Big Ten Academic Alliance Geospatial Discovery Portal
Big Ten Academic Alliance Geoportal
Map of Indiana showing locations of coal and industrial minerals operations
- Shaffer, Nelson R.
- Includes pie graph and list of further reading. '1984 (Modified 1997).' Scale 1:500,000 By Nelson R. Shaffer.
- Indiana Geological Survey
- Indiana Historic Maps
- Indiana, United States
- Mine maps
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- Visit Source