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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
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 is 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), clevelandite,
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. Some tourmaline bearing mica
schists may have formed by regional metamorphism of argillaceous sediments containing
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 the 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
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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