Sapphire is the most precious and valuable blue gemstone. It is a very desirable gemstone due to its excellent color, hardness, durability, and luster. In the gem trade, Sapphire without any color prefix refers to the blue variety of the mineral Corundum. However, the term Sapphire encompasses all other gem varieties and colors of Corundum as well, excluding Ruby, the red variety of Corundum, which has its own name since antiquity. The most valuable color of Sapphire is a cornflower blue color, known asKashmir Sapphire or Cornflower Blue Sapphire. Another extremely valuable Sapphire form is the very rare, orange-pinkPadparadschah. An exotic type of sapphire, known as Color Changing Sapphire, displays a different color depending on its lighting. In natural light.