M603 - Sapphire specimens from Madagascar.

The name Sapphire comes from the Greek word sappheiros, meaning "blue stone". It is a gemstone variety of the mineral corundum, an aluminum oxide, when it is a color other than red or dark pink; in which case the gem would instead be called a ruby, considered to be a different gemstone. Sapphire can be found in different colors such as blue, yellow, pink, purple, orange or a greenish color.

Sapphire has a hardness of 9.0 on the Mohs hardness scale. Non gem quality corundum is widely used as an abrasive because of its hardness. The gemstone sapphire is considered a Precious gemstone, along with ruby, emerald, and diamond. Today it is common practice for sapphires to be heat treated in order to enhance their color.