the cretaceous age, volcanoes in the Yellowstone area of
Wyoming were subject to long periods of eruptions. Ash
falling from these eruptions dropped into seas which
covered much of Wyoming, forming a sediment as much as
50 foot deep. These sediments were slowly altered into
the clay we know today as bentonite. In these deposits
are contained 70% of the world's known supply of western
or sodium montmorillonite.