For those who were asking about cheap unglazed clay tiles that you
can use as a pizza stone in the oven:

It's called a Saltillo paver. 12 x 12 inches. $1.19
The Home Depot item number is 187-565.
http://i49.tinypic.com/r77w5y.jpg

The one I bought for a pizza stone is nice and flat. When I went
back yesterday, every one they had in stock had some kind of animal
tracks in the surface. Not just one kind, either, but quite a
variety of tracks.