I'm pretty sure a Sam Vimes reference can be had from this somewhere...

I started using Swheat Scoop kitty litter in my cats' litterbox recently. It clumps, it's made from wheat, it doesn't have weird chemical smells as part of its masking efforts, and I can flush it. The litterbox is an automatic model that sweeps through with a rake ten minutes after the cat gets out of the box. The rake leaves neat little evenly spaced lines across the surface of the litter. Sometimes if one cat uses the box, the next one to come along doesn't bother burying his doots, or even disturbing the surface much; it's pretty standard 'whozyerdaddy' behaviour in the animal kingdom.

Thing is, with poo on the surface and the lines still visible in the litter... well, the litter is a sort of pale tannish colour. It looks rather like sand, only with oversized particles.

Kind of the world's most biological Zen rock garden.