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.

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

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 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

From June to September 2017, the United States Geological Survey (USGS) collected a total of 116 surficial sediment and bedrock samples from abandoned mine wastepiles, ephemeral channels below wastepiles, nearby outcrops, and background areas representative of the undisturbed lithology on the western slope of the northern half of the Oquirrh Mountain Range, approximately 20 miles southwest of Salt Lake City, Utah. The sample locations can be spatially clustered into four groups: the Bates Canyon group in the foothills below Bates Canyon; the Middle Canyon group in Middle Canyon; the Ridgeline group within the Bingham Mining District located at or near the Tooele-Salt Lake County border on the Oquirrh Mountain ridge; and the Stockton group within the historic Stockton Mining District (also known as the Rush Valley Mining District). Mining operations within the study area began in the mid-1860s and primarily targeted copper, gold, iron, lead and zinc deposits in the Pennsylvanian-Permian Oquirrh Group (Krahulec, 2018). Geochemical analyses were completed through a third-party contract by AGAT Laboratories. Samples were analyzed for 49 major, minor, and trace elements using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) methods (Ag, Al, As, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Hf, In, K, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Ni, P, Pb, Rb, S, Sb, Sc, Se, Sn, Sr, Ta, Tb, Te, Th, Ti, Tl, U, V, W, Y, Yb, Zn, Zr).

From June to September 2017, the United States Geological Survey (USGS) collected a total of 116 surficial sediment and bedrock samples from abandoned mine wastepiles, ephemeral channels below wastepiles, nearby outcrops, and background areas representative of the undisturbed lithology on the western slope of the northern half of the Oquirrh Mountain Range, approximately 20 miles southwest of Salt Lake City, Utah. The sample locations can be spatially clustered into four groups: the Bates Canyon group in the foothills below Bates Canyon; the Middle Canyon group in Middle Canyon; the Ridgeline group within the Bingham Mining District located at or near the Tooele-Salt Lake County border on the Oquirrh Mountain ridge; and the Stockton group within the historic Stockton Mining District (also known as the Rush Valley Mining District). Mining operations within the study area began in the mid-1860s and primarily targeted copper, gold, iron, lead and zinc deposits in the Pennsylvanian-Permian Oquirrh Group (Krahulec, 2018). Geochemical analyses were completed through a third-party contract by AGAT Laboratories. Samples were analyzed for 49 major, minor, and trace elements using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) methods (Ag, Al, As, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Hf, In, K, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Ni, P, Pb, Rb, S, Sb, Sc, Se, Sn, Sr, Ta, Tb, Te, Th, Ti, Tl, U, V, W, Y, Yb, Zn, Zr).