Apple may not be equipping its iPhone 6 with a completely indestructible sapphire screen, but may be using a blend instead.

In a new video, tech blogger Marques Brownlee was able to scratch up a 4.7-inch iPhone 6 dummy screen with a piece of sandpaper. In a video he posted last week, he took a knife to it and the screen was unaffected.

Neil Alford, a professor of materials at Imperial College London (ICL), told the Guardian that a patent Apple has for a sapphire crystal blend explains Brownlee's second vide. Alford previously told the newspaper that the first video could legitimately forecast an indestructible sapphire crystal screen for the iPhone 6.

"Apple has patents for both sapphire lamination - taking two different cuts of sapphire to induce strain and increase its resilience - and for fusing quartz or silica (glass) to sapphire," Alford said in a report published Monday. "So they could certainly do that."

The professor said Apple consulted him on sapphire screens for 18 months. The blend could potentially be used to mass-produce screens for both the 4.7- and 5.5-inch models of the iPhone 6, should Apple release both simultaneously.

In his new video, Brownlee uses two different sandpapers - one that is a six on the Mohr scale and one that is an eight - on the iPhone 5S and on the iPhone 6 dummy.

"The Mohr scale is a relative scale used by geologists and mineralogists to describe minerals and goes from one, which is super soft, to 10, which is super hard," Alford said. "The softest mineral on the scale is talc rising to quartz at number seven and diamond is 10. Corundum, which is sapphire, is number nine.

"I would smash the thing up, stick it under a microscope and you'd have your answer as to whether this is aluminum oxide (sapphire) or silicon dioxide (glass)."