Sapphire crystal growth solutions provider GT Advanced Technologies announced earlier this week that it inked a big deal with Apple. The company said that Apple will prepay for about $578 million worth of sapphire growth equipment that will be used in the company’s facilities in Arizona. But what is Apple going to do with all that crystal? There has been some speculation that future iPhone handsets will feature sapphire display covers in place of what some presume to be Corning Gorilla Glass Apple currently uses, and Digitimes’ research arm apparently subscribes to that theory. Unfortunately, the group’s own math likely disproves the notion fairly conclusively.