Baking Stones

My parents have a surplus of ceramic stones that they used when they were putting down their new kitchen floor. I'm also looking for baking stones to use and I figured these might be good choices. The box says they are ceramic but does not indicate whether they are glazed or unglazed although to my eyes they look matte and unglazed. Googling the company that made them yields no results. Can anybody share their thoughts about using these tiles??