A ruby is a pink to blood-red colored gemstone. It is a variety of mineral corundum or aluminum oxide.
Presence of the element Chromium causes the red color. Its name comes from ‘ruber’- the Latin word for red. Other varieties of gem-quality corundum are generally called as sapphires.
The ruby is considered one of the four most precious stones along with sapphires, emeralds and diamonds.
Prices of rubies are primarily determined by color. The brightest and most valuable “red” called pigeon blood-red, commands a huge premium over other rubies of similar quality.
After color follows clarity: similar to diamonds, a clear stone will command a premium, but a ruby without any needle-like rutile inclusions may indicate that the stone has been treated.
The Color, the Clarity, the Cut and the Carat weight determine the price of a gem stone.