IPhone=Optical Glass or Sapphire, what is it!!!?

my mom thinks its clear sapphire, i think so too because ive seen videos of people mutilating it with a key and no scratches at all, ive even tried “keying” it and no scratches, sapphire is one of the hardest its a 10 up with diamond, the only thing harder is diamond or its self can scratch it, so WHICH ONE IS IT optical glass or sapphire