Sapphire is a variety of the mineral species corundum. Contrary to popular belief, not all Sapphires are blue. Although blue is the most common color, the range for sapphire is vast and can include yellow, pink, purple, orange or green. All colors of corundum except for red are sapphires; red corundum is classified as Ruby. Not only are Sapphires beautiful, but also extremely durable and valuable. Sapphires have been known to be used in watch crystals, high-durability windows and infrared optical components. Sapphire is the birthstone for the month of September.