Prospect- and mine-related map features: Symbols indicating mining-related features digitized from historical USGS topographic maps, includes prospect pits, mine shafts and adits, quarries, open-pit mines, gravel and borrow pits.
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Mining activity is shown on historical topographic maps made by the USGS during the last half of the 20th century. The map symbols indicate the type of geographic feature (mine shaft, adit, prospect pit, open pit, and so on) and some are labeled with the feature's name. Since topographic maps were revised every decade or so, these symbols may indicate not only the extent of mining activity but also its history, where the activity occurred during the decades in which the maps were revised.
Need more? You can View, Download, and Understand this data source at https://MRData.usgs.gov/usmin/.
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