Well From what i can gather so far from the net bentonite is fullers
earth and is the chief constituent in cat litter and speedi dry
(industrial absorbent).
I assume fine sand ie silver sand or childs playsand as we call it in
this country can be mixed with crushed cat litter and a little water
to make a form of casting sand.
I wander how many Females realize that fullers earth (used as a
cleansing cream by women worldwide) is really crushed Kats litter ! The
mind boggles