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.

Locations:

It is mainly found in Sri Lanka. Other localities include Australia, Thailand, Montana (USA) and East Africa.

Chemical Composition: Aluminum Oxide
Crystal Structure: Trigonal
Hardness: 9
Specific Gravity: 4
Refractive Index: 1.76-1.77
Colors: Shades of yellow.
Luster: Vitreous

Astrological Relevance:

Being sapphire, yellow 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).