There’s been a lot of debate about whether the iPhone 6 will feature a sapphire glass display. Apple Inc. (NASDAQ:AAPL) made some major investments in sapphire glass last year, fueling speculations about it. Now The Guardian reports that last year, Apple actually talked with experts about making screens from sapphire glass, which is the third-hardest material known to man.

iPhone 6 Apple Sapphire

 iPhone 6 video discussed

Recently a video showing a 4.7-inch display being bent and abused surfaced. The display looked to be sapphire glass, as it was able to resist a knife and being bent by someone’s foot. Professor Neil Alford from the Imperial College, London’s department of materials told The Guardian that the video could be legit. He thinks Apple has made a screen entirely of sapphire glass, which is very hard, resistant to scratches and very stiff.

Apple already has experience using sapphire glass, as it covers the iPhone’s camera lenses and also the Touch ID fingerprint scanner that’s on the iPhone 5S. But if Apple makes the entire screen of the iPhone 6, then it could solve one of the biggest complaints people have about the iPhone: that the screen breaks too easily. Current iPhone models and most other smartphones and tablets use Gorilla Glass, which is manufactured by Corning.

Sapphire iPhone 6 would be pricey

The Guardian notes that using an all-sapphire glass display would come at a high price for Apple. A 4.7-inch display has an area of around 9.5 inches. Because Apple sells tens of millions of iPhones each quarter, it would use up more than 61,000 square meters of the glass per 10 million 4.7-inch iPhones.

With such an ambitious plan in place, it’s no wonder Apple dumped so much money into GT Advanced Technologies Inc (NASDAQ:GTAT)’s sapphire glass making facilities. Just last month, the two companies worked together to open up yet another sapphire plant in Massachusetts. Apple’s multi-year joint venture was formed with the goal of creating industrial amounts of sapphire and then shipping them overseas for assembly. The vague trade documents did not say what the glass would be used for, however.