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Geology and zinc-lead deposits in the Couler Valley area, Dubuque County, Iowa Geology and zinc-lead deposits in the Couler Valley area, Dubuque County, Iowa
Geologic investigations were begun in the Iowa portion of the Wisconsin-Illinois-Iowa zinc-lead district to appraise its potentialities: (1) for zinc ore in strata that elsewhere in the mining district contain large zinc ore bodies and (2) for lead and zinc deposits of the type that were mined extensively in Dubuque County, Iowa, during the 19th century.
Geology and zinc-lead deposits in the Durango area, Dubuque County, Iowa Geology and zinc-lead deposits in the Durango area, Dubuque County, Iowa
Geologic investigations were begun in Iowa to appraise; (1) the possible occurrence of zinc ore in strata that elsewhere in the Upper Mississippi Valley zinc-lead district have been the principal sites of zinc concentration; and (2) lead ore of the type known as "crevice deposits," which were mined so extensively during the 19th century in Dubuque County, Iowa, but have been mined very...