Corundum colored by traces of chromium is red in colour and is called ruby.
If the color is at low saturation, namely of pink color, the corundum is called pink sapphire. The border between pink sapphire and pinkish-red ruby is determined by a Master stone.
Pink SapphirePigeon's Blood
If corundum is colored by iron and titanium in certain oxidation states its colour is blue and is called sapphire.
Mixtures of pink and orange color are described as pinkish-orange, pink-orange or orangy-pink sapphire. Such sapphires are also known in the trade as "Padparadscha". No brown overtones are accepted.
All the other colors of corundum are described as sapphire with its color indicated, such as yellow sapphires, purple sapphire, color changing sapphire (color looks different if viewed in different light sources) or as "FANCY COLORED SAPPHIRES". The origin of color in yellow to orange sapphires as well as "Padparadscha" may be related to a set of trace elements as well as color centers.
Corundum is very durable because of its hardness and commonly enhanced by heat. Unenhanced corundum is scarse. Attention has to be made on new treatments as well as on conventional surface-diffusion treatments (blue colors). Color is stable if not irradiated by treatment techniques. Stability of color must be particularly checked for yellow, orange and Padparadscha colors. See comments in reports.
GRS Color Names for Natural Sapphires, Natural Fancy Sapphires and Natural Rubies
Pigeon's Blood
