Chemical Composition: Aluminium Oxide, Al 2 O 3
Refractive Index: 1.76 – 1.78
Specific Gravity: 3.80 – 4.05
Crystal System: Trigonal
Moh's Hardness: 9
Sapphires are apart of the Corundum family and come in varying shades of blue and is coloured by iron and titanium. Heat treatment is also common in blue sapphires to improve the colour and to rid of the striations.
Diffusion treatment is another common treatment, this is achieved by coating the surface of the stone with aluminium oxide and penetrates the stone a fraction of a millimeter to improve colour.
Common localities include India, Burma, Thailand, Australia, Sri Lanka (Ceylon)