In other words, this seems like a long shot, at least for now.
iPhone 7 design rumours: Sapphire glass
Apple is already using sapphire in the display of the Apple Watch, and it's possible that the company is now ready to import this material into its smartphone lin-up. Sapphire glass is more durable than Gorilla Glass, so could be an ideal material to use for the bigger display.
Apple was backing a Sapphire plant in Arizona - run by GT Advanced Technologies - that could have been used to manufacture 200 million 5-inch iPhone displays per year, according to reports. But that company has now been declared bankrupt and was unable to meet Apple's demands.
There could be a further twist, however. New reports suggest that long-term Apple supplier Foxconn is gearing up to build its own sapphire plant in Asia, and could be able to take GT Advanced Technologies' place.
Foxconn's planned plant in Taiwan will cost it $2.6bn to set up, but could give it a huge advantage as companies jostle to be involved in the production of the next iPhone.
iPhone 7 design rumours: ...or super-hardened 'Project Phire' Gorilla Glass
Sapphire glass sounds nice, but don't write off Gorilla Glass (the material used on current iPhones) just yet.
Corning, the company that makes Gorilla Glass, has responded to the looming threat of Sapphire glass. It announced a new development at the start of February 2015: an ultra-hardened composite material that at this point is known by the name Project Phire.
At an investor meeting, James Clappin, president of Corning Glass Technologies, explained how the firm expects to beat sapphire: "We told you last year that sapphire was great for scratch performance but didn't fare well when dropped. So we created a product that offers the same superior damage resistance and drop performance of Gorilla Glass 4 with scratch resistance that approaches sapphire."
iPhone 7 design rumours: Liquidmetal chassis
Liquidmetal is also said to be under consideration as a material for the chassis, because it's more durable than aluminium: a smaller quantity of this material can be used to achieve the same degree of strength as the metal used for Apple's current iPhones. This would enable Apple to keep the bigger iPhone light and thin, despite the bigger screen.
(But is Apple bothered about device strength any more? Device strength may have been on Apple's mind before the iPhone 6s launch, following the 'Bendgate' controversy that afflicted the iPhone 6 Plus, but 7000-series aluminium and reinforced sides have made the new iPhones almost unbendable.)
Plus, removing the bezels in the bigger iPhone to create an edge-to-edge display would mean Apple could introduce a bigger display without the need to increase the overall size of the iPhone too much.
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