iPhone 6 sapphire display: is Apple cutting costs with composite materials?

The iPhone 6 screen may not be quite as un-scratchable as previously thought.

Reports suggest the iPhone 6 will feature a sapphire glass display – the same tough material used to protect the fingerprint scanner on the iPhone 5s.

Online reviewer Marques Brownlee put what he claimed is a genuine iPhone 6 display through its paces in a video released a fortnight ago, using a set of keys and a knife on the screen without causing it any damage.

At the time, the display’s resilience was attributed to it being coated with sapphire crystal – the second hardest mineral on earth.

However, a new test using sandpaper suggests otherwise.

Brownlee rubbed the iPhone 6 screen with two types of sandpaper that are softer than sapphire according to the Mohs scale of mineral hardness, and succeeded in scratching it.

While the display fared much better than the iPhone 5s’s Gorilla Glass screen, which is made from toughened glass, it clearly isn’t “pure sapphire”.

The cost factor

Brownlee’s test shows the iPhone 6 screen sits somewhere between 6.8 on the Mohs scale (Gorilla Glass’ toughness) and nine (sapphire’s toughness).

One possible candidate for the material used is fused quartz glass, which is used in watch faces. At seven on the Mohs scale, it’s marginally tougher than Gorilla Glass, but not as hard as sapphire or topaz.

Another possibility is some kind of composite material. However, since impurities are what cause colouration in sapphires, this could result in issues with the transparency of the screen.

Apple uses sapphire in its Touch ID home button in the iPhone 5s. However, it’s up to ten times more expensive to manufacture than Gorilla Glass, which costs about $3 per panel.

This could be one reason Apple may opt for a material that’s very durable, but not quite as expensive as sapphire.