Gem FAQS > Corundum > Sapphire- Blue
Sapphires come every color of the rainbow except for red in which case they are called ruby. The section deals with blue sapphires.
Sapphire is a corundum (Al2O3) and owes it's color to minute traces of Titanium and Iron. Too much Iron will make a sapphire look black but is actually a super-saturated blue green.
The ideal color of a sapphire should be a balanced medium blue with no trace of green but not too light nor too dark.
99.9% of all sapphires are enhanced by man in some way. The most common enhancement is prolonged heating done in kilns at temperatures of around 600o Celsius. This heat treatment can lightensapphires that are too dark making them marketable, but not always desirable. Heat treatment affects the internal structure of a gemstone and can create tiny halo fractures surrounding inclusions. Sapphires can also be diffusiontreated with titanium to make a sapphire appear blue and to create a star sapphire, but this treatment is only skin deep and is not at all durable.
The finest and most coveted sapphires are from Kashmir and were mined on the what is now the border between Pakistan and India, but the deposits have been depleted. Kashmir sapphires are a velvety royal blue often described as cornflower blue and, due to very fine "silk" found in most of them, have a soft inner glow.
The sapphires from Myanmar (Burma) are the next rarest and most expensive sapphire and are usually a medium dark Royal blue hue.
Last updated on July 19, 2009 by Francis M Lynch