All gem quality corundum, which are not red, are known as sapphire except Padparadscha, which is the second only variety of corundum, which is given its own name as Ruby being the first one. Corundum without impurities is known as colorless sapphire, also known as white sapphire.

Locations:

Pure colorless (white) sapphire is found in Sri Lanka. The cloudy or milky colored sapphire is also found in Sri Lanka, which is locally called as “geuda”. When geuda is heated it produces blue sapphire.

Chemical Composition: Aluminum Oxide
Crystal Structure: Trigonal
Hardness: 9
Specific Gravity: 4
Refractive Index: 1.76-1.77
Colors: Colorless or white.
Luster: Vitreous

Astrological Relevance:

Being sapphire, colorless (white) 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).