I've known quite a while that clay cat litter comes from strip mining. Not good. Not good at all. But I was of the mistaken understanding that my cats wouldn't tolerate a shift to a less destructive litter. Not so. I've been using a clumping litter made of grass for the last month. I put it under the clay litter at first so the cats would mix it themselves but I've had not complaints and no thinking outside the box. It's a bit more expensive but the earth is so worth it. Here's an article on alternatives if you're ready to help out in this effort.