Strip mining removes the top layers of rock and soil with large pieces of machinary - essentially destroying that land. This is how we get our traditional cat litter! They detroy land so we can scoop out our cat's crap.

There are a few healthy alternatives to cat litter out there. I'm using one, but another that has gotten good review is this pine one.

It's all natural and biodegradable (and 100% renewable).
Available online or at PetSmart.

My 15 year old cat loves this pine litter and so do I. The litter box doesn't smell like it can with clay litters and she doesn't track it all over the place like clay litter. You use much less litter in the long run too.