All gem quality corundum, which are not red, are known as sapphire except Padparadscha, which is the second only variety of corundum and has been given its own name as Ruby being the first one. The blue variety of corundum is known as blue sapphire as its color suggests. The blue color in blue sapphire comes from the impurities of iron and titanium. The most valuable is the clear deep blue color. There is a variety of cloudy or milky colorless sapphire found in Sri Lanka, which is locally called “geuda”. When geuda is heated, it produces blue sapphire.

Locations:

Gem quality sapphire is found in Burma, Sri Lanka and India. The best Indian blue sapphire comes from Kashmir, which exhibits cornflower blue color. Dark blue sapphires come from Nigeria, Thailand and Australia, which can appear nearly black. An attractive metallic blue color comes from Montana, USA. Other localities are Brazil, Colombia, Malawi, Kenya and Cambodia.

Chemical Composition: Aluminum Oxide
Crystal Structure: Trigonal
Hardness: 9
Specific Gravity: 4
Refractive Index: 1.76-1.77
Colors: Light blue to deep blue to black.
Luster: Vitreous

Astrological Relevance:

Being sapphire, blue sapphire is considered to be one of the birthstones for the month of September, which covers two zodiac signs: Virgo (August 22 To September 22) and Libra (September 22 To October 23).