Marl (IM-04)
Marl has had a special importance to northern Indiana since John Leslie and Thomas and Duane Millen built a portland cement plant at South Bend in 1877. It was the second portland cement plant in the United States and the first ever to use marl as a raw material. Prior to that time pioneers had used marl as a flux in making iron and had burned it to make lime for mortar. Today, marl is used only as agricultural lime, a soil conditioner.

Marl is mud which contains 50 to 90 percent lime precipitated mainly by plants and is found in the bottoms of small lakes in northern Indiana. Close inspection of marl reveals fragments and whole shells of snails, small clams, and other organisms together with clay and remains to aquatic plants.

Our Hoosier State Beneath Us: Industrial Minerals