Sapphire is the most precious and valuable blue gemstone. It is a very desirable gemstone due to its excellent color, hardness, durability, and luster. In the gem trade, Sapphire without any color prefix refers to the blue variety of the mineral Corundum.
|Color||Often blue, but varies|
|Mohs scale hardness||9.0|
|Specific gravity||3.95 – 4.03|
|Refractive index||1.768 – 1.772|