Want CNET to notify you of price drops and the latest stories?

This sapphire smartphone screen is strong, strong, strong

Want a phone screen that really won't break? Make it out of tougher stuff than glass.

Jessica Dolcourt Editorial Director, Content Operations
Jessica Dolcourt's career with CNET began in 2006, and spans reviews, reporting, analysis and commentary for desktop software; mobile software, including the very first Android and iPhone apps and operating systems; and mobile hardware, with an emphasis on iPhone and Samsung. Jessica was one of the first people in the world to test, review and report on foldable phones and 5G wireless speeds. Jessica began leading CNET's How-To section for tips and FAQs in 2019, guiding coverage of practical advice on expansive topics ranging from personal finance to phones and home. She holds an MA with Distinction from the University of Warwick (UK).
Expertise Team leadership, audience engagement, iPhone, Android, iOS, tips and FAQs.
Jessica Dolcourt
3 min read
First Look
Watch this: Virtually indestructible sapphire smartphone screen

BARCELONA, Spain--The smartphone screen on the iPhone above may look like it's made of glass, but it isn't. It's made of sapphire. That's right, the same aluminum oxide compound (AL2O3) better known for brilliant blue gemstones that dangle from ears and throats and can cost a small fortune.

But this particular screen bears little resemblance to Earth-mined rock. Synthetically grown from a "mother" or starter crystal, companies that manufacture synthetic sapphire melt and cut the material (with diamond-tipped saws) into wafers, sheets, you name it.

In the case of the demo, a thin sheet of sapphire has been glued over a regular iPhone 5's chemically hardened Gorilla Glass 2 screen with some transparent adhesive -- it's completely clear. To my eye, the sapphire overlay is indistinguishable from a pane of glass. That is, until I've spent a few minutes deliberately trying to scratch and smash it with a hunk of craggy concrete.

Most of the time, the only result was a building layer of concrete powder that coats the screen, but wipes away clean. One time a tiny nugget of concrete did break from the chunk and stick to the sapphire display. I thought perhaps it was embedded, but it flicked away without any noticeable nicks or indentations. Next to it in the demo, a sheet of Gorilla Glass collected scratches.

Sapphire screens just one step down from diamond-hard (pictures)

See all photos

Depending on the exact formula of chemically reinforced glass, sapphire has approximately 2.5 or 3 times its strength.

Apart from being one of the strongest compound materials there is -- second only to the diamond that cuts it -- synthetic sapphire is highly rigid and won't buckle or melt in high-temperature situations. It is also slow to corrode, conducts heat at low temperatures, and is known for its excellent light transmission for wavelengths well beyond the scope of human vision. The screen was just as responsive as glass when I handled the device.

Grown sapphire is already used in aerospace, military, and medical devices -- especially lasers, protective windows, and highly specialized lenses. It's also used in LED TVs and bulbs, and the high-end watch industry, and it already existed in the iPhone 5 demo unit as a cover material for the main camera lens.

And yes, sapphire has already turned up in a smartphone, making its debut in the Vertu Ti Android phone, which sells for upward of $10,000. Luckily, most future smartphones with sapphire displays won't cost such a jaw-dropping bundle, although the material is more costly, about three or four times the cost of regular glass.

Yet, cost is exactly why we're even able to conceive of sapphire as your phone's topper material. Manufacturing prices continue to drop -- it's all about economies of scale.

GT Advanced Technologies, the company that organized the sapphire display demo, manufactures the giant blocks, or boules, of crystalline sapphire that customers such as China's Zhejiang Shangcheng Science and Technology eventually turn into phone screens and more. It takes 16 days and a furnace at 2,200 degrees Celsius (almost 4,000 Fahrenheit) to create a 250-pound block of synthetic sapphire.

Today there's not enough capacity to create sapphire displays en masse, but we will see an uptick in adoption at the higher end of the spectrum. How much would you pay for a phone with a virtually indestructible screen?

Check out more cool finds, videos, and photos from Mobile World Congress 2013.

Watch this: Bend it like Corning Willow Glass