I'm not sure what it is made of either, but I doubt it is Gorilla Glass. I've got one smallish scratch that you can feel with your fingernail and lots of little scratches you can see when the light hits it right. And the phone is barely two weeks old. Of course, it sits on the back all the time so it's more likely to pick up scratches than the front but it should be tougher than that.
That and the slipperiness of it is why I am reluctantly getting a case, the thinnest one I can find.