Even though sapphires, rubies and emeralds differ in color and weight for example, there is a consistency in how they are valued. And that includes lesser known gemstones like tourmaline, alexandrite, peridots, and garnets as well. The four characteristics that determine value in a colored gemstones are color, clarity, cut, and carats, but the most important is color, color, and more color.

The intensity of the color and the closer it comes to the true spectral color means the stone has more value. Emeralds should be a pure green, rubies the reddest red, and sapphires a deep rich blue. As the color varies from the spectral ideal, the value declines. For example: Burmese rubies have the best color. Rubies that are a lighter red, reddish orange, or with a touch of brown or a bit of blue aren't nearly as valuable.

Color is measured in intensity or saturation, in other words the vividness of the color. It also reflects the hue, or how close the color approximates the pure spectral color; tone which is how light or dark ie., how much black or white is in the color; and finally the distribution of the color or how even the color is across and within the stone.

The other factors of clarity, cut, and carats are not as important to the value of a stone that has the best color and inversely have a greater impact on the value of a stone that is not as pure a color.

Clarity is the absence of internal flaws that can be seen with a magnification of 10. Most colored gemstones naturally have inclusions or flaws. A prime example are emeralds which very rarely don't have flaws. The lighter the color of the stone the more visible the flaws become, while the darker the color of the stone the less obvious. The type of flaw and where it occurs in the stone affects its value as well.

Cut is the way a stone is faceted to bring out the best characteristics of that particular stone for its type. The cut brings out the color, fire, and brilliance of the stone, not sacrificing one for the other. Unlike diamonds colored gemstones can also be presented as a smooth rounded surface known as cabochon cut. Cabochon cut sapphires and rubies often reflect a star and are known as star sapphires and star rubies.

Carat is the weight of the stone, not how big it is. Different types of gemstones have different weights when cut to the same size. The density of rubies is greater than the density of emeralds so a one carat ruby will be smaller than a one carat identically cut emerald. Stones can be cut to look bigger as well. Some gemstones are more readily available in larger weights such as amethysts or tourmalines, that say emeralds. For example: An 18 carat tourmaline will have a lesser value per carat than a 5 carat alexandrite because large tourmaline stones are more common than large alexandrite stones.

The best safety precaution when buying gemstones or gemstone jewelry when shopping online, is to buy from a reputable jeweler. You will get what you pay for.