The much-rumored sapphire display cover for the upcoming iPhone 6 may be limited only to the highest-end models, according to new information.

With so many leaks and rumored related to the iPhone 6, however, it can get confusing, so let's start with the beginning. Apple is expected to launch two new iPhone 6 models this year, one with a 4.7-inch display and the other with a larger 5.5-inch screen. The company is also expected to use an extra durable sapphire display cover, but it remains to be seen which models will get this special treatment. Early rumors suggested that only the 5.5-inch iPhone 6 will get the sapphire glass cover, but not too long ago some neat videos surfaced showing a 4.7-inch iPhone 6 model with sapphire glass display. The videos in question showed off just how durable the display was, as it was able to withstand key scratches and even stabbing.

Fast forward to present date, and a new note to investors from JPMorgan Securities claims that Apple will not be able to produce enough sapphire displays for the iPhone 6 launch. This note surfaced courtesy of Taipei Times (via GforGames).

According to JPMorgan, Apple will likely have up to 10 million sapphire glass covers for either 4.7- or 5.5-inch iPhone 6 models, but the company is expected to increase sapphire glass production in the future.

"With the limited disclosure about the iPhone 6 by Apple and amid persistent speculation about the new phone's cover glass adoption, JPMorgan believes the volume will be about 10 million covers this year in either 4.7-inch or a 5.5-inch models, according to the brokerage's latest industry report, released on Tuesday," Taipei Times reports. "The volume of sapphire cover adoption represents less than 1 percent of the entire smartphone market, JPMorgan said."

"'Sapphire covers will also be restricted to high-end iPhones, possibly the 128GB [gigabyte] ones,' the brokerage said in the report," as cited by Taipei Times. "We believe this will mark only the beginning of sapphire smartphone cover adoption."

JPMorgan is reportedly making these estimates based mainly on low yield rates and production costs. The company believes that Apple will not be able to remove Gorilla Glass covers altogether from its iPhone 6 lineup. JPMorgan further notes that it expects production output for sapphire glass covers to be low, as the new cover material will pose various challenges.

According to the firm, yield rates could be below 50 percent and finished sapphire smartphone covers may cost as much as $40 to $45, while finished Gorilla Glass costs $10.

Lastly, JPMorgan further noted that based on their inquiries with sapphire companies such as Apple partner GT Advanced Technologies, as well as Sapphire Technology Co and Procrystal Technology Co, Apple's iWatch may not boast a sapphire display cover, as previously rumored.

As always, however, keep in mind that it's all in the rumor state until official confirmation. This means that nothing is certain just yet, so make sure to take all such reports with a grain of salt.