I called the Fresh Step (Clorox Corp) toll-free number to complain about the dust in their cat litter and to ask about the silica (carcinogenic to mice) content, and I was informed by their consumer rep. that all clay litter brands, whether clumping or non-clumping, contain silica, a naturally occurring mineral.
The crystal form cat litter contains silica-crystalline, a man-made material, and entirely different from silica.
No matter what bag of Fresh Step I buy (I try to select the freshest, best looking bags), I still get plenty of clay dust while dumping the litter into the litter box and while scooping before the kittens have used the fresh litter for several days. Cindy and Lucy share the same litter box and Punky has her own.
I use non-clumping litter because the animal shelter recommended it for kittens and specifically, they recommended Fresh Step. Clumping litter can be dangerous for kittens.
I'll ask the vet about when I can switch to the clumping form of litter, but I intend to try the natural litter like Feline Pine and Yesterday's News first.
With Fresh Step premium clay, you can scoop down into the box where the cats pee, and that keeps the litter from clumping on the bottom of the litter box. Cleaning's easy except for the dust when you dump the litter into a bag. I dislike the idea of depositing all of that used clay litter into the trash and wherever the trash companies dump it.
In addition, I was really disappointed that Fresh Step didn't offer to send me any coupons or special offers after I called their toll-free number.