The Esri ArcGIS 10.5 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 and prospects), 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. In this database, all mineral regions are mining districts.
The Loc_Poly feature class contains footprints or polygons of areas, deposits, mineral districts, mining 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 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 “chalcopyrite”, and another reports "chalcocite and bornite", 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, Fournier (1967). 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. If resources or reserves are reported for a group of features rather than an individual deposit, for example, the Copper Creek deposits, 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. For consistency, resource values are converted to International System of Units (SI) units by the USGS authors. Where 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 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. For consistency, production values are converted to International System of Units (SI) units by the USGS authors. Where 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 publically 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 1920 and 1992 respectively, the mine was active from 1920 to 1992; 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. If a deposit model classification 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, and 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 that is used throughout the database.
GENERAL INFORMATION
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 and prospects 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. Mineral showings, or the occurrence of potentially valuable minerals as indicated by geological examination or analyses of samples, are not included in the database.
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, such as gold or silver in the example of the Carlin area deposits. Mining district 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, “Outline of ore”, “Block model of 0.01 to 0.5 percent copper”, or “Boundary of mining district”).
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 publically 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 used as an identification (ID) in the database. In each feature class and table, the primary reference is noted in the Ref_ID field. Auxiliary references are enumerated after attribute field values, and the corresponding short reference is in the Remarks field. For example, the Commodity field shows “copper; rhenium (1)”. This indicates the commodity “copper” was derived from the primary reference denoted in the Ref_ID field as “Browne and Miller (2002)” and “rhenium” was derived from a secondary reference denoted in the Remarks field as “(1) John and Taylor (2016)”.
Attribute records that are blank, or contain a "Null" value in the file geodatabase, were checked for available data, and no data were found. Some fields have all blank values if the authors were unable to locate relevant published information. These blank 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.
