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iPhone 6 indestructible Sapphire glass: let's set the record straight

“Indestructible”, as an industry term, is never literal. Just like “unparalleled”, “outstanding” and “best in class”. When we first heard of Sapphire glass, in conjunction with the iPhone 6 screen, the word “indestructible” was thrown around a lot, but even then, we knew to be careful with the hype.

YouTuber Marques Brownlees wasn’t too convinced either, and decided to put the iPhone 6 Sapphire screen to the test.

The goal was not to prove the indestructibility of the iPhone 6 screen, but rather to understand how mineral strength actually works, using what is known as the Mohs Hardness Scale.

The Mohs scale gives a rating to each material, and by that scale, a mineral with a lower rating cannot scratch one with a higher rating and vice versa.

For example, quartz has a 7.0 rating, which means it cannot be scratched or damaged by a steel nail, rated 6.5, but it can be drilled through by a masonry bit, which is rated 8.5.

Pure Sapphire is rated 9, which is pretty close to being indestructible. The test performed by Marques involves two types of sandpaper: Garnet, rated 7.0, and Emery, rated 8.0.

Both Emery and Garnet successfully, and extensively scratched the iPhone 5s Gorilla Glass, which was to be expected.

When putting to the test the iPhone 6 Sapphire glass, Marques reports disappointing results, as both kinds of sandpaper managed to scratch the screen, yet not as extensively as they did on the Gorilla Glass.

So how is it possible that Sapphire Glass, which is supposed to be rated 9 on the Mohs scale is softer than both Emery and Garnet, rated respectively at 7 and 8?

The truth is, the iPhone 6 screen is not pure Sapphire, and for two very good reasons:

  1. Sapphire is not a flexible material. Flexibility is a requirement on mobile devices. Regardless of what Mohs’ Hardness Scale dictates, smartphones dropping from a distance on any hard surface, will shatter due to natural laws of physics, and flexibility allows a device to reduce that chance by introducing shock-absorbing materials.
  2. Sapphire Glass is expensive, and if GT Advanced Technologies hydrogen particle accelerator weren’t involved in the production of the glass, production costs would put extreme pressure on Apple’s ability to make the iPhone 6 “indestructible”.

By the same token, as Marques mentioned in the video, Apple has already filed a patent which suggests that the company might be working on a way to modify Sapphire’s mechanic properties in such a way as to be able to make it flexible.

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