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
Our Hoosier State Beneath Us: