Feline Pine clumping litter has NO silica in it. It uses Guar Gum to "clump" the litter. I've used this brand, and I read the label. Guar gum is (to quote a website) is "a white flour-like substance used as thickener, binder, and volume enhancer". It's used in human food, even ice cream, to help bind some of the ingredients. It's totally safe. Any ingested litter dust will either be digested or will pass through the cat's system.
The litter actually more clings together than technically clumps. I don't know how solid the clump is when it dries, as I'm always cleaning the box out before the damp litter dries.
"That house is doubly blest / Which to our feline friends gives rest." (The Black Cat, 1941 movie)