In general, cat experts are not fond of crystal cat litters that are made out of dried silica gel. However, these kitty litters are popular with some cat owners for a very understandable reason: A single serving of crystals can last in a litter box for an entire month, thanks to the super-absorbency of sodium silicate, the same material that is packed into pill bottles to keep their contents dry. (Of course, this only applies to cat urine; you still have to scoop out your cat's solid waste every day.) Because they don't have to be changed as often as clay or biodegradable litters, crystal cat litters come in more manageable bag sizes (as small as 4 pounds), a big plus for cat owners who are unable to do heavy lifting.
However, as convenient as crystal litters can be for people, cats are likely to see things from a different perspective. The tiny, jagged crystalline particles can be very hard on a cat's sensitive paws. Even if your cat consents to using a crystal litter, it may not be very happy about it. There's also a downside from the human perspective: Once a portion of crystal litter has reached its absorbency limit, you'll end up with a pool of urine in the box.
That said, the same rule applies to crystal cat litters as to fine-grained clumping clay litters: Because they're all made from pretty much the same ingredients, there's not much difference among individual brands. Although no crystal litter receives more than one pick in the Our Sources section of our report, Pestell Clear Choice Low Track Silica Crystals Cat Litter (*Est. $21 for 12 lbs.) is included in ConsumerSearch Best Reviewed. Christie Keith at the San Francisco Chronicle says that it controls odor well, but that the texture bothers some cats. She adds that it's "the most costly cat litter ever made."
Although we haven't included any of these formulations in the ConsumerSearch Best Reviewed section because there aren't a sufficient number of reviews, you should bear in mind that some manufacturers (such as the makers of Scoop Away, Tidy Cats and Ever Clean) offer clumping clay/crystal blends that combine the clumping action of fine-grained clay with the super-absorbency of crystals. If you're searching for the perfect litter for your cat, it may be worth buying a small bag to see how well it works for you.