Indianite: Hoosier Rock with a Past (IM-01)
About 1870, State Geologist E.T. Cox gave the name indianite to a unique mixture of clay minerals found in south-central Indiana. Composed of the minerals halloysite, kaolinite, illite, and gibbsite, indianaite is a very fine grained and relatively soft rock occurring in small, irregular pods or lenses mainly in Lawrence and Martin Counties and southern Monroe County. It is white when pure, but impurities - mainly iron - cause the material to be reddish brown.

Indianite was mined mainly from 1870 to the 1890's and shipped as far as Philadelphia. Much was used in manufacturing white porcelain, but large quantities were combined with sulfuric acid to make alum. During World War I, some indianite was used in making refractory brick, and in the 1920's some was mined as an aluminum ore. But indianite is no longer mined.

Our Hoosier State Beneath Us: Industrial Minerals