With Apple's tradition of keeping future product details quiet, hard evidence is hard to come by, but Apple Insider has done just that.

While it may be no secret that the tech giant bought a sapphire plant in Arizona, Apple Insider has learned that a related patent filing was just approved. The patent document calls for "Oleophobic coating on sapphire," which means Apple is seriously considering using sapphire for its display screen.

The patent, approved Thursday, lists the use of sapphire for iPhone, iPad and other mobile device screens. Apple has supposedly taken an interest in sapphire because of the factory's location in America and because it will make the screens resistant to scratches and smudges.

Aside from the patent document, here are more rumors regarding the upcoming iPhone, presumably titled the "6."

Nikkei reported that Apple will once again release two phones at once, but did not specify what each would be called. They will, however, be different sizes and released in September.

"The new phone, expected to be called the iPhone 6, will likely be offered in 4.7- and 5.5-inch versions, both of which are larger than the current generation's 4-inch screen," Nikkei reported.

"Manufacturers have apparently begun making such components as fingerprint sensors and chips for liquid-crystal drivers."

According to DigiTimes, Apple has placed battery orders with Simplo Technology in Taiwan and Shenzhen Desay Battery Technology in China, but not with the company that distributed the iPhone 5 and 5C batteries. The report is an indication that Apple is preparing for a release date in the coming months. While some reports have said Apple may be considering a summer release for the iPhone 6, others have said the company will stick to its tradition and release it in the fall.

AppAdvice has learned of a new iPhone 6 concept that makes the new smartphone look like a larger version of the iPod Nano. The concept comes from Martin Hajek in collaboration with iCulture.nl and has predicted the iPhone 6 to have a larger screen, a width slightly thinner than the iPhone 5 and a boxy frame.