Sapphire is a colored variety of Corundum and gets its characteristic color from trace elements or impurities. The most well-known Sapphire color is blue, but Sapphires can also occur in a variety of other colors including pink (Padparadscha Sapphires), yellow, green and orange.
The mineral aluminum oxide (Al2O3) in its pure form is called Corundum. It is one of the hardest natural materials and has a hardness of 9 on the Mohs scale, making it more resistant to scratches than most other gemstones.
While the colorless Corundum is mainly used for technical purposes, Sapphire is a sought-after jewelry and collector's stone.