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Person

Albert H Hofstra

Research Geologist

Geology, Geophysics, and Geochemistry Science Center

Email: ahofstra@usgs.gov
Office Phone: 303-236-5530
Fax: 303-236-3200
ORCID: 0000-0002-2450-1593

Location
Building 95
P.O. Box 25585
Denver Federal Center
Lakewood , CO 80225-0585
USA

Supervisor: Andrew G Hunt
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The Critical Minerals in Archived Mine Samples Database (CMDB) contains chemistry and geologic information for historic ore and ore-related rock samples from mineral deposits in the United States. In addition, the database contains samples from archetypal deposits from 27 other countries in North America, South America, Asia, Africa and Europe. Samples were obtained from archived ore collections under the U.S. Geological Survey's project titled "Quick Assessment of Rare and Critical Metals in Ore Deposits: A National Assessment" (2008 to 2013) in an effort to begin an assessment of the Nations' previously mined ore deposits for critical minerals. Mineralized and altered rock samples were provided by the Colorado...
Categories: Data; Types: ArcGIS REST Map Service, ArcGIS Service Definition, Downloadable, Map Service, OGC WFS Layer, OGC WMS Layer, Shapefile; Tags: Alaska, Argentina, Arizona, Arkansas, Australia, All tags...
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Twenty-five ore and gangue mineral separates from the Miocene-age Goldfield and Tonopah epithermal Au-Ag deposits in southwestern Nevada were analyzed to determine the helium, neon, and argon (He, Ne, and Ar) isotopic compositions contained in fluid inclusions. Four mineral separates from the Butte Main Stage vein deposit and two from the Bingham pyrite-enargite vein deposits were also analyzed. Fifteen separates are from hand samples collected from underground mine workings and the remaining 16 are from mine tailings piles and pits excavated within the past 100 years. The separates consist dominantly of pyrite, enargite, and quartz, with lesser amounts of sphalerite, galena, potassium feldspar, bismuthinite, marcasite,...
Categories: Data; Tags: 3He/4He, Ar, Bingham Copper Mine, Bingham pyrite-enargite vein deposit, Butte Main Stage vein deposit, All tags...
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Multispectral remote sensing data acquired by Landsat 8 Operational Land Imager (OLI) sensor were analyzed using an automated technique to generate surficial mineralogy and vegetation maps of the conterminous western United States. Six spectral indices (e.g. band-ratios), highlighting distinct spectral absorptions, were developed to aid in the identification of mineral groups in exposed rocks, soils, mine waste rock, and mill tailings across the landscape. The data are centered on the western U.S. and cover portions of Texas, Oklahoma, Kansas, the Canada-U.S. border, and the Mexico-U.S. border during the summers of 2013 – 2014. Methods used to process the images and algorithms used to infer mineralogical composition...
Categories: Data, Data Release - In Progress; Types: ArcGIS REST Map Service, ArcGIS Service Definition, Downloadable, Map Service; Tags: Arizona, California, Canada, Colorado, Idaho, All tags...
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Multispectral remote sensing data acquired by the Landsat 8 Operational Land Imager (OLI) sensor were analyzed using a new, automated technique to generate a map of exposed mineral and vegetation groups in the western San Juan Mountains, Colorado and the Four Corners Region of the United States (Rockwell and others, 2021). Spectral index (e.g. band-ratio) results were combined into displayed mineral and vegetation groups using Boolean algebra. New analysis logic has been implemented to exploit the coastal aerosol band in Landsat 8 OLI data and identify concentrations of iron sulfate minerals. These results may indicate the presence of near-surface pyrite, which can be a potential non-point source of acid rock drainage....
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This data release presents geochemical analyses of silicate melt inclusions, host quartz phenocrysts, and biotite phenocrysts in samples collected by the U.S. Geological Survey (USGS) from mid-Cenozoic rhyolitic rocks from northern Nevada. Igneous intrusions and volcanic rocks in this study encompass nineteen rhyolitic samples from five magmatic centers across northeastern Nevada. Rhyolites were emplaced throughout northeastern Nevada over about an 8 million year timespan (41–33 mega-annum) in a variety of eruptive styles and volumes, ranging from meter-wide dikes to caldera-forming ignimbrites, and were roughly contemporaneous with regional ore deposition. Samples were prepared for petrographic and scanning electron...
Categories: Data; Tags: Bald Mountain, Beast pit, Blue Star Mine, Caetano Caldera, Carico Lake Valley, All tags...
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