Im getting desperate.
Is there any danger in using a tile that youre not sure is food safe but using parchment as a barrier between the bread and stone?
Perhaps. None of us are going to be able to totally set your mind at ease or indemnify you from health risks.
That said, I've done it more than a few times. I'm not dead yet.
So do it at your own peril.
Most of the health concerns are probably not that serious. What I am getting at is the fact that when most of our grandparents grew up there were probably a whole lot fewer of these over concerned health advices. And many of them did still live to 80-90 years of age.
The biggest problem in our age is worrying to much about small things. What really kills you is cars, cigarettes, alcohol, fatness from over eating etc. not the trace amounts of lead you might find on your baking stone. And if you still are concerned just put a sheet of parchment in between you loaf and the stone.
I worked for 5 years for one of the world's largest industrial refractory manufacturers. I would strongly advise against using any refractory for cooking unless it has an MSDS or similar documentation stating that is is food safe. Although I cannot violate confidentiality on the components or manufacturing processes I _can_ tell you that we had strict separation between our industrial refractory processes and our medical/laboratory processes - and for very good reason.
Sometimes there are wolves in the woods. Even if saying so is considered "politically correct".
i just bought some 12x12 saltillo tiles at homedepot, but none of my local home depots will cut them! they all say they used to do that but not anymore. without cutting, all i can fit is 1 tile in my oven. ugh...