The iPhone 6 will be the most radical redesign in the iPhone’s history, from larger screen to a new display it will mark another milestone in its flagship smartphone.

Sapphire crystal screens: why Apple is interested in a gemstone

Apple has invested in the production of a new type of smartphone screen that is harder and more resistant to scratches. Its new sapphire crystal production plant is expected to be up and running, but what has a precious gemstone got to do with smartphone and tablet computer screens?

Sapphire is a super-hard form of optically transparent crystal that looks and behaves like glass or diamond. Sapphire takes many forms, one of which is a gemstone. It comes in various colours including yellow, purple, orange, green and red. A red sapphire is known as a ruby, but the most recognized sapphire gemstone is of blue tint.

Photograph: Bossi/flickr
Photograph: Bossi/flickr

It’s the impurities in sapphire gemstones that give crystals their colours. The sapphire crystal used for screens, however, is colourless because it is more pure, lacking any of the iron, titanium, chromium, copper or magnesium that makes mined gemstones unique.

Sapphire gemstones are commonly mined like most other precious gems, but the sapphire crystal used in most non-jewelry applications is artificially manufactured.

The first synthetic sapphire was created in 1902 by a French chemist called Auguste Verneuil. Since 1902 various methods of making sapphire have been developed, but generally they use high heat and pressure to turn aluminium oxide power into crystal.

iPhone 6 screen could be sapphire-glass blend

A new video that apparently shows a 4.7in sapphire screen from an iPhone 6 being scratched by sandpaper could “certainly” be a legitimate blend of sapphire and glass.

Sandpaper scratch test performed on iPhone 5S and alleged iPhone 6 screens. Photograph: Marques BrownleeSandpaper scratch test performed on iPhone 5S and alleged iPhone 6 screens. Photograph: Marques Brownlee

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.

Apple currently uses sapphire crystal for its camera lenses and the cover of the iPhone 5S’s Touch ID fingerprint sensor, but the super-hard material could make excellent screens that are much more scratch resistant than traditional glass and potentially even Corning’s Gorilla Glass, which covers the majority of smartphone and tablet screens.

The hardness of the material

The new video shows Marques Brownlee scratch both an iPhone 5S screen – which uses the third generation of Gorilla Glass – and the alleged iPhone 6 4.7in screen with two different types of sandpaper.

A softer garnet sandpaper, which is about six on the Mohr scale, and emery, which is about eight on the Mohr scale, were used on the two screens.

“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,” explained Alford. “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.”

“The relative hardness of sapphire is 400, compared to quartz which is 100, so it is a lot harder than quartz,” Alford stressed.

The hardness of a material is rated in Mohs, where talc is rated as 1 Mohs and diamond 10 Mohs. Glass ranks around 5.5 to 7 Mohs, but sapphire crystal has a hardness of 9 Mohs, making it only slightly less hard than diamond.

Mohs Hardness scale Source
Mohs Hardness scale:Source

The Mohs rating of Corning’s Gorilla Glass, which is the chemically hardened glass used to make many smartphone screens including those found on the Google Nexus 5 and Samsung Galaxy S4, has not been released, but it is expected to be around 7 Mohs.

Regular steel has a hardness of around 4 Mohs, but hardened steel a hardness of around 8 Mohs. Anything made of a substance that is harder with a higher Mohs rating will scratch anything that is not as hard, meaning a sapphire screen could resist scratches from almost anything likely to be carried in a pocket.

Is it Indestructible?

In the video, Brownlee manages to scratch both iPhone screens with the sandpaper, with the alleged iPhone 6 screen showing higher resistance to scratching with the garnet and emery sandpapers than the iPhone 5S Gorilla Glass screen. The sapphire home button of the iPhone 5S resisted all scratches from both sandpapers.

Brownlee concludes that the leaked iPhone 6 screen could be a blend of sapphire crystal and traditional glass.

So What Are Apple Actually using?

A synthetic sapphire or sapphire crystal.

Sapphire crystals are made from aluminium oxide powder, compared to silicon dioxide in standard glass. Once heated and cooled, it can be cut and formed into glass-like layers – known as sapphire glass. The optically transparent material has long been used for camera lenses as well as the screens of high-end watches because of its combination of scratch resistance and high transparency.

Sapphire has many advantages over glass, but has been prohibitively expensive to produce in large areas despite abundant raw materials. Creating artificial sapphire is not a problem in smaller areas for electronics and other uses, much in the same way artificial diamonds are used in manufacturing.


You can watch Brownlee’s full Video

Source The Guardian