Silica powder is dangerous, so I would not expect anyone to make silica powder litter. Making it in the gel form keeps it bound, but if you crush it, it becomes like boric acid powder, and it can kill bugs that walk in it, like bedbugs and cockroaches. Your cat walks in the litter, and the dust would cling to his feet and hair. I would never use silica dust anywhere near my cat, so that could be why you can't find silica litter in a dust form.