Zinc and lead deposits of northwestern Illinois

Zinc and lead minerals are found in two widely separated districts in Illinois. One of these occurs in the extreme southern portion of the State and includes portions of Hardin, Pope, and Saline counties. It forms part of the Kentucky-Illinois fluorspar, lead, and zinc field, and for convenience may be referred to as the Southern Illinois district. The other occurs in the- extreme northwestern portion of the State and includes a part of Jo Daviess County. It is included in the upper Mississippi Valley zinc and lead field and may be conveniently referred to as the Northwestern Illinois district. This district forms the subject of this paper.