Cats generally prefer unscented, clay-clumping litter to silica gel and other types of litter because the clay texture is most similar to sand or dirt—which is what your cat’s wildcat ancestors have used for tens of thousands of years (and where your cat’s biological instinct to bury waste stems from)! Furthermore, silica gel litter typically contains added chemicals and perfumes because its clumping and odor-absorbing capabilities are minimal compared to clay litter.