All clumping litters are made from sodium bentonite, a form of clay. Premium scoopables, like HAPPY CAT uses 100% sodium bentonite to maximize clumping. Some clumping litters blend cheaper clayes with bentonite and will break apart in the litter box.
Short column, ball granularity or no finalize shape, non-dissolvable in any solution, non-poisonous, is strongly water-absorbent.