Bad news for those waiting for a large-screen iPhone: The rumored upcoming 5.5-inch iPhone 6 might not release this year.

The iPhone 6 is expected to come in two sizes, a 4.7-inch model and a 5.5-inch variant. Excitement centers around the 5.5-incher, as it will finally give Apple fans an option only Android users have had up until now.

"Production bottlenecks on 4.7-inch iPhone 6 center on the yield rate of in-cell touch panel and metal casing," KGI Securities analyst Ming-Chi Kuo wrote in a report.

"As in-cell touch panel becomes larger in size, the edge of the panel may become insensitive to touch. Meanwhile, under new manufacturing process for the iPhone 6 metal casing, color unevenness is an issue."

Apple has not announced or said anything regarding the iPhone 6. So be sure to take this with a grain of salt. Previous reports indicated that Apple would simultaneously release both iPhone 6 sizes in the fall, revealing them in September, as usual.

Another iPhone 6 rumor is the inclusion of sapphire glass. It's been rumored for some time that Apple plans on changing the display to sapphire crystal glass. Sounds fancy, you say? It is, and it isn't.

Apple already uses sapphire glass for the iPhone's camera and the iPhone 5s' TouchID home button with the fingerprint sensor. But Apple's partnership with sapphire manufacturer GT Advanced Technologies has many thinking sapphire will make its way onto the front of the iPhone 6.

There are several things to note, however. Apple's partnership with GT Advanced does make it easier to produce sapphire, but it is still more expensive and, in some ways, more brittle than Corning Gorilla Glass. An Engadget piece shows how many manufacturers are hesitant of jumping to sapphire, given the lack of significant benefits.

"The cost and supply aren't where we'd like them to be for sapphire to be practical just yet," Ken Hong, global communications director for LG, told Engadget. "Sapphire's durability and scratch-resistance are certainly attractive, but Gorilla Glass isn't going to be displaced anytime soon."

Sapphire is an incredibly strong material, coming in with a hardness of 9 out of 10 (diamonds are 10) on the Mohs scale, but there don't seem to be too many reasons to use sapphire other than as a marketing gimmick. It's possible that sapphire displays will be used in smartwatches, such as the iWatch, before they make their way onto smartphones.

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