Birthstone: July

Hardness: 9

Perhaps no gemstone has been as prized throughout history as the ruby. Celebrated in the Bible and in ancient Sanskrit writings as the most precious of all gemstones, rubies have adorned emperors and kings and inspired countless legends and myths with their rich, fiery hues. As the ultimate red gemstone, rubies have symbolized passion and romance for centuries.

Also the color of blood, the stone is symbolic of courage and bravery. Warriors were said to have implanted rubies under their skin to bring them valor in battle and make them invincible. The stone has also been used as a talisman against danger, disaster, to stop bleeding, and a number of other ailments. Its intense color was thought to come from an undying flame inside the stone - or, as some legends would have it, a piece of the planet Mars.

Ruby is the red variety of corundum, a sister of sapphire. It is the second hardest material known after diamonds.

The most valuable rubies come from Myanmar (formerly Burma), but they are mined throughout Southeast Asia. Good quality stones come from Thailand, Sri Lanka, and Vietnam. Kenya and Tanzania also are becoming more important as mining sources for ruby.

The most important factor to consider when buying a ruby is its color. It comes in a variety of shades ranging from purplish- and bluish-red to orange-red. Like sapphire, there is also a translucent variety of ruby that can display a six-point star when cut in a smooth domed cabochon cut.

After color, the factors that influence value are clarity, cut and size. Rubies that are clear with no visible inclusions are more valuable than those with visible internal flaws.

Rubies are rarely found perfect in nature - which is why many are heat-treated to intensify or lighten their color or improve their clarity. Heat enhancement is a permanent, stable process. Some rubies also have surface fractures and cavities that are filled with glass-like materials to improve their appearance. This filler may break, fall out or wear out over time if exposed to heat, strong abrasives or constant impact. For both treated or untreated stones, the safest cleaning method is to just use soapy water or a mild commercial solvent and a brush.