in a geographic information system (GIS) to support research on global rare earth deposits and occurrences by the U.S. Geological Survey. This inventory documents the geologic occurrence of rare earths, including mineralogy, type of deposit or occurrence, host rocks and alteration, and any quantitative data related to size and grade from publicly available data. Rare earths, as used in this report, includes the chemically similar lanthanide group of elements, as well as yttrium. Databases that summarize the distribution of known occurrences and their geologic setting are an integral part of a geologically-based evaluation of undiscovered mineral resources. The distribution of known occurrences allows us to understand the factors that control their distributions, the degree of variation within deposit types, and, through the use of analogy, to forecast areas where similar deposits and occurrences may occur. The geodatabase contains more than 3100 records with latitudes and longitudes and more than 800 records without plottable locations. Spatial and descriptive data for 3100 rare earth deposits and occurrences around the world are stored in the rare earth geodatabase feature class "Global_REE" for use in a geographic information system (GIS). In addition, 820 deposits and occurrences for which no location was found or determined are stored in a geodatabase table "Global_REE_nonspatial_table" and the over 1590 references are stored in a geodatabase table "All_Global_REE_references" which were used to compile these data. The databases of rare earth deposits and occurrences provides descriptive information where available on mineralogy, host and associated rocks and ages, alteration, sizes and grades of resources and production, and references; the data in the spatial database include location.