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: