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 https://www.segweb.org/store/detail.aspx?id=EDOCREV18
The Esri ArcGIS 10.6 geodatabase contains 1 point and 2 polygon feature classes, 8 attribute tables, and 15 relationship classes. Relationship classes link tables using the Ftr_ID or Site_ID fields. Feature classes are also provided as Esri shapefiles; attribute tables are provided as Excel and comma-separated values (CSV) files. The description of each database layer (feature class) and attribute table is provided below, followed by general information about concepts and terms used in the development of the database.
DATABASE LAYERS AND TABLES
The Loc_Pt feature class contains point locations of mines, mineral occurrences (which includes deposits, prospects, and showings), and mineral regions, and the attribute information describing the location, source report, scale of the map used to obtain the location, and if the location has a polygonal footprint in the Loc_Poly feature class. In the database, all features have a point location, except for surface workings.
The Loc_Poly feature class contains footprints or polygons of areas, deposits, mineral districts, mining districts, placer districts, and prospects. If a source report shows a location as a polygon, the polygon is digitized, and the approximate centroid of the polygon is added to the Loc_Pt layer. Attribute information about the location is provided in the Loc_Pt layer. Mines are represented as points in the database, even when footprints are presented in source reports. Where possible, the approximate extent of the mining operation area, determined from imagery, is presented in the surface workings layer (see Loc_Poly_Sw).
The Loc_Poly_Sw feature class contains the approximate area of mining-related activity, or “surface workings” as shown on Esri imagery. These polygonal outlines have no corresponding point location in the database, nor do they have links to other tables. The attribute information for surface workings contains the date of the imagery and basic location information including state and county names. Surface workings must be at least 1,000 feet (300 meters) in one dimension to be digitized, and multiple workings that are 500 feet (150 meters) or less apart are combined into one outline. No attempt is made to distinguish between the types of surface workings (for example, roads, pits, leach pads, waste piles, etc.), even when presented in source reports.
The Site table is used to identify related features, such as a deposit and the mine(s) operating on it, or a mine and its related deposits. Each site has a unique identification value in the Site_ID field. The Site_ID is used in all tables except the References table. The Site table also indicates where information about a site occurs within the database. For example, if the Resources field in the Site table contains the value “Yes”, resource information is available in the Resources table.
The GeolMinOcc table contains information about the geology of mineral deposits, prospects, and showings. Every attempt is made to compile information as reported in the source report. For example, if one source report states the valuable material as "thorite and monazite" and another reports "cenosite", the attribute field Value_Mat will contain all values. The value in the Ref_ID field is the primary source report for the record, for example, Jackson and Christiansen (1993). All information in the record comes from the primary source report unless an attribute field value contains a footnote denoted as a number in parentheses. If a record value is followed by a footnote, the Ref_ID is given in the Remarks field. Full citations for source reports are provided in the References table.
The Resources table contains reported resource and reserve information for mineral deposits. Initial (or earliest resource data found by authors) and current resource data were compiled, even if information from intervening years was reported. Resource values were recorded as shown in source reports, including year reported, resource amount, units, and classification system(s). The definition of terms (for example, inferred, proven, probable, etc.) used in various resource classification systems may change through time. Resources 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) or the Joint Ore Reserves Committee Code (JORC Code). Inclusion of material in the database is for descriptive purposes only and does not imply endorsement by the U.S. Government. If resources or reserves are reported for a group of features rather than an individual deposit, the Ftr_ID will show “-1111” and the resource or reserve is assigned to the “site” or Site_ID that groups those deposits in the Site table. A value ending with “111” as a decimal trailer indicates the value was calculated by USGS authors. For example, if a grade is calculated by USGS authors to be 0.05 percent, the value recorded in the database will be 0.05111. Where a range in values is provided for attribute fields such as Mat_Amnt, Grade Contained, etc., the average of the range is reported within the field and the range of values is noted within the Remarks field. For consistency, resource values are converted to the International System of Units (SI units) by the USGS authors. When gold and silver values are reported in ounces in the source report, troy ounces were assumed when converting to SI units.
The Production table contains published production data for mines. Production is listed by commodity and reported as shown in the source reports. If production is reported annually, production is totaled by the USGS authors for the time period defined by the Year_From and Year_To values. If production is reported for a group of features, the Ftr_ID will show “-1111” and the production is assigned to the “site” or Site_ID that groups those mines in the Site table. A value ending with “111” as a decimal trailer indicates the value was calculated by USGS authors. For example, if a grade is calculated by USGS authors to be 0.05 percent, the value recorded in the database will be 0.05111. Where a range in values are provided for attribute fields such as Mat_Amnt, Grade Contained, etc., the average of the range is reported within the field and the range of values are noted within the Remarks field. For consistency, production values are converted to the International System of Units (SI units) by the USGS authors. When gold and silver values are reported in ounces in the source report, troy ounces were assumed when converting to SI units.
The History table contains information derived from publicly available sources regarding the status of a mine, prospect, deposit, or mineral region through time. Values in the Status field indicate a condition or phase for the time period stated in the Year_From and Year_To fields. This information may not reflect the current status of a feature. For example, if the attribute record shows the status of a mine is “Active” and the Year_From and Year_To dates are 1963 and 2001 respectively, the mine was active from 1963 to 2001; it is unknown if the mine is still active. The Last_Updt field shows the date that the record was last updated by the authors.
The Dep_Model table contains mineral deposit model and geoenvironmental model classifications for a deposit. When deposit model classifications could not be determined from published sources, the deposit model was assigned based on available geologic information and denoted as “USGS Authors (2018)” in the DpMD_RefID field.
The Descr_Sum table contains relevant descriptions found in source reports. These descriptions are attributed according to the type of description, such as Geology, Resource, Production, History, etc. Descriptions pertain to individual features or to larger sites. The authors do not paraphrase or combine descriptions, therefore, when a database feature is described in multiple reports, the feature will have multiple entries.
The References table contains the citation of the map or report(s) from which the point, polygon, or attribute information was obtained. The table also assigns a short reference Ref_ID which is used throughout the database.
Mines are a man-made feature associated with the process of extracting, processing, or concentrating ore materials. In this database, mines have a point location, and where possible, the polygon boundary showing the extent of surface workings identified from imagery. No attempt is made to distinguish specific mine features like pits, dumps, tailings, etc. within the surface workings outline.
Mineral occurrences, defined as a concentration of a mineral considered potentially valuable, are attributed as deposits, prospects, and showings in the database. Mineral deposits have defined size and grade indicated by current and (or) past production, and (or) a resource estimate. Prospects have sufficient data to describe at least two dimensions and the presence of useful or valuable minerals or materials. Showings have the occurrence of potentially valuable minerals as indicated by geological examination or analyses of samples.
Mineral regions are attributed as “areas”, mineral districts, mining districts, or placer districts. Areas have similar geology and deposit types. Mineral districts are areas, usually designated by name, defined by a group of deposits of similar type, origin, and/or commodity. Mining districts represent historic administrative areas organized by miners under the mining laws of the United States. Mining districts are typically an area containing a group of mines that exploited the same or related commodity. Placer districts are areas of placer mining operations. Placer district polygons were defined by the USGS authors. Mineral region polygons may overlap.
The locations of mines, mineral occurrences, and mineral regions are commonly represented as points in source maps and reports, and occasionally as footprints (polygon outlines). In this database, all features have a point location, and some have an additional polygonal footprint. Surface workings in the Loc_Poly_Sw feature class are the exception -- they do not have a corresponding point location or attribute information in the point layer. Otherwise, for points that have polygonal boundaries, the point attribute field Loc_Poly contains the value “Yes” and type of boundary is described in the field Poly_Def (for example, “Trace of placer districts” or “Outline of Indicated and Inferred Resource”).
Each point and polygon feature is uniquely identified by a Ftr_ID. The Site_ID is used to indicate groups of related features, or “sites”. Tables are linked (related) using the Ftr_ID or the Site_ID fields. Some tables have more than one record describing a feature. For example, a point denoting a mine location may have many records in the Production table summarizing the dates and amounts of material produced. The database is designed to allow the user to navigate from the point or polygon layers to the linked table information or from the tables to the point and polygon layers.
All database information is derived from publicly available sources. The Last_Updt field shows the date that the record information was last updated by the authors. Full citations are listed in the References table, and each citation is assigned a short citation, REF_ID that is used for identification in the database. With the exception of the Loc_Poly feature class, the primary reference(s) is noted in the Ref_ID field. Additional references are enumerated after attribute field values, and the corresponding short reference is in the Remarks field. For example, the Commodity field shows “rare earth elements; iron (1)”. This indicates the commodity “rare earth elements” was derived from the primary reference denoted in the Ref_ID field as “McKeown and Klemic (1956)” and “iron” was derived from a secondary reference denoted in the Remarks field as “(1) Jackson and Christiansen (1993)”.
There is no relevance to the order of data presented in lists. For example, if the Commodity field shows “rare earth elements; thorium; uranium”, that is the order in which those commodities were compiled by the authors and does not represent the order of importance. Additionally, in the GeolMinOcc table, lists in different fields do not relate. For example, if the Commodity field shows “rare earth elements; thorium; uranium”, the Value_Mat field may list related ore minerals in a different order. Similarly, the data lists reflect the order in which the information was compiled. Listed fields are present in the Site, Loc_Pt, and GeolMinOcc tables.
Field or attribute records that contain "Null" values in the file geodatabase, were checked for available data, and no data were found. In some cases, an entire field may contain no information. These "Null" fields are maintained in the database structure for consistency with related USGS products and for possible future use if information becomes available.
Two points may occupy the same location. This occurs when there is a deposit with a mine, and the location of either the mine or the deposit is unknown. For example, a report provides a map showing the location of a deposit. The report also provides production data for underground “Mine X” that is mining the deposit, but does not provide the location of “Mine X”. In this case, a second point representing “Mine X” is placed at the point location of the deposit.
Polygon features may overlap. Viewing polygons as outlines without color fills will show where polygon overlap occurs.
In the attribute section of this metadata, attribute fields from all tables and feature classes are listed in alphabetic order; corresponding feature classes and tables are listed in parentheses after the field name in the ‘Attribute_Label’. For example, “Mat_Amnt (Production, Resources)” indicates the attribute field Mat_Amnt (material amount) occurs in the Production table and in the Resources table.