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- Geology393
- Geology, Stratigraphic93
- Mines and mineral resources24
- Iron ores22
- Paleontology15
- Groundwater14
- Botany11
- Copper mines and mining10
- Geography10
- Petrology10
- Description and travel9
- Glacial epoch9
- Iron mines and mining9
- MI9
- Precambrian Geologic Period9
- Zoology8
- Copper ores7
- Geological surveys7
- Indians of North America7
- Michigan7