Whispering Pines

Sapphire is a gemstone variety of the mineral corundum, the crystalline form of aluminium oxide (α-Al2O3). Pure corundum is colorless, while trace elements in its crystal structure produce a wide range of colors. Blue is the best-known, but sapphires also occur in yellow, green, purple, pink, orange, gray, black, and colorless forms. Red gem-quality corundum is classified as ruby rather than sapphire. The boundary between ruby and pink sapphire is based on color appearance and varies among gemological and trade conventions. Sapphire has a Mohs hardness of 9, making it highly resistant to scratching and abrasion.