The basic answer is that only people at Apple and Corning know for sure if Gorilla Glass is part of the iPad line of products. While Corning lists several manufacturers as clients on its Gorilla Glass Web page, you won't find Apple among the names. But that doesn't mean Corning and Apple aren't doing business together.
Corning only shares information about its clients with their permission. Should a company wish to keep its components secret -- a practice for which Apple is famous -- Corning won't list its name on the Gorilla Glass site. Just because Apple is nowhere to be found on the site isn't enough evidence to draw conclusions.
Asking Apple or Corning doesn't seem to help, either. Inquiries tend to be ignored or, if you're lucky, answered with a simple "no comment." Getting an official, straight answer from either party appears to be a dead end.
To complicate matters, there are other companies that produce aluminosilicate glass. One candidate is a Japanese company called Asahi Glass Company. In 2011, Asahi introduced a new product it calls Dragontrail Glass. Said to be six times stronger than standard glass, this product resists scratches and breaks in a way similar to Corning's product.
Many of the parts you'll find in Apple products come from Asia. Could the glass for iPad screens be among them? Since neither Apple nor Corning will own up, the matter remains unresolved for the rest of us. We can only draw conclusions on circumstantial evidence while we wait for someone in charge to spill the beans.
