Ruby is a highly prized and valuable gemstone that is known for its rich, red color and durability. It is a type of corundum, a mineral made up of aluminum oxide, that contains trace elements of chromium, which gives it its characteristic red color. The intensity of the red color depends on the amount of chromium present in the stone, with those containing higher amounts being more valuable. In addition to its color, ruby is also prized for its durability, ranking a 9 on the Mohs scale of mineral hardness, making it one of the hardest gemstones. It is often used in jewelry, such as engagement rings, necklaces, earrings, and other fine jewelry, and is also popular in traditional and cultural jewelry.