Sapphire--it's not just for jewelry anymore. In the last few years, Apple has increased its use of the material in its products, and that trend seems to be on the upswing. On Monday, Arizona governor Jan Brewer announced that Apple will open a manufacturing facility in Mesa; that plant will be operated by GT Advanced Technologies, which will be providing sapphire for Cupertino's products.

The plant will employ 700 workers and seems positioned to provide a lot of sapphire. Currently, Apple uses the material in relatively few places: It covers the lens on the iPhone 5c and 5s and is used as the top layer in the Touch ID sensor on the iPhone 5s. In both cases, it's harder and provides much more scratch resistance than conventional glass.

By investing in a facility designed for the production of sapphire, though, it seems possible that Apple's expecting to need more of the material than it would require simply to make lens covers. Daring Fireball's John Gruber speculates that Apple may actually plan to use the factory to produce sapphire glass displays for its devices; earlier this year, a report suggested that Apple had already begun to investigate the possibility, though doing so in the necessary volume had proved challenging.

The Arizona plant also moves Apple towards another one of its goals: bringing more manufacturing jobs back into the U.S. In the past, the company had come under fire for its heavy reliance upon overseas firms like China's Foxconn, which itself had been criticized for its lack of worker protections. Last December, Apple CEO Tim Cook announced that Apple would move some Mac production back into the United States; the revamped Mac Pro, which will be released later this year, is the first new Mac to be assembled domestically.

As with Apple's other recent facilities, such as its data centers in Oregon and South Carolina, the Arizona facility will rely on 100-percent renewable energy.