(iTers News) - Rumor has been around that Apple Inc. will use a slice of sapphire as a cover glass for a next generation of iPhones and iPads. It turns out to be true. Sapphire igot grower GT Advanced Technologies said today it has signed a deal with Apple Inc. to supply sapphire substrates.

Under the terms of the agreement, GT Advanced will operate its own advanced  sapphire furnace, or ASF at Apple’s Arizona facility to produce sapphire ingots, while Apple will pay US$578 million in advance to finance the operation. The prepaid US$578 million will be paid back over the 5 year period starting from 2015.

Apple will replace current Gorilla glass of Corning Inc. with the sapphire substrates use it as a protective cover for Retina panels in a new generation of iPhones and iPads.

Compared with Gorilla glass, the sapphire cover glass is much thinner, more resilient, stronger, and less susceptible to scratches, but is far costlier.

GT’s ASF is a platform for producing high-quality, large-size sapphire substrates to etch out high-brightness LED chips.  

GT Advanced Technologies is a maker of crystal growth equipment for solar cell and LED applications. Apple Inc  has used sapphire cover glass to protect iPhone's camera lens and iPhone 5S's home button