These data comprise chemical analyses in weight percent of oxides, as well as chlorine and fluorine, conducted using a JEOL JXA-8900 electron microprobe analyzer (EPMA) on amphiboles, pyroxenes, and carbonates in the Ironwood Iron-Formation.

These data comprise various SEM images from drill cores and outcrops in the Ironwood Iron-Formation.

These data comprise various SEM images from drill cores and outcrops in the Ironwood Iron-Formation.

This dataset comprises photomicrographs from drill core and outcrop samples from the Ironwood Iron-Formation in the Gogebic Iron Range, Wisconsin, USA.

This dataset comprises various energy-dispersive spectroscopy (EDS) analyses from drill core and outcrop samples in the Ironwood Iron-Formation, Gogebic Iron Range, Wisconsin, USA.

Mine waste, including mill tailings, could host substantial critical mineral resources. Developing an understanding of the mineral hosts and occurrence of critical minerals in mine waste is essential to evaluating their resource potential. Volcanogenic massive sulfide (VMS) and sedimentary-exhalative (SEDEX) deposits are important global sources of copper, zinc, lead, gold, and silver, and may contain economic to sub-economic concentrations of critical mineral commodities including cobalt, nickel, arsenic, antimony, and bismuth. Waste material from these deposit types typically contains significant concentrations of the gangue sulfide minerals pyrite and pyrrhotite, which are known to host trace to weight-percent concentrations of some critical minerals such as Co, Ni, or As. Pyrite and pyrrhotite also represent a potential environmental liability when associated with mine waste because their weathering generates acid-mine drainage. Identifying additional value in these minerals may encourage mine waste reprocessing, helping to mitigate their environmental effects. Comparing the geochemistry of pyrite and pyrrhotite in tailings and ore samples allows the composition of the ore material to be correlated to the composition and critical mineral endowment of existing or potential waste from that deposit. This data release provides micro-analytical geochemical information on pyrite and pyrrhotite in tailings and ores from volcanogenic massive sulfide and sedimentary-exhalative zinc-lead deposits in order to determine the mineralogical hosts (that is, inclusions or in solid solution within the crystal lattice) and range in concentrations of critical minerals. Pyrite and pyrrhotite grains in tailings and ore samples from deposits in the United States (Ducktown VMS, Elizabeth VMS, Bald Mountain VMS, Callahan VMS, Cofer VMS, Iron Mountain VMS, Red Dog SEDEX), Finland (Kotalahti VMS, Luikonlahti VMS, Hammaslahti VMS), Canada (Corbet VMS, Kidd Creek VMS, Anvil-Faro SEDEX, Sullivan SEDEX), and Australia (McArthur River SEDEX) were analyzed for their trace element chemistry using laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Additionally, pyrites in samples from the epithermal Katherine mine in AZ, USA were analyzed by LA-ICP-MS. These data represent spot chemical analyses in parts per million (ppm) collected using an Applied Spectra Resolution S155 laser-ablation system and an Agilent 8900 mass spectrometer at the USGS L-TRACE laboratory in Denver, CO. Raw data were analyzed using the software program LADR (https://norsci.com/?p=ladr). One .csv file is provided (PyPo-VMS-SEDEX_2024_LAICPMS.csv) that detail the measurements collected, analytical error, and measurement conditions. Samples from the Elizabeth (USA), Cofer (USA), and Hammaslahti (FIN) VMS deposits, and the Anvil-Faro SEDEX deposit (CAN) were analyzed using electron microprobe analyses. These data represent chemical analyses in weight percent (wt%) collected using a JEOL 8530F Plus SuperProbe electron probe microanalyzer (EPMA) in the USGS Denver Microbeam Laboratory in Denver, CO on pyrite and pyrrhotite grains in tailings. A text file of results is provided in comma-separated by value (csv) format. The file has the name “PyPo-VMS-SEDEX_2023_EPMA.csv”.

The iron oxide-apatite (IOA) deposits near Mineville in the Adirondack Mountains, New York, have been of interest for their rich magnetite ore since the mid-1700s but have attracted renewed attention due to their potential as rare earth element (REE) resources (McKeown and Klemic, 1956; Lupulescu and others, 2016; Taylor and others, 2018). Apatite is the main REE-host and is found in variable concentrations within ore seams of the regional magnetite deposits. Some apatite crystals are unaltered, relatively homogenous, and inclusion-free, whereas other deposits contain heterogenous apatite with zones of abundant secondary mineral inclusions that were formed through metasomatic reactions with the apatite after initial precipitation. The heterogeneous apatite crystals may have inclusion-free bright zones and intermediate zones in back-scattered electron imagery (BSE), and dark BSE zones that contain inclusions of monazite and thorite. Apatite crystals from twenty-seven samples, including twenty-four ore and three rock samples from a total of nineteen different ore deposits, were analyzed by electron microprobe to obtain their major and minor element geochemistry. Additionally, some magmatic apatite crystals from the ore-hosting Lyon Mountain Granite Gneiss were analyzed for comparison with the ore apatite. The electron microprobe data was collected by personnel of the Southwest Region Geology, Geophysics, and Geochemistry Science Center in Denver, Colorado, for the U.S. Geological Survey (USGS) Mineral Resources Program (MRP). A JEOL 8900 Electron Microprobe with five wavelength dispersive analyzers operated at 20keV accelerating voltage, a 50-nA current (measured on the Faraday cup), and an electron beam diameter of 10 micrometers was utilized. All analyzed crystals are considered fluorapatite, with fluorine contents ranging from approximately 3.5 to 6.6%. Some apatite crystals from ore contain greater than 15% total REE, whereas some others contain less than 1%. Commonly, Y, La, Ce, and Nd are the most abundant REE in the apatite crystals. The magmatic apatite crystals are notably purer with low contents of actinides, REE, and other common minor impurities. Analyses that contained total elemental weight percentages between 97% to 103% were accepted; those analyses with poor totals falling outside of this range were rejected. The different zones within heterogeneous apatite crystals contained lower concentrations of REE and other minor element components in the dark BSE zones than in the bright BSE zones, but both zones had nearly parallel REE profiles. The zones of differing BSE brightness are interpreted to be caused by metasomatic alteration. Although the REE profiles were consistent for a given sample, variations in total REE content and overall chemistry were noted between different deposits and even different ore seams within a given deposit.

The iron oxide-apatite (IOA) deposits near Mineville in the Adirondack Mountains, New York, have been of interest for their rich magnetite ore since the mid-1700s but have attracted renewed attention due to their potential as rare earth element (REE) resources (McKeown and Klemic, 1956; Lupulescu and others, 2016; Taylor and others, 2018). Apatite is the main REE-host and is found in variable concentrations within ore seams of the regional magnetite deposits. Some apatite crystals are unaltered, relatively homogenous, and inclusion-free, whereas other deposits contain heterogenous apatite with zones of abundant secondary mineral inclusions that were formed through metasomatic reactions with the apatite after initial precipitation. The heterogeneous apatite crystals may have inclusion-free bright zones and intermediate zones in back-scattered electron imagery (BSE), and dark BSE zones that contain inclusions of monazite and thorite. Apatite crystals from twenty-seven samples, including twenty-four ore and three rock samples from a total of nineteen different ore deposits, were analyzed by electron microprobe to obtain their major and minor element geochemistry. Additionally, some magmatic apatite crystals from the ore-hosting Lyon Mountain Granite Gneiss were analyzed for comparison with the ore apatite. The electron microprobe data was collected by personnel of the Southwest Region Geology, Geophysics, and Geochemistry Science Center in Denver, Colorado, for the U.S. Geological Survey (USGS) Mineral Resources Program (MRP). A JEOL 8900 Electron Microprobe with five wavelength dispersive analyzers operated at 20keV accelerating voltage, a 50-nA current (measured on the Faraday cup), and an electron beam diameter of 10 micrometers was utilized. All analyzed crystals are considered fluorapatite, with fluorine contents ranging from approximately 3.5 to 6.6%. Some apatite crystals from ore contain greater than 15% total REE, whereas some others contain less than 1%. Commonly, Y, La, Ce, and Nd are the most abundant REE in the apatite crystals. The magmatic apatite crystals are notably purer with low contents of actinides, REE, and other common minor impurities. Analyses that contained total elemental weight percentages between 97% to 103% were accepted; those analyses with poor totals falling outside of this range were rejected. The different zones within heterogeneous apatite crystals contained lower concentrations of REE and other minor element components in the dark BSE zones than in the bright BSE zones, but both zones had nearly parallel REE profiles. The zones of differing BSE brightness are interpreted to be caused by metasomatic alteration. Although the REE profiles were consistent for a given sample, variations in total REE content and overall chemistry were noted between different deposits and even different ore seams within a given deposit.

This dataset contains results from electron microprobe analyses for expanded and unexpanded vermiculite samples. These data are provide for samples of vermiculite ore, expanded vermiculite insulation, horticultural products, aggregate, and packing materials derived from mines near Enoree, South Carolina; Libby, Montana; Louisa, Virginia; Palabora, South Africa; Jiangsu, China; and Llano, Texas. An ASCII text file of results is provided in comma-separated by value (csv) format. The file has the name “vermiculite_probe_microanalyses_data.csv”.

This dataset contains results from electron microprobe analyses for expanded and unexpanded vermiculite samples. These data are provide for samples of vermiculite ore, expanded vermiculite insulation, horticultural products, aggregate, and packing materials derived from mines near Enoree, South Carolina; Libby, Montana; Louisa, Virginia; Palabora, South Africa; Jiangsu, China; and Llano, Texas. An ASCII text file of results is provided in comma-separated by value (csv) format. The file has the name “vermiculite_probe_microanalyses_data.csv”.