Identification_Information: Citation: Citation_Information: Originator: U.S. Geological Survey Cooperating agencies: Bureau of Land Management and U.S. Forest Service Author or compiler: Bradley S. Van Gosen, Jane M. Hammarstrom, Karl S. Kellogg, and Richard B. Berg Publication_Date: 1998 Title: Map showing areas with potential for garnet resources in bedrock and placer in the Blacktail Mountains and the Gravelly, Greenhorn, Ruby, and Snowcrest Ranges of southwestern Montana Series_Information: Series_Name: U.S. Geological Survey Open-File Report Issue_Identification: OF 98-224-A Publication_Information: Publication_Place: Denver, Colorado Publisher: U.S. Geological Survey Online_Linkage: http://greenwood.cr.usgs.gov/pub/open-file-reports/ofr-98-0224-a Description: Abstract: Garnet crystals, some of gem quality, have been sought by rock hounds for many years in the alluvial deposits of the Alder Gulch-Ruby River area. Since 1995, garnet has been extracted from these gravels for industrial products at two separately owned placer mines in the region: (1) at Cominco American's "Ruby Garnet" operation at Alder, Montana, and (2) at the "Sweetwater Garnet" operation in the Sweetwater Basin of the Ruby Range. The two placer mines excavate different types of garnetiferous deposits, but both produce sized concentrates of almandine garnet derived from similar source rocks. At Cominco American's Ruby Garnet placer mine, the garnet is removed from 1920's gold dredge tailings, up to 15 m thick, in Alder Gulch near Alder. The dredged alluvial material at Alder typically contains from about 4 to 10 percent garnet, mainly the almandine variety. The Ruby Garnet operation separates on site the free grains of garnet from the tailings using a series of gravity separation processes. The garnet concentrates are separated into several size fractions and sold accordingly for use in light grinding, sand blasting, abrasive water-jet cutting, and filter bed material in water purification plants. This placer mine received its permit to operate in 1993. In 1996 the Sweetwater Garnet placer mine began production in the central Ruby Range. This mine recovers almandine garnet from alluvial deposits located about 0.8 km north of the main road in the Sweetwater Basin, about 22 km east-southeast of Dillon, Montana (section 17, T.8S., R.6W.). The processing plant for the operation is located at the Barretts exit of interstate highway 15, about 10.5 km southwest of Dillon. The garnetiferous sediments excavated by this placer mine are thin deposits of stream-worked material derived from the surrounding bedrock of Archean quartzofeldspathic gneiss. This garnet-bearing alluvium fills the narrow stream beds that drain into the Sweetwater Basin. Alluvial fans and eluvial deposits throughout the Sweetwater Basin are prospective for garnet concentrations. The virgin alluvial gravels of the Ruby River valley and alluvial fans along the mountain fronts also hold plentiful deposits of garnet. For many years, mineral collectors have retrieved garnets from the gravels in Barton Gulch, which drains into Ruby Reservoir from the northwestern part of the Greenhorn Range. This map shows garnetiferous bedrocks and proximal deposits of alluvium for a large area of southwestern Montana, an area chosen for evaluation by the Bureau of Land Management and U.S. Forest Service. The map was prepared as part of a mineral resource assessment of specified areas in Beaverhead and Madison Counties, Montana, which contain federally-managed lands. Purpose: The Bureau of Land Management and U.S. Forest Service use mineral resource data in developing land-use management plans for the reasonably foreseeable future. Supplemental_Information: Map political location: Beaverhead and Madison Counties, Montana Compilation scale: 1:250000 Geology compiled in 1997 and 1998; compilation completed 4/98. Review and revision completed 5/98. Paper copy published as Open-File Report 98-224-A Web version (.pdf) released on 12/03/98 ARC/INFO archive files prepared 12/98. Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 19981203 Currentness_Reference: Published in 1998 Status: Progress: Complete. Maintenance_and_Update_Frequency: None. Mapping is continuing in adjacent areas for different purposes. Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate:-113.0 East_Bounding_Coordinate:-111.25 North_Bounding_Coordinate: 45.75 South_Bounding_Coordinate: 44.5 Keywords: Theme: Theme_Keyword_Thesaurus: Geology Theme_Keyword: Geologic map Theme_Keyword: Garnet Theme_Keyword: Mineral resource Theme_Keyword: Placer Place: Place_Keyword_Thesaurus: none Place_Keyword: Montana Place_Keyword: Blacktail Mountains Place_Keyword: Gravelly Range Place_Keyword: Greenhorn Range Place_Keyword: Ruby Range Place_Keyword: Snowcrest Range Place_Keyword: Beaverhead County, Montana Place_Keyword: Madison County, Montana Place_Keyword: Beaverhead National Forest, Montana Place_Keyword: Dillon Place_Keyword: Alder Access_Constraints: none Use_Constraints: None. Acknowledgment of the U.S. Geological Survey would be appreciated in products derived from these data. The map data were originally compiled and digitized at a scale of 1:250,000, and thus the data should be considered accurate only when used at that scale. Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: Data was entered and checked by the geologist who made the observations. Logical_Consistency_Report: Map elements were visually checked by the author for overshoots, undershoots, duplicate features, and other errors. This digital release is preliminary and has not been thoroughly reviewed for conformity with U.S. Geological Survey editorial standards or stratigraphic nomenclature. The paper copy (Open-File Report 98-224-A) was reviewed by one other geologist for consistency with basic geologic principles and general conformity to USGS mapping standards. Completeness_Report: This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or stratigraphic nomenclature. This ARC/INFO release is provided only to be used with the published Open-File Report 98-224-A (paper copy). The topographic base map used for the paper copy release was scanned and included as the base for the paper copy; this base is not currently available separately. Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: Lines were digitized from original source maps at their original scales and projections, then composited at the final scale and projection in GSMAP. Lineage: Process_Step: Process_Description: The geologic database was compiled using the GSMAP public domain program (USGS Open-File Report 93-511) and later upgraded to the Windows version of GSMAP-- GSMCAD public domain program (USGS Open-File Report 96-007). It was exported to ARC/INFO using the GSMCAD export function to create ARC/INFO generate files. The ARC/INFO generate files were reloaded into ARC/INFO programs and attributed to match the published map (Open-File Report 98-224-A). Process_Date: 12/02/98 10:00 AM Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: Vector Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Map_Projection: Map_Projection_Name: TRANSVERSE MERCATOR Transverse_Mercator: Scale_Factor_at_Central_Meridian: 0.9996 Longitude_of_Central_Meridian: -112.5 Latitude_of_Projection_Origin: 0.0 False_Easting: 0.0 False_Northing: 0.0 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: coordinate pair Coordinate_Representation: Abscissa_Resolution: 0.001 Ordinate_Resolution: 0.001 Planar_Distance_Units: METERS Geodetic_Model: Horizontal_Datum_Name: North American Datum of 1927 Ellipsoid_Name: Clarke 1866 Semi-major_Axis: 6378206.4 Denominator_of_Flattening_Ratio: 294.98 Entity_and_Attribute_Information: Overview_Description: Entity_and_Attribute_Overview: The data is supplied in two formats: 1. Adobe Acrobat 3.0 .pdf format 2. UNIX based ARC/INFO format DATABASE STRUCTURE - ARC/INFO ==================================== The database of the map consists of two coverages (root names = GARNET and GARNET_P) and three additional auxiliary files: GARNET.E00: ARC/INFO interchange file that can be used to create the geologic map shown on Open-File Report 98-224-A. GARNET_P.E00: ARC/INFO interchange file that can be used to create point files that display the locations of the two garnet placer mines shown on Open-File Report 98-224-A. Auxiliary files: GARNET.AML: ARCPLOT commands that create the geologic map of Open-File Report 98-224-A from the data bases. GARNET.COL: A look-up table of the polygon attributes in GARNET.E00. GARNET.PNT: A look-up table of the point attributes in GARNET_P.E00. Entity_and_Attribute_Detail_Citation: Database root name: GARNET P1 VALUE AND LETTER SYMBOLS FOR GEOLOGIC UNITS MAPPED======= CODE | FEATURE 1,Qa 2,O (other rock types) 3,Qf 22,Aqf 23,Aa 24,Asg 27,Ag 36,Qg 37,Qtb 38,Aam 39,Aag 40,Aq FEATURES IN THE DATABASE------------------------- CODE | FEATURE 010 | study area boundary 011 | map unit contact 300 | symbol (site of garnet placer mine) 500 | map unit label Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey, Mineral Resources Program Contact_Address: Bradley S. Van Gosen Address_Type: mailing address Address: U.S. Geological Survey Address: MS 905, Box 25046, Denver Federal Center City: Lakewood State_or_Province: CO Postal_Code: 80225-0046 Contact_Voice_Telephone: (303) 236-1566 office Contact_Voice_Telephone: (303) 236-1800 secretary (Joan Luce) Contact_Electronic_Mail_Address: bvangose@usgs.gov Distribution_Liability: Although this digital spatial data has been subjected to rigorous review and is substantially complete, it is released on the condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use. Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: ARC/INFO Format_Version_Number: Version 7.1.1 Format_Version_Date: 1997 File_Decompression_Technique: None Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address Network_Resource_Name: http://greenwood.cr.usgs.gov Fees: None Metadata_Reference_Information: Metadata_Date: 19981203 Metadata_Review_Date: 19981203 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Bradley S. Van Gosen Contact_Organization: U.S. Geological Survey, Mineral Resources Program Contact_Address: Address_Type: mailing address Address: U.S. Geological Survey Address: MS 905, Box 25046, Denver Federal Center City: Lakewood State_or_Province: CO Postal_Code: 80225-0046 Contact_Voice_Telephone: (303) 236-1566 office Contact_Voice_Telephone: (303) 236-1800 secretary (Joan Luce) Contact_Electronic_Mail_Address: bvangose@usgs.gov Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata Metadata_Standard_Version: 19940608