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(Pocket-lint) - Speculation has begun about Apple's new factory in Arizona that we reported on last week. For the project, Apple has linked with GT Advanced Technologies  - a company that focuses on sapphire crystal -  and will be capable of manufacturing 5-inch screen covers for 33.79-50.56 million iPhones a year, according to Digitimes.

Apple has confirmed $578 million of sapphire glass, also used on the iPhone's camera and fingerprint sensor, will be made at the factory. The company hasn't confirmed what the intended use of sapphire glass will be. If Apple chose to use sapphire inside the iPhone's screen, it would be ditching Corning's Gorilla Glass, another US-based company which covers the screens of many manufacturers worldwide.

According to TechCrunch, which has done a lot of research into Apple's use of sapphire, it would offer many benefits over Gorilla Glass. Sapphire not only has better scratch resistance, but also better optical qualities, hardness, strength and toughness.

Digitimes's claims for a 5-inch display are echoed in its latest report. This matches nicely with what we've heard in the past regarding Apple's 5-inch+ iPhone plans for 2014. Digitimes has had a mixed track record in the past, but its positive reports have come out of the supply chain specifically. At any rate, the figures should help provide some estimates surrounding how massive the factory is.

Apart from iPhone displays, industry insiders have also speculated the factory will be responsible for iWatch displays.

Writing by Jake Smith. Originally published on 11 November 2013.