There Are Different Types Of Bentonite, Each Named After The Respective Dominant Element, Such As Potassium ( K) , Sodium ( Na) , Calcium ( Ca) , And Aluminium ( Al) . Experts Debate A Number Of Nomenclatorial Problems With The Classification Of Bentonite Clays. Bentonite Usually Forms From Weathering Of Volcanic Ash, Most Often In The Presence Of Water.