The lady of the three some commonly known as “precious gemstones” , ruby part of the corundum family. It exhibits a range of red colors, and the most desired color is "pigeon's blood" red (pure red with just a hint of blue). On Mohs' scale of hardness, ruby ranks a hard 9. It has a strong, adamantine ("diamond-like") luster. Often used in gem pieces made for royalty around the world.