Subject
Geology
Gold mines and mining
Mines and mineral resources
16
Water-supply
6
Coal mines and mining
4
Paleontology
4
Coal
3
Gold ores
3
Petrology
3
Placer deposits
3
Alaska
2
Coal Testing
2
Copper mines and mining
2
Geology, Economic
2
Igneous rocks
2
Mineral industries
2
Ore deposits
2
Sedimentation and deposition
2
Seward Peninsula (Alaska)
2
Triangulation
2
Artesian wells
1
Briquets (Fuel)
1
Brooks Range (Alaska)
1
Cascade Range
1
Coal Geology
1
Fluorspar
1
Gold Assaying
1
Gypsum
1
Indian Territory
1
Indians of North America
1
Lead ores
1
Limestone
1
Mathematical geography
1
Mineralogy
1
New York (State) Altitudes
1
Nome Region (Alaska)
1
Ohio Altitudes
1
Oil fields
1
Peat
1
Pennsylvania Altitudes
1
Petroleum
1
Slate
1
Stratigraphic correlation
1
Tellurides
1
Veins (Geology)
1
West Virginia
1
Zinc ores
1