Manufactured sapphire is synthetic crystalline aluminum oxide that is transparent like glass, but harder. On the Mohs mineral hardness scale of 1 to 10 (going from softest to hardest), sapphire (a form of corundum) scores 9. Ordinary glass scores 6 to 7 and diamond scores 10.
Sapphire is transparent, durable, and scratch-resistant. Because of these qualities, hardware vendors have expressed interest in it as a replacement for glass in tablet PC and smartphone displays. The glass in such screens is known for breaking easily if the device is dropped. Manufactured sapphire display coverings could offer superior physical ruggedness. The main drawback is the fact that sapphire is expensive to manufacture.
A product from Corning called Gorilla Glass offers another alternative to ordinary glass in tablet and smartphone displays. Like manufactured sapphire, Gorilla Glass offers excellent durability and scratch resistance. In addition, Gorilla Glass can be manufactured at far lower cost per kilogram than sapphire.