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Show t FARMIN6 ABOVE AND ; MIR UNDERNEATH 5urvey Issues Report on Zinc-lead Mines of Illinois. Tn the popular mind most metal mining Is associated with mountainous regions. We know that coal is mined near corn-I corn-I fields, but how many, off-hand, would locate lead and zinc deposits in grain i fields? A recent publication by the ; United States geological survey describes a thickly settled agricultural district in northwestern Illinois where corn, oats, ji and hay are raised on the surface and ! lead and zinc are extracted from the ! rocks beneath the fields. ' ! The publication referred to is one of i" the units of the great geologic atlas of ti the United States and describes the Gall Ga-ll 'lena and Elizabeth quadrangles, in 1111-i' 1111-i' nois. The field surveys for this report ;' were made under the co-operative agree-ment agree-ment hetween the United States geologi-1 geologi-1 cal survev and the Stale of Illinois. Eu-!; Eu-!; gene "Wesley Sbaw and Arthur C. Trowbridge Trow-bridge are the authors. The area described de-scribed lies in the extreme northwest corner of tho state and is In the "drlft-. "drlft-. i loss area." which was not covered by the continental glacier and therefore con-i con-i tains no glacial drift. The exposed rocks are wholly of sedimentarv origin and con-; con-; sist of hard rock of Ordovician and Silurian age and unconsolidated surficial J deposits. The report describes these i rocks, shows the geologic structure or lay of the rocks, and gives the sequence j of events in the geologic history of the , ;; area and an account of' the mineral re-' re-' sources. Although agriculture is the principal industry, several hundred men are en-; ! payed in zinc and lead mining. The most 1 productive mines are grouped in certain rather small districts known as the Galena, Ga-lena, the Sand Prairie and the Elizabeth districts. The productive ore bodies are confined to the Galena dolomite and the recorah shale. Most of the mines are 100 to 200 feet deep. The production of' lead concentrates in 1914 was valued at , ?2S.7S8, and that of zinc concentrates at . $320,012. The lead sold from this region re-gion since mining began has brought about $50. 000.000, and the zinc produced since about I860 has been sold for about 510. 000. 000. Prospecting for new deposits still continues. The folio contains geologic and topo-; topo-; graphic maps and a map showing geologic geolo-gic structure, besides fourteen large pages of text. The Galena and Elizabeth folio (No. 200) is sold by the United States Geological Geo-logical Survey, "Washington, D. C., at 25 cents a copy. |