Revisiting interactive geochemical & mineralogic maps for soils of U.S.

Copper in soil at 0-5 cm depth

From 2007 to 2010, the U.S. Geological Survey collected soil samples from 4,857 sites throughout the conterminous United States to support the North American Soil Geochemical Landscapes Project.

Hematite (iron oxide) in A Horizon, note enrichment in AZ

The objective was to provide background data for, 'Understanding the variability in the natural abundance and spatial distribution of chemical elements (geochemical background) in the near-surface environment of the Earth is important for such fields as risk-based assessment of contaminated land, environmental regulation, human and animal health, agriculture, land-use planning, mineral exploration, and water quality. Geochemical mapping, conducted at appropriate scales, is the primary method for establishing this variability.' 

To access the interactive soil chemistry map: https://mrdata.usgs.gov/soilgeochemistry/#/periodictable

To access the interactive soil mineralogy map: https://mrdata.usgs.gov/soilgeochemistry/#/mineralogy

USGS Soil Chemistry and Mineralogy publication: https://pubs.usgs.gov/of/2014/1082/pdf/ofr2014-1082.pdf