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What Is Sapphire Glass and Why Does It Matter for the iPhone 6?


You may soon be able to stab your iPhone with no consequence. Screen shot via Marques Brownie.

If you’ve paid any attention to Apple’s hyperactive rumor mill, you’ve probably heard the term “sapphire glass” thrown around a bit. Yes, it sounds like the name of some drug Lil’ Wayne would be into. But it’s also an intensely durable material that could revolutionize the way we handle our Apple gadgets. Below, a quick explainer on what this mysterious resource is and why everyone (including the creator of Gorilla Glass) is in a tizzy over it.

What does Apple use now?

Currently, the front cover on the iPhone 5S is made of Gorilla Glass, a thin, durable material made of alkali-aluminosilicate by U.S. glassmaker Corning Inc. However, two of its most precious parts are already encased in sapphire glass: its 8-megapixel camera and the Home button’s Touch ID fingerprint sensor. The camera gets this special treatment for obvious reasons: all your photos would be affected if its cover got scratched or smashed. And when it comes to the sensor, it’s also important that its enclosed in a scratch-free, crystal clear surface.

OK, but what is it?

You’re probably familiar with sapphire gems, the dreamy blue September birthstones that are worn as jewelry and encrusted in statues.

According to Neil Alfred—a professor of physical electronics and thin film materials at the Imperial College in London who spoke with Apple about the properties of sapphire glass earlier in the year—the gemstone is actually almost the same exact composition as its glass counterpart.

"There are some minor impurities in sapphire that make it go blue,” Alford told Yahoo Tech. “Sapphire crystal, which is artificially made, is actually purer than a piece of sapphire that you would get in your ring.”

Sapphire glass, however, is a synthetic form of that compound, and is named for its transparency, not its consistency. It’s incredibly clear, even for wavelengths of light that are way out of the threshold of what normal humans can see. It’s also pretty impossible to scratch, as evidenced by this video published by Marques Brownlee in the beginning of July.

Whether or not the above screen is truly that of an iPhone 6 remains to be seen. But the fact that something so thin and so clear can be stabbed by a sharp knife without so much as a scratch implies that we could soon reach a new era of mobile durability.

Why should I care?

You, dear reader, have likely done something abhorrent to your smartphone. Perhaps you dropped it from a plane, allowed it to be crushed by a 50-pound speaker, or simply let it fall out of your pocket onto the cold, hard concrete. A lucky few survive these events unscathed, but many more perish. Sapphire glass means a more durable, resilient iPhone that is less likely to be beaten up by the daily chaos that is your life. It’s harder to break or scratch, can withstand high temperatures, and won’t chemically corrode.

Is it better than Gorilla Glass?

It may be in some ways. While the two are both very transparent and strong, sapphire has a higher dialectric constant than Gorilla Glass. That means it can hold a charge for longer periods of time. Alford surmises that this may have effect on the iPhone’s display, “because they use some sort of a capacitve mechanism to activate the touch screen.” That being said, he’s skeptical.

"I’m not sure whether it’s that much of an advantage other than it’s a fantastic sales ploy by Apple," he told Yahoo Tech. "I wish some of my scientific papers got as many hits as the interviews I’ve done on this."

Well, if it’s SO great, why haven’t they used it as the front screen all along?

Sapphire glass is truly dope, yes. And because of that, it’s long been used to make camera lenses, cover expensive watch faces, and even as a display screen in Vertu’s high-end 4.3-inch Constellation phone.

But like most truly dope things, it costs a lot of money to make, especially in large amounts and in the shape of such an expansive surface area.

Sapphire crystals are made from aluminum-oxide powder. Once heated and cooled, you can cut them into glass-like layers. But unlike aluminum, a material used to make many an iPhone product, sapphire is incredibly hard to cut, mold, or polish.

In fact, to do so requires diamond slicers. Yes, you heard that right: Apple is likely carving the casing for your next iPhone (or iWatch) with diamond-encrusted tools at the processing plant it opened with GT Technologies Inc. in Mesa, Arizona. 

That being said, the iPhone 6 is rumored to come in two sizes: a 4.7 inch screen, and a 5.5 inch screen—meaning the company is probably scrambling through very tedious processing steps so it’ll have enough inventory come pre-order day. The Wall Street Journal even reported that Apple is considering only offering the screens with the higher priced model.

"The big issue," as Alford sees it, "is whether Apple can control the costs."

I see.

We clear now?


I see what you did there.

Follow Alyssa Bereznak on Twitter or email her here.