Last week, a video posted by YouTube user Marques Brownlee showed the alleged front panel of the 4.7-inch iPhone 6 being put through a number of scratch tests and significant bending. Now, Brownlee has released another video putting the same display through more rigorous scratch tests, this time with two different types of sandpaper.

Brownlee cites the Mohs scale of mineral hardness in his testing, which is a scale rating mineral hardness from 1-10. The iPhone 5s' Gorilla Glass display is rated at a 6.8, while sapphire crystal, which Apple uses for the iPhone 5s Touch ID home button, is rated at 9. The two sandpapers used for the test include garnet, which is rated at a 7 on the Mohs scale, and emery, rated slightly above an 8.

Upon testing, both types of sandpapers were able to scratch the iPhone 6's front panel, but it did show better resistance than the Gorilla Glass display for the iPhone 5s. Notably, the sapphire Touch ID home button on the iPhone 5s did not display any marks after being scratched by the sandpaper. This would indicate that the alleged front panel from the 4.7-inch iPhone 6 is not sapphire crystal, but instead perhaps a next-generation version of Gorilla Glass. It is also possible that the panel could be a hybrid sapphire coated display, which was patented by Apple last year.

A report last month claimed that Apple would only be using a sapphire display in the larger 5.5-inch iPhone 6 over concerns about high cost and limited supply. Earlier rumors had indicated that Apple would have enough sapphire glass for production of both iPhone 6 models and the iWatch in 2014.

Apple is expected to announce the iPhone 6 in early September with a release coming a few weeks later. It is unclear whether the 4.7-inch and 5.5-inch versions of the device will launch at the same time, with recent reports claiming that the larger iPhone 6 will be released later this year or in early 2015. In addition to a larger display, both models of the iPhone are expected to include a faster A8 processor, a thinner profile, an improved camera, and Apple's new iOS 8 mobile operating system.