Sapphire (Hebrew name) is a single crystal of alumina (Al2O3), a mineral called corundum. It occurs either as a natural gem or is artificially manufactured for a variety of different applications, such as its hardness on glass and watch bearings.
While corundum consists of pure alumina, sapphires always contain an admixture of other elements (iron, chromium, copper, magnesium, etc.) which give it a blue, red, yellow, pink, magenta, orange or greenish color. Among the sapphires are included all the gems, which are varieties of corundum - except red - called ruby.
Apart from the blue sapphire, the most valuable sapphire is the "padparascha" - a salmon-colored sapphire, which is often confused with orange and pink sapphire.