Vertu COO Perry Oosting told the site that Apple investigated the possibility of a sapphire display and recruited some of its employees to work on the project. Vertu makes luxury cell phones some of which have sapphire displays.
MacRumors notes that at least two Vertu employees have joined Apple in the last year.
Apple ultimately shelved the sapphire project because the material is unsuitable for production in the numbers that Apple requires at the current point in time. Corning, the company that manufacturers Gorilla Glass 3 for Apple's displays, has also stated that sapphire is an inferior option for mobile displays. The company believes that Gorilla Glass offers greater strength, lower weight, less energy cost in production, and lower pricing; all important features for mass manufactured products.
While Apple has opted against sapphire crystal displays, it does use the material as a cover for the rear camera lens to prevent scratches from affecting your photos. Additionally, the iPhone 5S is rumored to feature a sapphire crystal capacitive touch home button with integrated fingerprint scanner.