Underclay: A once-important Hoosier mineral resource (IM-09)
Underclay contains substantial amounts of the mineral kaolinite, form which temperature-resistant ceramic ware can be made. Underclay provided raw material for a once-thriving clay-products industry in Indiana, but only remnants of this activity survive near Brazil. As coal mining increases and transportation costs rise, it may again become an important ceramic raw material because of its association with coal for fuel.
Our Hoosier State Beneath Us: Industrial Minerals