Ruby is a pink to blood-red colored gemstone, a variety of the mineral corundum. Other varieties of gem-quality corundum are sapphires, which come in every color of the rainbow. The word ruby comes from ruber, Latin for red.
Ruby is 9 on the Mohs hardness scale making it a superior gemstone for jewelry. In fact, ruby’s rich red color is deserving of it’s nickname, the “King of Gems”.
The quality of a ruby is determined by its color, cut, and clarity, which, along with carat weight, affect its value. The brightest and most valuable shade of red called pigeon blood, commands a large premium over other rubies of similar quality.