A ruby is a blood-red colored gemstone, a variety of the mineral corundum (aluminium oxide). ... 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. Rubies have a hardness of 9.0 on the Mohs scale of mineral hardness. Rubies are available in almost all shapes, Ruby is one of the most popular gemstones and is used extensively in jewellery. The stone in all forms of jewellery, including bracelets, necklaces, rings, and earrings. It is used both as a centrepiece gemstone in pendants and rings, as well as a secondary stone to complement other gemstones.Rubies were usually drilled as beads and used as pendant gemstones on necklaces, turban ornaments or earrings. They were admired for their color which followed the Persian literary tradition of representing wine and the sun, evoking the light of dusk.