Color–Change Sapphires are Sapphires that change color due to exposure to different light conditions. Some display faint changes while others display strong changes, to incandescent or fluorescent lights. One type changes from green to red and the other Blue to Reddish Purple, and the value of the gem depends upon the strength of change.
Sri Lanka is well known for the finest quality sapphires and come in a range of colors. Mining continues from ancient times to this day. Sri Lanka is known for producing the finest and largest sapphires in the world.
Top-quality sapphires are extremely rare. Beauty, magnificent colour, transparency, and durability are the main features. Color determines the value of a sapphire. The most valuable colors for blue sapphires are violetish blue. Highly saturated medium or dark medium tones are best. Sri Lanka : is well known for the finest quality sapphires, and the largest sapphires in the world. < See list of World Famous Gems >
Sapphires and rubies are both members of the corundum family with the same hexagonal crystallographic structure. The basic chemical formula is AL 2 2O 3 .. the same for both ruby and sapphire. It is the presence of trace elements like chromium, iron, vanadium and titanium which are responsible for the wide range of colors in which the mineral occurs. When a corundum is red, it is known as a ruby and any other color is a sapphire. In practice however, the determination is not always so straightforward because there are no internationally accepted standards for the color of a ruby. Gemologists could describe the same stone as a purplish red ruby or a purplish red sapphire and borderline cases are not uncommon.
Sapphires are noted for the large range of colors in which they occur. The name fancy sapphire, is used to describe sapphires which are not blue. Fancy sapphires are available in an amazing range of colors including yellow, green, violet, pink, brown, purple, violet, white, black and orange. 
