Sapphire (Hebrew name) is a mono-crystal of alumina (Al2O3), a mineral called corundum. Whilst corundum consists of pure alumina, the sapphires always contain a mixture of other elements (iron, chromium, copper, magnesium, etc.) that supply it with blue, red, yellow, pink, purple, orange or greenish color. Among the sapphires are all gems, which are corundum varieties except red - also called ruby.
Sapphires are characterized by a variety of shapes and processing. The most precious are the oval shapes in which the star effect of the gem stones. Fancy and Emerald Shapes are also common. For less pure sapphires, the shape of the kaboson is used.
Color blue, orange, pink, yellow, green,
white or multicolored
The cranial system
Refractive index 1.762-1.778
Density 3.95-4.03 g / cm³