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Sapphire vs Corning’s Gorilla Glass: what is sapphire and is it really tougher?

Posted: , by Victor H.

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Sapphire vs Corning’s Gorilla Glass: what is sapphire and is it really tougher?

If you’ve been following the news lately, you might be under the impression that Gorilla Glass, the tough tempered glass that protects your phone from scratching, is on its way out. Sapphire is the new buzzword - Apple is said to plan to adopt it in its new iPhone 6, and reports claim the company has purchased enough furnaces to blast out 200 million sapphire panels for its upcoming smartphone.

Moreover, videos have popped up showing how sapphire glass is nearly unbreakable, even when you torture it to the extreme: cut it, bend it, drop it, and it still remains intact. We don't even need to rely on the videos alone: there already are real devices with a sapphire display like the Kyocera Brigadier (watch us torture its sapphire cover glass here) that have proved extremely tough in testing. At the same time, we know little about the actual material itself and how exactly it compares against Corning’s Gorilla Glass.

What’s sapphire and how it’s manufactured

Sapphire is a gemstone that naturally occurs in nature in various forms and colors. A red sapphire is actually called a ruby, and blue sapphire is often used in jewelry, but sapphire also occurs in a perfectly color-less, transparent form, and that’s the exact type that could come in use in smartphones.

What makes it so special, though? Sapphire is one of the hardest materials on Earth, ranking 9 out of 10 on Mohr's scale of hardness, falling short of just diamond that has 10 out of 10. In practice, this means that only materials like diamond can scratch sapphire, and unless you're carrying diamonds in your pockets (we sincerely wish you to), a sapphire display would remain perfectly pure and scratch-free after months of use. Glass in general ranks 5 out of 10 on the same scale, and is much less protected from common pocket threats like keys and sand.

Sapphire production process

Sapphire production process

With a business measuring more than 30 million smartphones sold every quarter, Apple needed to not only secure sapphire orders, it needed a lot of them. Rather than mining it from ores, though, and getting it in its pure form, it’s much more practical to ‘grow’ synthetic sapphire in furnaces. The actual process of manufacturing such sapphire boules is very interesting, and involves furnaces getting heated up to temperatures as high as 3300 degrees Fahrenheit (1815 C), to melt a hockey pluck-sized piece of the gemstone mixed with aluminum oxide powder.

In comparison, Corning's Gorilla Glass is essentially a type of tempered glass and, while details of the particular Corning method of toughening it up remain a secret, we know that Gorilla Glass emerges after a sheet of glass is dipped into a bath of salts, a material that shrink-wraps around the actual glass substrate, adding pressure around the glass material. This is what what adds that extra bit of strength to Gorilla Glass.

The problem with this layer, though, is that when you scratch that 15-micron thin film you damage the material and release the stress. After accumulating a few of those scratches, it’s very likely that at some point when the phone drops you’ll get a crack along that scratched line (we've all seen the spider webs of cracked phone screens).


Sapphire vs Corning’s Gorilla Glass: what is sapphire and is it really tougher?
Let’s get one thing out of the way: even though sapphire is tougher to scratch, it’s still a brittle material, meaning that dropping your future sapphire-protected phone from afar on the concrete floor could still break its screen.

It gets interesting when we dive deeper in the numbers, though. We've already told you about the general rating of sapphire (including synthetic sapphire) on Mohs scale (9 out of 10) and how it compares to glass (5 out of 10). The chart below gives even more technical details, and while it is produced by sapphire maker GT Advanced, the numbers are not skewed in favor of any of the materials.

You can see a clear dominance of sapphire in practically every aspect: the number you would probably be most interested in is 'fracture toughness' that measures 2.3MPa√m, nearly triple the fracture toughness of Corning's Gorilla Glass, but others as well: sapphire is tougher by means of elasticity and hardness.

Sapphire is also brittle like glass, but much harder to scratch

Interestingly, sapphire is also nearly 70% heavier, denser than glass (3.98 grams/cm3 vs 2.54 g/cm3), so that means that to have the same weight, a sapphire cover glass would also have to be thinner. Is this possible? We're yet to see, but if not, sapphire would come with one downside of increasing the overall weight of a device.

Sapphire properties, as per GT Advanced

Sapphire properties, as per GT Advanced

Cost of sapphire vs cost of glass, and future use

One big obstacle that companies like Apple have to overcome with sapphire is its multiple times higher price than glass. Sure, we’ve been talking about all the flaws of Corning’s Gorilla Glass, but it ends up costing around $3 apiece. Sapphire, in comparison, used to cost around $25 apiece, and only recent developments have allowed dropping its price to below $10 levels, according to estimations by industry sources.

Apple has invested some $700 million in a factory in Mesa, Arizona that can produce double what the current global capacity of furnaces around the world is. With such scale, the price of sapphire touchscreen glass could have dropped even further down, and finally allowed for this tough material to start protecting one of the most commonly used daily gadgets - our smartphones.

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posted on 19 Aug 2014, 07:57 7

1. akki20892 (Posts: 3902; Member since: 04 Feb 2013)

Its expensive.... And no need.
My nexus or previous N8 didn't got any scratches on screen.... GG is best...

posted on 19 Aug 2014, 08:16 4

4. neela_akaash (Posts: 1229; Member since: 05 Aug 2014)

GG is more fragile than the DRAGONTRAIL from AGC(used in xperia Z2). But both prevent scratches very well.

posted on 19 Aug 2014, 12:56 7

22. Finalflash (Posts: 3527; Member since: 23 Jul 2013)

Scratches were never really a problem though. The issue is screens shattering and this sapphire situation will only make that worse seeing as how it is more brittle and less flexible than GG. Honestly this will be the best money making strategy for Apple from this point forwards. They're the only ones that can replace it seeing as how they are the only ones that produce sapphire in that quantity. If they fix screens for $100-150 a piece, that is literally 3/4 the cost of making a full iPhone. That is probably $75-100 in profits, the amount they make on a full iPad.

posted on 19 Aug 2014, 14:36 2

23. BlankSpaceNai (Posts: 127; Member since: 23 Apr 2014)

+1 to this

I think you just basically told the 'actual' reason for the push of sapphire glass. No money in the cure, only the medication

posted on 19 Aug 2014, 08:19 8

5. eisenbricher (Posts: 973; Member since: 09 Aug 2012)

Right said, and most people end up using screen protectors so it makes sense to pay much less for Gorilla Glass than the Sapphire display.

As a side note I strongly recommend use of Sapphire glass to protect camera window. While small scratches do not make noticeable difference on smartphone screen, they really do affect quality of Camera pics as device gets older and older. There isn't much awareness about protection of camera lens in smartphones.

The camera window degradation is especially evident when you click pictures of bright lights (you see numerous weird lens flares).

posted on 19 Aug 2014, 09:10 1

16. superduper (Posts: 151; Member since: 20 Oct 2013)

Bad idea for a camera as it leads to lens flare. iPhone 5 has sapphire camera lens, but early reviewers noted purple lens flare problem.

posted on 19 Aug 2014, 11:16

21. Iodine (Posts: 1395; Member since: 19 Jun 2014)

Thats hardly a problem of sapphire camera cover, as sapphire is one of the most transparent materials.

posted on 19 Aug 2014, 08:19 1

6. sar44 (Posts: 278; Member since: 14 Apr 2014)

perhaps gg4

posted on 19 Aug 2014, 09:37

17. ecologer (Posts: 31; Member since: 25 Jul 2014)

Do you know when this Corning anti-reflective coating will be available?
Looks very promising.

posted on 06 Feb 2016, 09:36

32. ecologer (Posts: 31; Member since: 25 Jul 2014)

I'm still eagerly waiting for the new anti-reflective coating to appear. Seems there's no news yet?

posted on 19 Aug 2014, 08:00 1

2. chunky1x (Posts: 270; Member since: 28 Mar 2010)

I'm in if the cost of the whole phone is the same or cheaper.

posted on 19 Aug 2014, 08:13

3. chunky1x (Posts: 270; Member since: 28 Mar 2010)

"In practice, this means that only materials like diamond can scratch sapphire, and unless you're carrying diamonds in your pockets (we sincerely wish you to)"

Challenge accepted. I have a diamond grit sandpaper in my desk. Also, most women have a diamond grit nail file lying around their purse.

posted on 19 Aug 2014, 11:05 1

20. Augustine (Posts: 1043; Member since: 28 Sep 2013)

Actually, sapphire can also be scratched by sapphire.

posted on 19 Aug 2014, 15:18

25. jaytai0106 (Posts: 1888; Member since: 30 Mar 2011)

I'm pretty sure diamond is tougher than sapphire. But let's find out :)

posted on 19 Aug 2014, 08:29 1

7. Scott93274 (Posts: 5396; Member since: 06 Aug 2013)

What I want to know is how many people who currently have an iPhone have a screen that's all scratched up? I have my Moto X that's in mint condition as well as my 2+ year old Galaxy Nexus with 0 scratches. Will sapphire glass turn out to be nothing more than a bragging rights feature and in reality not make a lick of difference to the end user?

posted on 19 Aug 2014, 08:30

8. microsoftnokiawin (Posts: 1236; Member since: 30 Mar 2012)

knowing apple they'll find away to make it scratchable anyway jokes aside

apple is off again creating a new trend in the smartphone market !

posted on 19 Aug 2014, 08:44 3

10. cybertec69 (Posts: 29; Member since: 17 Aug 2014)

New Flash, Kyocera already has a phone on the market with Sapphire glass, and it's on Verizon, the Brigadier.

posted on 19 Aug 2014, 09:01

12. microsoftnokiawin (Posts: 1236; Member since: 30 Mar 2012)

yes i know that but there's a different between setting trends and being first
if you look at the iphone 5s something i would personally never touch but i still cannot deny that they started a fingerprint scanner trend with the s5 following and close and other manufacturers rumours !

posted on 19 Aug 2014, 08:39

9. ManusImperceptus (Posts: 724; Member since: 10 Jun 2014)

"a sapphire display would remain perfectly pure and scratch-free after months of use."

Months? Why not years? Why not forever? If it's as tough as described, and provided it's not actually been dropped and cracked, why would it only stay scratch-free for mere months? I'd expect more after reading about near-diamond hardness...

posted on 19 Aug 2014, 08:46 3

11. cybertec69 (Posts: 29; Member since: 17 Aug 2014)

I own a few watches with Sapphire glass, they are many years old and are still scratch free, Sapphire is really hard to scratch.

posted on 19 Aug 2014, 09:01 3

13. Taters (banned) (Posts: 6474; Member since: 28 Jan 2013)

Looks like it loses badly in the most important area. Refractive index. Which means Apple needs to add an extra layer of non sapphire to correct the viewing angles and purple fringing of its sapphire camera lenses. Which defeats the purpose of being more drop proof.

Personally I wouldn't give up better value, viewing angles, and less colour shifting for a more scratch proof material. But I don't control the market. Apple and Samsung does.

posted on 19 Aug 2014, 09:06

15. Scott93274 (Posts: 5396; Member since: 06 Aug 2013)

Whatever happened to the glass that has almost no reflective properties whatsoever, phone arena did an article on it a while back. That would be something worth getting excited about.

posted on 19 Aug 2014, 09:01 2

14. itsdeepak4u2000 (Posts: 3718; Member since: 03 Nov 2012)

No thanks, you are costly. GG is best, GG FTW.

posted on 19 Aug 2014, 10:04

18. tyger11 (Posts: 194; Member since: 29 Oct 2012)

If the rumors are true, and the next generation of Gorilla Glass has the anti-reflective treatment that eliminates 99%+ of reflections, then Sapphire Glass will lose. I've been waiting for this tech to make it into products since the development announcements a few years ago (2 or 3 different teams have developed this tech).

posted on 19 Aug 2014, 10:55

19. newuser1 (Posts: 276; Member since: 10 Dec 2010)

It prevent scratch but if you drop the phone. I will still break.

posted on 19 Aug 2014, 14:37

24. avalon2105 (Posts: 311; Member since: 12 Jul 2014)

Still would choose Gorilla Glass over it. My G2 with second generation GG is still spotless, no scratches whatsoever and even more importantly (for my OCD) easy to clean. What I would like to see in next gen GG is shatter-proofing like in Dragontrail glass. Sony is using it and I can say that it works. Had my Xperia S drop on hard ceramic tiles a lot of times and the screen never got damaged, let alone shattered. And also better oleophobic coating for people who want to keep their screen always clean.

posted on 19 Aug 2014, 17:49

26. gigaraga (Posts: 1454; Member since: 29 Mar 2013)

Sapphire Glass should be the next innovation. Although smartphone prices would skyrocket. That means iPhone 6 going to double...the price?!?!

posted on 19 Aug 2014, 20:57

27. Af1rPA (Posts: 711; Member since: 12 Jun 2014)

That graph of the "Knoop Hardness" doesn't shows Apples synthetic Saphire glass which will probably only have a hardness of about 7? Still better than GG.

posted on 19 Aug 2014, 21:54

28. a_tumiwa (Posts: 378; Member since: 16 Mar 2012)

it's good if it is better, just dont increase the price of phone to customer

posted on 20 Aug 2014, 01:46

29. parthoman (Posts: 80; Member since: 18 Aug 2014)

now are the supporters of apple gonna get a longer and bigger iphone made of sapphire glass ?

are they creating a phone or a weapon?

like come here android fella " imma cut ya phone with my sapphire phone , aka iphone, aka beats phone , aka...."

corning gorilla glass or other glasses are okay , if apple could do anything is change the form factor of its phone or make something innovative or what they call revolutionary.

and after burning the hell out of those furnances they will show the neatly designed green leaf ad in their site and solar panels " yes we are nature friendly ..."

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