Amid rumors of Apple's use of sapphire for its next-gen iPhone's display, Corning – the company behind Gorilla Glass, the material used in current-generation iPhones and iPads – has come out with a “blistering critique of sapphire crystal,” according to a recent report.

The news comes from CNET, which explains that Corning senior vice president Tony Tripeny made the comments at the Morgan Stanley Technology, Media, and Telecom Conference on Tuesday.

His remarks came in response to a question posed by Morgan Stanley's James Fawcett, who said: “So we mentioned Sapphire and obviously there is one large handset and device maker that people suspect maybe looking at Sapphire. And at least from a Corning perspective, (what are) the puts and takes of Sapphire versus glass?”

Tripeny answered:

When we look at it, we see a lot of disadvantages of Sapphire versus Gorilla Glass. It's about 10 times more expensive. It's about 1.6 times heavier. It's environmentally unfriendly. It takes about 100 times more energy to generate a Sapphire crystal than it does glass. It transmits less light which (…) means either dimmer devices or shorter battery life. It continues to break. I think while it's a scratch resistant product it still breaks and our testing says that Gorilla Glass (can take) about 2.5 times more pressure that it can take (…) Sapphire on. So when we look at it, we think from an overall industry and trend that is not attractive in consumer electronics.

Corning's perspective on sapphire glass is no secret: the company even has a public Web page, “Corning Glass vs. Sapphire,” where a video outlines such differences (with an equally heavy bias towards Corning's product, of course).

Tripeny added that the formation of sapphire takes around 4,000 times longer than Gorilla Glass and requires a “significantly higher melting temperature” – both serve to increase the price of sapphire displays.

He went on to explain that the hardness of sapphire can also make machining a problem, too: “Then the cost per unit increases exponentially because when you have defects in boundaries in the crystal growth process, you essentially cut them out. And so unlike glass, where we have developed technologies so that we can have (a) very large pristine pieces of glass, when you have that on crystals, what you end up doing is always having a yield issue.”

The promise of sapphire comes in its ultra-durability, however, and Apple has already utilized the material's impressive properties for both its camera modules and the iPhone 5s handset's Touch ID.

After signing a deal with the Arizona-based GT Advanced Technologies, Apple is also in the process of manufacturing its own sapphire glass for yet-to-be-announced products. It's thought that a sapphire glass display could be used for a 5.5-inch iPhone 6 handset, at the very least. Though if one recent report has it right, Apple has also purchased a three-year supply of 4.5-inch sapphire glass displays.

Corning's Gorilla Glass, on the other hand, is used in the new Pebble Steel, the second-generation smart watch which launched earlier this year. However, much like its next-generation iPhone, Apple's own anticipated smart watch is expected to feature a sapphire display, too.

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