The iPhone display is covered by Corning’s Gorilla Glass (not sapphire). The iPhone 4S’ TouchID sensor (the home button) is covered by a small synthetic sapphire pane. However, given Apple’s substantial investment in GT Advanced, the company might use sapphire for larger panes in the future.

http://www.macrumors.com/2013/11/04/apple-to-build-new-700-e...

http://www.macrumors.com/2013/11/12/apples-new-manufacturing...