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TourmalineBack to A - Z IndexChard 24 Carat Home Page

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Tourmaline
Tourmaline is generally thought of as green, but can be almost any colour, indeed some tourmalines display two or more colours within the same crystal. Because of the naturally occuring shape, tourmalines are often cut as long baguettes, emerald cuts, or ovals. Large size tourmalines are more relatively common compared with other gemstones, so they are ideal for large jewellery pieces. As with all gemstones, the most attractive colours and qualities are more expensive than lower qualities, and large desirable pieces are not cheap.

Colour
Tourmaline exists in more colours than any other gemstone. The most common colour is a dark green, but bright green chrome tourmalines are seen, as are blue, red, pink, orange, yellow, colourless, brown, violet and black.

Chatoyancy
Chatoyancy or chatoyance, literally from French means cat's eye. Seen best in cat's eye chrysoberyl, but also found in a few other gemstones including tourmaline.

Technical Information
Chemical Composition and Name  - Complex Aluminium Borosilicate
Hardness7.0 to 7.5
Refractive Index1.616 - 1.634 to 1.630 - 1.652
Bi-refringence0.014 to 0.021
Other Optical PropertiesUniaxial
Optic SignNegative
Specific Gravity3.02 - 3.26
Crystalline SystemTrigonal


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