Ruby is one of corundum with its red color. Ruby is considered one of the four precious stones, together with blue sapphire, yellow sapphire and pink sapphire. Its red color originated from Chromium. A colored element that provides many shades of color such as pinkish red, purplish red, orangey red. Vivid red which referred as the most beautiful color. In Thailand gemstones sellers will call ruby as “red gem”. Ruby has been dubbed as the “ King of Gems ” and rubies are believed to help protect the owner from the bad luck. Because of its beautiful and strong red colors , ruby are more popular than other red gems in making jewelry.

Property of Ruby

Chemical composition : Al2O3, Aluminium oxide

Crystal system : Trigonal

Refractive index (RI) : 1.76-1.77

Specific gravity (SG) : 3.80-4.05

Birefringence : 0.008-0.010

Optical nature : (DR) uniaxial

Luster : Vitreous

Hardness : 9

Colour : red, pinkish red, purplish red, orangey red (Its red color originated from Chromium.)

Localities : Thailand, Burma, Vietnam, Afghanistan, Cambodia, Pakistan, Sri Lanka, Tanzania

Ruby generally is an unclear gem because it contains several inclusion, if it is bright red with a few fractures inside,this ruby is often polished into faceted, but if it is dark with lots of fractures inside, this ruby is polished into cabochon.

Picture : Faceted cut and Cabochon ruby.


Ruby quality improvement enables to be done by heat treatment for its explicit color, sparkling and shining.Ruby that has lots of inclusions inside is often improved by heating process. This procedure incurs brightness to its surface, and decreases inclusion.

Picture : Rough Ruby