The project with GT Advanced, dubbed Operation Cascade, involves GT operating equipment it purchased, inside Apple's facility in Mesa. Apple has pre-paid GT Advanced $578 million which will be repaid over 5 years, starting next year. Foxconn has allegedly produced 100 prototypes of the next-gen Apple iPhone using a sapphire glass cover, just to test the manufacturing process. As the second hardest material after diamonds, a sapphire glass display for the Apple iPhone would be more resistant to scratching and cracking than Corning's Gorilla Glass. The facility in Mesa is expected to begin operation next month.
Apple currently uses the material as a lens cover on the Apple iPhone 5s, and to protect the fingerprint scanner on the TouchID embedded in the home button on the flagship model. Besides the possibility of Apple using more of the material on the next-gen iPhone, there is speculation that it will be used to produce the screen for the rumored Apple iWatch.
source: Scribd, 9to5Mac via AppleInsider