TRIPOLI, called amorphous silica in southern Illinois, is a white or
light brown, powdery substance that rubs off on the hands like chalk. It
consists mostly of very small particles of quartz that result from the
weathering of calcareous chert or highly siliceous limestone.
It is finely ground and used as “white rouge” for polishing optical
lenses, as a filler in paints, in making ceramic products, as a
component of buffing compounds, and as a fine abrasive.
Tripoli occurs in Alexander and Union Counties and is milled at Elco and
Tamms in Alexander County.