The general composit of most floors are alumina, SiO2, MgO, clay and some other elements, which are then pressed into tiles. For example the baking stone you see at williams sonoma or American Metal Craft is a low grade Cordierite material which has these elements.. You can also have the floor poured in a mold, by using materials by La Farge or Thermal Ceramics. La Farge makes a material called Fondag which is very hard and has high thermal shock, however it tends to be very dense and not too porous. Some of the economy wood fire ovens have a floor from a cast refractory.
If you need some of the tiles I have tons of them. I have 12 x 12 x 1 1/2. They do weigh 17 lb each so shipping can be expensive.