Lead and Zinc
Lead and zinc are the only metallic minerals mined in Illinois. Deposits are found in Jo Daviess County in northwestern Illinois and in the fluorspar area of Hardin and Pope Counties in extreme southern Illinois. In northwestern Illinois the ore occurs in rocks of Ordovician age, but in southeastern Illinois it is associated with fluorspar in rocks of Mississippian age.
Between 1820 and 1865, the mining area of which northwestern Illinois is a part was the nation’s principal producer of lead ore. In recent years production of zinc has increased and that of lead has decreased.