The value factors: the art and science of pricing tourmaline.

As with all transparent gemstones, color, cut, clarity and carat weight combine to determine a stone's value. With tourmaline, these factors vary slightly depending on which variety you are looking at. Therefore, it is always a good idea to compare different types separately. Below is a list of common valuing factors and the variations depending on type.

Color: In general, you are looking for rich, full-bodied uniformity of color. Examine each stone from the top, bottom and profile over various backgrounds and under numerous light sources. This test will reveal the hue of the stone, consistency of color, particular overtones as well as inclusions (internal flaws) which could block color and, or, threaten durability. Don't confuse any red stone with the far more costly rubellite, or blue and green for paraiba or chrome. Also, if you are looking at bi or tri-colored stones, make sure the distinction between the colors is strong and vivid.

Clarity: With all gemstones, clarity is the term for how free from flaws a stone is. Most types of tourmaline are available "eye-clean," so you should be able to find high quality stones in just about any color you like. The red group, however, tend toward much lower clarity than others. Your expectations for red tourmaline should alter accordingly. There are some excellent red stones on the market, though. So, if red is the color you've got your heart set on and you want top quality, you will need to be a little more patient, and expect to pay the price when your dream stone comes along.

Cut: Tourmaline is cut in a variety of unique styles, ranging from unusual fantasy (three dimensional carving) cuts to more traditional facet cuts. Cat's eye's are cut in cabochon (dome shape) ovals to highlight the special effect. Many tourmaline, particularly the multi-colored varieties are cut in long rectangular bars to show off the distinct zones of color in the natural growth patterns of the crystal. Pick any cut you like, but remember that more complicated styles that sacrifice much of the rough stone will bring a higher per-carat price.

Carat weight: A carat is a carat is one-fifth of one gram. With all gemstones, you want to get in the habit of thinking in terms of price-per-carat, rather than total cost of a stone, as there are too many factors contributing to the per-carat cost of each stone to make a general price for each type. Beware of "total weight" price tags. You want to know the price-per-carat of the stone prior to mounting so you don't pay paraiba (up to $10,000 per carat) prices for gold settings.

Treatments: Almost all tourmaline has been heat treated for color enhancement. Although this treatment is fully acceptable due to the success of permanent color and clarity improvement, there is the possibility that it makes the stones slightly more brittle.

Some tourmaline is also irradiated for color and clarity enhancement. This process is more common in the red and yellow varieties and the radiation levels are totally harmless. For many gemstones, irradiation is not a permanent enhancement. Tourmaline accepts this process much more readily and the treatment is considered stable in the trade. Overexposure to heat, however, may cause the enhanced color to fade. But the color can be restored with another treatment.

Always ask your jeweler what treatments have been performed on your stone and get such work clearly stated on your bill of sale.