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TOURMALINE
      No other gemstone offers buyers a wider variety of colors than tourmaline. Besides being found in every color of the rainbow, tourmaline may also be multicolored in one piece. Some of the species and varieties of tourmaline are listed below:

GREEN TOURMALINE : This variety is plentiful and comes in a wide range of shades. It tends to appear very dark and nontransparent in one direction. To lighten and improve the color, green tourmaline is commonly heat-treated. Stones that are blackish and yellowish  are the least expensive. Those with an intense green color resembling a good emerald cost the most.
 Top-color green tourmalines are found in Tanzania and are called Chrome tourmalines. Eye-clean green tourmaline is readily available. Therefore, good-quality stones are expected to have a high clarity. Top quality chrome tourmaline can retail for as much as $2000 per carat. Most green tourmaline, however, is quite affordable, with retail princes ranging from about $20 in very low qualities to $400 per carat in better stones

PINK or RED TOURMALINE : The discovery of pink tourmaline in southern California in 1898 helped popularize this stone. Red and pink tourmaline are also mined in Afghanistan, Brazil, Nigeria and Madagascar. RUBELLITE is a trade name applied to red tourmaline. True-red rubellites often have a low clarity. Clean rubellites with a strong red color can wholesale for over $1000 per carat.
 Pink and red tourmalines from areas other than Nigeria are commonly irradiated to intensify their color. The stones are not radioactive and the color is relatively stable. However, strong heat like that from a display window or a jeweler’s torch can cause the color to fade. Sometimes rubellite is treated with fillers to improve its clarity. Even when treated, you should expect it to have a lower clarity than other transparent tourmalines.

BLUE TOURMALINE (INDICOLITE or INDIGOLITE) : Indicolite comes in various shades of blue, but frequently, it’s a dark greenish or grayish blue. The color is often lightened with heat treatment. A brighter turquoise-blue material has been found in Northeastern Brazil in the state of Paraiba. It’s called Paraiba Tourmaline and is the rarest and most expensive tourmaline. In its finest qualities, it has wholesaled for over $10,000 per carat. Paraiba tourmaline can also have an intense green or violet color. Don’t expect to find it in your local jewelry store. Indicolite costs less, ranging in price from about $100 to $800 retail per carat.

YELLOW, ORANGE, BROWN or GOLDEN TOURMALINE : Yellow and orange tourmaline occur naturally but are sometimes produced by irradiating light yellow or green tourmaline. Heat can may retail for about $30 to 350 per carat.
Brown tourmaline tends to be less expensive.

BI-COLORED or MULTI-COLORED TOURMALINE : The pink and green variety is the most common type, but stones can also be pink and colorless or blue and green. Some stones have more than two colors. The most valued stones have distinct saturated colors with sharp boundaries and no fractures. Green and pink slices of crystal tourmaline the have concentric color banding are called watermelon tourmaline.

CAT’S-EYE TOURMALINE : This is found in a variety of colors but pink and green are less difficult to find than red or blue colors. Cat’s-eye tourmaline is occasionally treated with epoxy fillers to improve transparency and seal the tubes causing the cat’s-eye. The fillers prevent dirt from entering the tubes.

Care Tips : Clean tourmaline with warm soapy water. Ultrasonics are considered risky for this stone. Avoid strong heat because it may alter the color; sudden temperature changes may also cause fracturing. Tourmaline does not react to chemicals. It’s normally stable to light, but some irradiated stones may fade with prolonged exposure.