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Tourmaline is the name given to a group of related minerals all having essentially the same crystal structure but varying considerably in chemical composition and in some of their physical properties. It is best described as a very complex aluminum borosilicate.
There are eleven distinct mineral species of tourmaline based on chemical composition: buergerite, chromdravite, dravite, elbaite, feruvite, foitite, liddicoatite, olenite, povondraite, schorl and uvite.
Tourmaline occurs in all colors. Commonly used names have been given to tourmalines of specific colors or color combinations such as rubellite tourmaline for pink to red shades, indicolite for blue tourmaline, and watermelon tourmaline for tourmalines showing concentric color zoning with pink-red cores surrounded by green. Since some species of tourmaline such as elbaite and liddicoatite can look exactly the same and laboratory analysis is necessary to determine the precise tourmaline species, the generally preferred nomenclature today for tourmalines that have not been lab analysed is simply to use the color of the specimen as a prefix followed by tourmaline as in green tourmaline.
The color in tourmaline is due to the presence of metal ions (Fe, Mn, Cr, V, Ti and Cu) in its crystal structure. The color we see in tourmalines is produced when light is absorbed by these ions or by interactions between these ions (intervalent charge transfers).
Some tourmalines form with inclusions of thread-like tubes or cavities which usually occur parallel to the length of the crystal. If these inclusions occur in sufficient number, they may produce a chatoyant effect that yields a cat's-eye when cut into a cabochon gem.
Tourmaline forms in a variety of geologic settings. It occurs most often in granite pegmatites and in their immediate vicinity in the enclosing host rocks. Pegmatitic tourmaline is commonly black and typically occurs as large black tourmaline crystals associated with microcline, albite, quartz and muscovite. The light colored gem tourmalines are much more rare, usually occuring in pegmatite core zones with quartz (often as smoky quartz), cleavelandite, muscovite, lepidolite, and more rarely with amblygonite and spodumene (variety: kunzite).
Other occurances for tourmaline are: with quartz in hydrothermal veins where heated mineral bearing liquids or gases from deep igneous sources later cooled and crystallized along rock fractures, in granites due to late stage alteration of micas and feldspars by boron containing fluids, and by boron metasomatism in contact and regionally metamorphosed rocks yielding large black tourmaline crystals in schist matrix. Some tourmaline bearing mica schists may have formed by regional metamorphism of argillaceous sediments containing evaporite borates.
Because of tourmaline's relatively high hardness and specific gravity, it is often found in eluvial and aluvial deposits.
Tourmaline is usually recognized by its rounded triangular basal sections, color, lack of cleavage and conchoidal fracture.
Transparent specimens can often be distinguished by their strong pleochrism/dichroism.
The name tourmaline is of the Sinhalese turmali which was originally applied to an assortment of colored stones being mainly zircons. Buergerite was named after Professor Martin J. Buerger, a well known research scientist and crystallographer. Dravite was named after the Drave region in Carinthia. Elbaite was named after the isle of Elba in Italy, and liddicoatite was named after Richard T. Liddicoat of the the Gemologial Institute of America. Schorl is an old German mining term for gangue minerals. Uvite is named for the Uva district in Sri Lanka.
Tourmaline gemstones are widely used, occuring in all colors. Tourmaline also has many scientific and technological uses due to the fact that an electrical charge can be induced in some tourmaline crystals simply by applying pressure to the crystal in the direction of the vertical crystal axis. This effect is known as piezoelectricity, and has many uses in pressure measuring equipment and other scientific applications. Some tourmalines also show pyroelectricity, which occurs when the crystal is heated yielding a positive charge at one end of the crystal and a negative charge at the other.
Tourmaline is a traditional birthstone for the month of October. The astrological sign of tourmaline is Libra.
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Tourmalines are said to enhance one's understanding, increase self-confidence and amplify one's psychic energies. They also are said to neutralize negative energies, dispell fear and grief, and to aid in concentration and communication. Tourmalines are also said to be usefull in relaxing the body and the mind, and to help in the treatment of infectious diseases, anxiety, blood poisoning, arthritis and heart disease.
Some of the metaphysical properties for the specific colors of tourmaline are given below: Black Tourmaline: said to absorb and give protection against negativity from both people and electrical & magnetic fields. It is also said to sharpen one's wits, to enhance vitality and to give emotional stability. Blue Tourmaline: said to enhance one's communication skills, intuition and spiritual perspective. Green Tourmaline said to give success, prosperity and peacefull sleep. The use of pink tourmaline jewelry is said to inspire love, spirituality and creativity. Wearing pink tourmaline earrings or jewelry is also said to give wisdom and enhance one's willpower. Watermelon Tourmaline: said to be very effective in helping one to recover from emotional problems. Also all the properties of pink & green tourmalines.
For more in-depth metaphysical information, see our Metaphysical Books section.
This is the end of our Tourmaline Factsheet and Information page.
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