Single crystal sapphire has a unique combination of excellent mechanical, thermal, chemical, and optical properties. It retains its high strength at high temperatures. It is also chemically inert to common acids and alkali even at elevated temperatures. Combined with its wide transmission range from ultraviolet to infrared, it is the ideal material for optical components used in hostile environments. High thermal conductivity at cryogenic temperature is one of the outstanding features of sapphire as well.
Second only to a diamond in hardness, sapphire is extremely durable and scratch & wear-resistant. It is often used in making parts and components for hard-wearing applications requiring a high level of scratch resistance.