The classic ruby is a deep, rich red, although the stone appears in varying shades from pink to purple to brown, depending on it's chemical makeup. In terms of hardness, rubies are second only to diamonds, which, along with their vibrant color, makes them highly prized for making jewelry.

At the time of the Borgias (15th-16th centuries), rubies were though to counteract poison, and therefore in high demand.

In the middle ages, the ruby was seen as a prophetic stone. People believed it would darken when its wearer was in danger.