The leaked component that’s being touted as the front screen of the upcoming iPhone 6 got a good workout in a video test by Youtube regular MKBHD (Marques Brownlee) when it first broke cover, and now Brownlee is back with a new video that takes the durability tests even further. This second round involves exposing the supposedly super-strong sapphire-based material to a true test of strength – scratching by sandpaper, a material with a much higher Mohs scale hardness rating than any steel knife or set of keys.

In the video, you can see that Brownlee uses both garnet and emery-based sandpaper, both of which have Mohs scores that exceed the hardness of existing Gorilla Glass. These fall under the hardness rating of pure sapphire, however, which is second only to diamond when it comes to hardness for naturally occurring substances. The iPhone 5s, as you can see in the video, doesn’t stand up well to scratches administered by the sandpaper – but the iPhone 5s home button, which is pretty much pure sapphire, does.

The so-called iPhone 6 display also isn’t immune to the effects of the sandpaper – but it does stand up much better to the abrasion than the display of its predecessor. And as Brownlee explains, it doesn’t matter so much that the screen suffered a few scratches under these extremely artificial testing conditions: Its overall durability and flexibility mean it should be safe from almost every real world threat it might encounter in your pockets or your bags.