He says that the glass on the front and back is "scratch-resistant aluminosilicate glass," and the metal around the edges is one full band of stainless steel. (The "seams" are just cosmetic -- it's all one piece, apparently.) "That understanding, that preoccupation with the materials and processes," Ive says, "is essential to the way we work."
Ive does have his usual ethereal lightness about how hard design is to grasp. "You cannot disconnect the form from the material -- the material informs the form," he says. If nothing else, though, the interview definitely shows just how obsessive he and Apple are about designing and manufacturing these devices.
iPhones become commonplace so quickly after launch that you tend to forget all of the work and thought that has gone into every single feature of their hardware. Apple isn't really doing anything magical here; it's just sitting down and grinding out exactly what materials work best in which ways in order to make a really beautiful and functional object.