Hello, this is probably a silly question, but I went down to Lowe's earlier today to find some unglazed quarry tiles, and I found some with the brand name versaTILE. On the box, it said something about containing .1% silica or something, and that if the tile breaks, the dust could cause problems to the lung or something. Is this typical of unglazed quarry tiles? I thought that unglazed quarry tiles were pretty much the same despite the brand, but I guess I could be wrong. So I asked a worker if they were ok to cook on, and he told me that unglazed quarry tiles were terrible for holding heat, which I thought was definitely wrong, but now I am befuddled. Any answers would be greatly appreciated!