One of the most important new features of the iPhone 6 is all but confirmed, yet has not grabbed many headlines ahead of the handset's official unveiling.

According to the Guardian, one expert in particular strongly believes Apple will use the ultra-tough Sapphire crystal glass for the iPhone 6's display. The handset is expected to launch this fall and several leaked images and videos have claimed to know its various specifications.

In a new video of from Marques Brownlee, the tech blogger stepped on, bent and took a knife to what appears to be the iPhone 6's sapphire crystal display. Neil Alford, a professor in Imperial College London's (ICL) department of materials, said he believes the new video is legit.

"I think Apple have been quite cunning," Alford told the Guardian. "What I think they've done is make a screen out of sapphire, which is incredibly scratch resistant, incredibly hard and has a high elastic modulus - meaning it's very stiff."

Apple did buy a sapphire crystal factory in Arizona, but producing display screens for tens of millions of handsets could be tedious and costly. The upside is obvious, as Apple would have a highly advanced handset whose screen was not just scratch-resistant, but tough to the point of indestructability.

Apple already used sapphire crystal for past iPhone model's camera lenses and the Touch ID fingerprint sensor of the 5S.

"I remember the Apple folk coming to speak to me about 18 months ago to discuss sapphire screens," remarked Alford. "They've obviously been busy since then, working with a sapphire manufacturer.

"It's not a surprising thing to do, but it's quite a large area they're producing and that's really quite a challenge. I'm pretty impressed with that, actually."

According to a U.S. patent obtained by AppleInsider.com, Apple is considering building future iPhones made completely out of glass. Though the iPhone 4/4S's glass front and back panels are prone to cracking, sapphire crystal apparently has Apple feeling confident in weighing an all-glass handset.

Patents do not provide any indication for when the filer plans to put anything to use, so there is always a chance Apple never makes an all-glass iPhone. For all the leaks, rumors and expert input, Apple is apparently ready to use sapphire crystal soon.