Ruby is a red variety of corundum.

At all times red color has been associated with strong emotions, passion and love, power, fire and blood. Therefore, the flame- red ruby is the most popular stone since ancient times. Ruby is mentioned in the Bible. The earliest mention of a ruby is found in Indian manuscripts dated 2300 BC, where it was named ratnaraj, which means "king of precious stones" in Sanskrit. Almost all kings and emperors had excellent rubies in their collections of jewelry. To the present-day price of high-quality rubies is higher than that of diamonds of the same size. The record value of a ruby was recorded at Christie's auction in 2011, where the ruby ring from Elizabeth Taylor' collection was sold at $ 4.2 million.