Ruby
Ruby is a red color variety of corundum mineral, it Is «brother» of sapphires in chemical composition and structure. The best untreated samples can compete in price with very expensive colored diamonds. Ruby is considered the most valued gemstone. On auctions the best samples cost over 1 million USD per carat. Ruby is a corundum mineral colored with chrome and possess red color with pink, orange and violet shades. Pure spectral red color without additional shade is the most valued. In commerce the expression «Pigeon Blood» can be used for description the best bright red color. This color can also be specified in a certificate.