FULLER’S EARTH is clay or silty clay material that contains very fine
silica. It is soft, nonplastic, opaque, has a greasy feel when wet, and
does not readily break up in water. Its color varies from blue-gray to
yellow or buff.
Fuller’s earth is valuable for its unique property of absorbing and
decolorizing substances. The material was first used to “full” or remove
grease from woolen cloth, hence its name. It also has been used to
filter and bleach mineral and vegetable oils by absorbing dark organic
matter.
In Pulaski County in extreme southern Illinois the Porter’s Creek
Formation contains deposits of clay that were at one time the source of
fuller’s earth and still afford clay whose absorbent properties make it
useful as litter and as sweeping and cleaning compound.