This article is about the mineral or ruby red orange. Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sapphires.

Some gemstones that are popularly or historically called rubies, such as the Black Prince’s Ruby in the British Imperial State Crown, are actually spinels. These were once known as “Balas rubies”. 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 blood-red or pigeon blood, commands a large premium over other rubies of similar quality. Rubies have a hardness of 9. 0 on the Mohs scale of mineral hardness.