This U.S. Geological Survey (USGS) data release provides the descriptions of 11 U.S. sites that include mineral regions, mines, and mineral occurrences that contain enrichments of niobium (Nb). To be included in this data release, a site must have a contained resource and (or) past production of Nb metal greater than 10,000 metric tons, which was the approximate consumption of Nb in the U.S. in 2019 (U.S. Geological Survey, 2020). Sites in this dataset occur in Alaska, Arkansas, Colorado, Nebraska, and Texas.
Niobium primarily occurs in oxide minerals of the pyrochlore group, which are most commonly found in carbonatites and alkaline granite-syenite complexes. Globally, the largest Nb deposits occur in Brazil and Canada. In Brazil, the Barreiro carbonatite complex hosts the Araxá deposit that contains more than 460 million metric tons of ore with an average grade of 2.48 percent Nb2O5 (Schulz and others, 2017). The world’s leading producer of Nb outside of Brazil is the Niobec Mine in Quebec, Canada. The Niobec deposit occurs in the Saint-Honoré carbonatite complex, where pyrochlore is the main niobium-bearing mineral; the ore body contains more than 400 million metric tons with an average grade of 0.42 percent Nb2O5 (Schulz and others, 2017). In comparison, the largest known Nb deposit in the U.S. is the Iron Hill deposit in Colorado, which has been prospected for titanium, Nb, rare earth elements and thorium. There are no current U.S. producers of Nb, but the Elk Creek project in Nebraska is in the furthest stage of development. If Elk Creek comes online, it will be the first recorded producer of Nb in the U.S. since the 1950s.
Niobium is necessary for strategic, consumer, and commercial applications. The primary use for Nb is for the production of high strength steel alloys used in pipelines, transportation infrastructure, and structural applications (Schulz and others, 2017). As of 2019, the U.S. maintains a history of being 100 percent net import reliant on Nb from countries, such as Brazil and Canada. Niobium is imported to the U.S. as Nb minerals, oxides, and ferroniobium (U.S. Geological Survey, 2020).
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. 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). The inclusion of a Nb mineral deposit in this database is not meant to imply that the deposit is currently economic. Rather, these deposits were included to capture the characteristics of the largest Nb deposits in the United States. 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.
Schulz, K.J., Piatak, N.M., and Papp, J.F., 2017, Niobium and tantalum, chap. M of Schulz, K.J., DeYoung, J.H., Jr., Seal, R.R., II, and Bradley, D.C., eds., Critical mineral resources of the United States—Economic and environmental geology and prospects for future supply: U.S. Geological Survey Professional Paper 1802, p. M1–M34,
https://doi.org/10.3133/pp1802M.
U.S. Geological Survey, 2020, Mineral commodity summaries 2020: U.S. Geological Survey, 200 p.,
https://doi.org/10.3133/mcs2020.
The Esri ArcGIS 10.8.1 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. Metadata is provided in extensible markup language (XML), hypertext markup language (HTML), and text-formatted (TXT) formats.
DATABASE LAYERS AND TABLES
The Loc_Pt feature class contains point locations of mineral regions, mineral occurrences (deposits), and mine features, 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 point locations, except for surface workings.
The Loc_Poly feature class contains footprints or polygons of areas, deposits, and mining districts. 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 (Loc_Poly_Sw) layer.
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 (ft) (300 meters[m]) in one dimension to be digitized, and multiple workings that are 500 ft (150 m) 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. No surface workings were delineated in this data release.
The Dep_Model table contains mineral deposit model and geoenvironmental model classifications that are models established and used by the USGS for deposits included in the database.
The Descr_Sum table contains relevant descriptions found in source reports. These descriptions are attributed according to the type of description, such as Geology, History, Production, Resources, etc. Descriptions pertain to individual features or to larger sites. The authors do not paraphrase nor combine descriptions, and therefore, when a database feature is described in multiple reports, the feature will have multiple entries.
The GeolMinOcc table contains information about the geology of mineral deposits and prospects. Every attempt was made to compile information as reported in the source report. For example, if one source report states the valuable material as "bastnaesite, galena, sphalerite", and another reports "columbite", 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, " Robinson and others (2011)". All information in the record comes from the primary source report unless an attribute field value contains a number in parentheses. This number denotes another source report whose Ref_ID is given in the Remarks field. Full citations for source reports are provided in the References table and adhere to USGS citation style.
The History table contains information derived from publicly available sources regarding the status of a mineral region, mineral occurrence, or mine feature 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 1957 and 1971 respectively, the mine was active from 1957 and 1971; 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 Production table contains published production data for mines. Production is listed by commodity and reported as shown in the source reports. Reported production values are totaled by the USGS authors for the time period defined by the Year_From and Year_To fields. 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 on the Site table. The contained SI commodity amount (CntSIComAm) for the contained SI commodity (CntSICom) has been provided in one consistent unit (metric tons) for the user; these conversions are typically calculated by USGS authors. 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. Conversion factors used by USGS authors can be found on the USGS_Niobium_Merged_Excel file under the Conversions tab. Decimal trailers are not reported in the Entity and Attribute section for ranges. 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 SI units by the USGS authors.
The References table contains the citation of the map or report(s) from which the point, polygon, or attribute information is obtained. The table also assigns a short reference (Ref_ID) that is used throughout the database. This table does not have a relationship class allowing the user to relate to other tables because Ref_IDs from tables such as the Production table may have multiple references.
The Resources table contains reported resource data for mineral deposits. Data are compiled for the most recent mineral resource estimate when available. 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 NI 43-101 or the Joint Ore Reserves Committee Code (JORC Code). The way the resource is reported dictates the number of records for each deposit. For example, if data from a single deposit are reported for an inferred resource and a proven reserve, data from both classifications will be reported as separate records, unless it is stated that the proven reserve is inclusive of the inferred resource. If resource data are reported for a group of features rather than an individual deposit, the Ftr_ID will show "-1111" and the resource is assigned to the "site" or Site_ID that groups those deposits on the Site table. The attribute field CntSIComAm has been provided in one consistent unit (metric tons) for the user; these conversions are typically calculated by USGS authors. A value ending with "111" as a decimal trailer indicates the value was calculated by USGS authors. For example, if a value in the Grade field is calculated by USGS authors to be 0.05 percent, then the value recorded in the database will be 0.05111. Conversion factors used by the USGS authors can be found on the USGS_Niobium_Merged_Excel file under the Conversions tab. Decimal trailers are not reported in the Entity and Attribute section for ranges. 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. Inclusion of material in the database is for descriptive purposes only and does not imply endorsement by the U.S. Government.
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. A Site_ID is also assigned to mineral regions, such as mining districts, which are represented as a single polygon or point feature in the database. The Site_ID is used in all tables except the References table and Loc_Poly_Sw feature class. 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.
GENERAL INFORMATION
Mineral regions may be a mineralized area, a mineral district, or a mining district. Mineral areas have similar geology and deposit types. Mineral districts are usually named and are 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. Mining district polygons may overlap.
Mine features are man-made features associated with the process of extracting, processing, or concentrating ore materials. In this database, mine features 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 such as pits, dumps, tailings, etc. within the surface workings outline.
Mineral occurrences, defined as a concentration of a mineral considered potentially valuable, can be deposits, prospects, or showings in USGS mineral deposit databases (USMIN). Mineral deposits have a defined size and may have a grade indicated by current and (or) past production, and (or) a resource estimate.
The locations of mineral regions, mine features, and mineral occurrences 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 Loc_Pt feature class. Otherwise, for points that have polygonal boundaries, the Loc_Pt feature class attribute field Loc_Poly contains the value "Yes" and the boundary definition is described in the field Poly_Def field. For example, "Approximate extent of the Powderhorn district", or "Approximate extent of region on the map".
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 that summarize 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 data are derived from publicly available sources. The Last_Updt field shows the date that the record was last updated by the USGS 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. Except for 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. As an example, one Commodity field shows "niobium; scandium (1); titanium (1)". This indicates the commodities "niobium" was derived from the primary reference denoted in the Ref_ID field as "Drenth (2014)" and "scandium and titanium" was derived from a secondary reference denoted in the Remarks field as "(1) Brown and others (2019) ".
In the GeolMinOcc table, lists in different fields may not correspond. For example, if the Commodity field shows "niobium; rare-earth elements; thorium; uranium; zirconium", the Value_Mat field may list the associated ore minerals in a different order. The data in lists are alphabetized to prevent duplication of values as authors compile the dataset, with individual values separated by semicolons. 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. Additionally, values in the fields Commodity, and Material, may be lumped into groups such as rare-earth elements (REE), rare-earth oxide (REO), or total rare-earth oxide (TREO). For the purpose of the USMIN dataset, the rare-earth elements include the commodities cerium (Ce), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), holmium (Ho), lanthanum (La), lutetium (Lu), neodymium (Nd), praseodymium (Pr), promethium (Pm), samarium (Sm), terbium (Tb), thulium (Tb), and ytterbium (Yb) .
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, and the report also provides production data for underground "Mine X" that is associated with 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 feature classes and tables 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 that the attribute field Mat_Amnt occurs in the Production table and in the Resources table.
