Sapphire, a variety of the mineral corundum, is usually considered to be blue, but in fact it occurs in a wide range of colors except for red. That's because the gem industry uses the name ruby for red corundum, in recognition of the special value we attach to the hardest of all red gemstones.

Blue is such an important color for sapphire that the term sapphire in the gem trade always refers to blue sapphire. Other colors of sapphire are called fancy sapphire, and the colors include pink, yellow, orange, green, violet and white. The wide range of colors in corundum is caused by different impurities such as chromium, titanium and iron.

Among the fancy sapphires, yellow has been especially valued, in large part because of its place as one of the nine planetary gems in the Vedic astrological tradition. Green sapphire was once thought of as one of the less desirable colors, but is now increasingly popular, though no one is quite sure why. Perhaps it is because green has always been an important gemstone color (think emerald, tourmaline and tsavorite garnet) and green sapphire is fairly rare.

Green sapphire can occur in colors ranging from a light mint green to a dark forest green. The finest green sapphire is thought to come from Sri Lanka, but they are very rare indeed. Most of the green sapphire you will see in the market are from Thailand or Australia. These tend to darker green and are often blue-green or yellow-green. Green sapphire may also be found from Burma and Madagascar.

Green sapphire is colored by traces of iron. In some cases the green color of due to the presence of both blue and yellow bands, which make the gem appear green to the eye. But the color zoning is obvious under magnification, and can sometimes be seen with the naked eye.

Though there are many choices in green gemstones, the excellent gemstone characteristics of corundum make green sapphire a popular choice, especially for rings. You will find interesting pieces in both faceted and cabochon styles. Green sapphire, like sapphire in other colors, is typically heat treated.