Apple Watch Sport Ion-X Glass vs Sapphire Crystal Display (Scratch resistance and durability)

September 10, 2014

broken glass

Apple has announced the Apple Watch and the world stood still. Yet, I personally had many questions that I didn’t get an answer for in the announcement event, one of those were regarding the Apple Watch display.

By viewing the Apple Watch produce page on, you can see that the Apple Watch and Apple Watch Edition has a Sapphire Crystal display, but the Apple Watch Sport has a Ion-X Glass display.  We already know that Sapphire Crystal has a Mohs hardness of 9, which is the second most hardened substance on earth, sits below diamond that has hardness of 10 under MOhs scale. Although I did read about the Synthetic Moissanite which is 9.5 on the Moh’s scale.

So Crystal sapphire is super-hard and much more scratch resistant than any other substances than all of the display glass types we have on mobile devices today, but it’s not uncommon to see it on watches. My friend has a TagHeur watch with sapphire crystal and it has this watch for over 15 years — the glass is without a single scratch!  The idea is to use this substance in order to make the Apple Watch and Apple Watch edition scratch proof.

Apple Watch Sport White band

The question is what is Ion-X Glass display and why Apple has chosen to use it in the Apple Watch Sport instead of Sapphire Crystal?

Apple has chosen to go with a different type of glass in order to make the watch lighter and more durable to bumps and drops from my understanding after watching the Apple Watch introduction video and the live streaming event. This is also true to the Watch back which is made using 7000 series silver aluminum, which is lighter and more durable than the 316L stainless steel. It make sense to use a different substance for a sports watch that will be lighter and more durable to impacts. If you are not active, you are unlikely to have your watch damaged by an impact of some sort. So sapphire glass is extremely resistant to scratches and you probably won’t see one in the life of having the Apple Watch, but it can crack upon impact.

This is maybe a reason (except the high price) why Apple didn’t opt for a sapphire crystal glass on its iPhone 6 and iPhone 6 Plus smartphones. So the Apple Watch Sport doesn’t enjoy the same ultra high scratch resistance capability of the sapphire crystal, but it does offer a good degree of protection against scratches and high durability, which is essential for active people.

I personally don’t know yet how strong is the Ion-X Glass compared to the Gorilla Glass 3 or any Gorilla Glass in general. I will update this post when I have an information from a reliable source.

Apple didn’t release any detailed information about the strength of the Ion-X glass compared to the Sapphire crystal, therefore the information presented here is based on reading material I’ve read online. I will update this post when a more detailed information, whether from an official source or not, will be available.

What I know is that the Apple Watch Sport screen isn’t made of single Sapphire Crystal only glass like the other watches. The scree isn’t made of a stronger material because it’s not made of diamond material obviously. This means that a if Apple used a manufacturing process to fortify the glass at the molecular level using ion exchange (aka Ion-X) to create a tougher surface layer. You might think that Apple might only changes the upper surface layer and the other part of the glass is still Sapphire crystal, but as far as understand, if Apple calls it Ion-X glass and not emphasizing the Sapphire Crystal, it’s not a Sapphire crystal. So it should be a glass that is not hard as Sapphire Crystal but it is still highly resistant to scratches and protected against impact in a higher degree of Sapphire Crystal (only in terms of impact protection), if not, Apple wouldn’t use it in the Apple Watch Sport model — seems logical isn’t it, but that’s not an answer.


According to Apple Watch Sport page on website, the Ion-X glass helps makes the Watch Sport lighter (inc. the 7000 series aluminum). Furthermore, it’s written that the glass is made using alumina-silicate glass. This glass is especially resistant to scratches and impact. So according to Apple it’s much more durable than regular glass, but what I understand from this that it’s not on par with Sapphire crystal as far as scratch-resistance is concerned.

We know that Sapphire crystal has a MOH hardness of 9, so what I wanted to know is what is the MOH hardness of alumina-silicate?

– I’m still searching, and I think that could give us a more accurate understanding of that glass strength compared to Sapphire Crystal. If you find anything, please leave a comment below and share your findings :)

Update 2:

According to an article I’ve read on, Corning says it’s word about using Sapphire on high-end watches, stating that Sapphire breaks more easily, whether their Gorilla Glass shown better results under the same test conditions. You need to apply three times the force (that breaks the sapphire) in order to break the Gorilla Glass, so it’s 3 times stronger (applying force to bend it), therefore the sapphire is more prone to shatter. Sapphire is harder to scratch and 67 percent heavier. This finding stands parallel with what I assume was the choice of Apple going with Ion-X instead of sapphire on the Apple Watch Sport model. It’s a very interesting article,  I recommend reading it. Also check the video below..

Sapphire vs Gorilla Glass:

Again, this is Gorilla Glass vs Sapphire. I think that the Ion-X is Apple’s somewhat equivalent to the Gorilla Glass 3. The Gorilla Glass is also toughened by ion exchange , same process as the Ion-x. Apple mentioned this process in the Apple Watch product page. I can assume two things: that either Apple re-branded the Gorilla Glass and calls it Ion-X (unlikely), or it’s made elsewhere and if so, is it stronger than Gorilla Glass 3?

After reading a bit more, I’ve read about the $578 million contract that Apple made with GT Advanced Technologies for providing it with sapphire for the  fingerprint home button (touch sensor) and we can obviously assume that for the Apple Watch and Apple Watch Edition watches as well.  This company might also be producing the Ion-X Glass  (a chemically strengthened glass) for Apple as well. An article on (in French) raised this question, asking whether the new Apple branded strengthened glass is made by GT Advanced Technologies Inc. or by Corning — no answer though.

I personally was confused with all those “strength”, “toughness”, “hardness” terms. In the article it was mentioned that the sapphire is harder than the chemically strengthened glass. “Harder” or “Hardness” refers to how resistance is the material to scratches, and “Toughness” refers to how much it takes to break as a whole once it suffer from small fragmentation. Most articles that I’ve read mentioned that Sapphire shatters more easily when force pressure is applied.

As for now, my take is that Apple has chosen Ion-X glass instead of sapphire for its Apple Watch Sport for its extra durability and  weight less, and that Sapphire has better scratch resistant protection and it’s stronger overall, but it more prone to break upon drop or impact.

I have a watch with single sapphire crystal cover. It’s with me a few years and it was gone thought lost of bumping and dropping without any scratch or any breakage. Add to this the chance that your watch will actually get such an impact that can break the glass, even while doing sports. I think that most people will prefer a watch that is less likely to get scratched — who wanted to wear a scratched Apple Watch? (Is it an option to replace the display, and if so how much it cost.. more questions).

I will update this post when I have more information.

BTW, Check out the Apple iPhone 6 and iPhone 6 Plus size comparison here.

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  • Patrick Thornton

    I would not be surprised if Ion-X is either Gorilla Glass or a modified version of it. All iPhones have used Gorilla Glass, and the iPhone is the first phone to sport it.

    I am curious to see how much the Ion-X glass is about saving weight versus better impact resistance. I’m leaning toward the Apple Watch because I have been able to scratch Gorilla Glass on just about every device I own, but I do plan on using the Apple Watch to work out with, so a more impact-resitant screen may be better.

    • cameradebate

      I also decided that the Apple Watch might be the best option for me. Having a sapphire glass is crucial to prevent scratches, which can certainly (the scratches) ruin your experience with the watch, as scratches are more prominent on this small screen.. and it doesn’t make it look good either, considering it’s such a slick looking device.

      • john m.

        If you care about scratches then you’d need to pick the **Sport** edition since it’s made for more active people. No??? The entire article implies that ion-exchange glass is STRONGER than the standard model.