optical parts - Sapphire,ruby parts

Sapphire is a single crystal aluminum oxide (Al2O3). Its Mohs hardness is 9, it is one of the hardest materials. Sapphire, is resistant to attack by strong acids due to its high dielectric constant. It has high compressive strength and a high melting point. It is also resistant to UV radiation darkening. Sapphire optical windows are ideal for applications where high pressure, vacuum, or corrosive atmospheres are a consideration.