Tourmaline Information
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Tourmaline Crystals
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Tourmaline Information
Tourmaline Information for all of the Tourmaline varieties
Green Tourmaline Earrings
Tourmaline Information Index
Tourmaline Variety Names (and tourmaline products in our on-line store)
Tourmaline Physical Properties
Tourmaline Background Info
Tourmaline Occurance and Diagnostic Features
Tourmaline History and Uses
Tourmaline Metaphysical Properties
TOURMALINE VARIETY NAMES & TOURMALINE PRODUCTS IN OUR ON-LINE TOURMALINE STORE:
TOURMALINE by COLOR |
ITEM CATEGORIES select any link below to enter our Online Tourmaline Store |
Tourmaline Crystals and Tourmaline Mineral Specimens |
Tourmaline Spheres |
Tourmaline Gemstones |
Tourmaline Facet Rough |
Lapidary Rough |
Spectacular Decorator Tourmalines and Rare Collector Quality Tourmalines |
Hand Crafted Tourmaline Jewelery: Tourmaline Bracelets Tourmaline Earrings and Tourmaline Necklaces |
BLACK TOURMALINE |
Black Tourmaline Crystals and Black Tourmaline Mineral Specimens |
Black Tourmaline Spheres |
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Black Tourmaline Lapidary Rough |
Spectacular Black Tourmaline Items and Black Tourmaline Crystals |
Black Tourmaline Jewelry: Black Tourmaline Pendants Black Tourmaline Necklaces Black Tourmaline Bracelets and Black Tourmaline Rings |
BLUE TOURMALINE (INDICOLITE) |
Blue Tourmaline Crystals and Blue Tourmaline Mineral Specimens |
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Blue Tourmaline Gemstones (blue tourmaline gems) |
Blue Tourmaline Facet Rough |
Lapidary Rough |
Spectacular Blue Tourmaline Items |
Blue Tourmaline Jewelry: Blue Tourmaline Pendants Blue Tourmaline Rings and Blue Tourmaline Earrings |
GREEN TOURMALINE |
Green Tourmaline Crystals and Green Tourmaline Mineral Specimens |
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Green Tourmaline Gems |
Green Tourmaline Facet Rough |
Green Tourmaline Lapidary Rough |
Spectacular Green Tourmaline Items |
Green Tourmaline Jewelry: Green Tourmaline Pendants Rings, Necklaces and Green Tourmaline Earrings |
PINK, PEACH, RED and PURPLE TOURMALINE (RUBELLITE) |
Pink Tourmaline Crystals and Rubellite Tourmaline Mineral Specimens |
Rubellite Spheres |
Pink, Purple, Sunset Tourmaline Gems |
Pink, Purple, Sunset Tourmaline Facet Rough |
Pink, Purple, Sunset Tourmaline Lapidary Rough |
Spectacular Rubellite Tourmalines and Fine Rubellite Items |
Rubellite Tourmaline Jewelry: Sunset Tourmaline Jewelry Pink Tourmaline Earrings, and Pink Tourmaline Necklaces |
WATERMELON TOURMALINE |
Watermelon Tourmaline Crystals and Watermelon Tourmaline Mineral Specimens |
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Watermelon Tourmaline Gems |
Watermelon Tourmaline Facet Rough |
Watermelon Tourmaline Lapidary Rough |
Spectacular Watermelon Tourmaline Items |
Watermelon Tourmaline Jewelry |
BI-COLOR and MULTI-COLOR TOURMALINES |
Bi-Color Tourmaline Crystals and Multi-Color Tourmaline Mineral Specimens |
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Bi Color Tourmaline Gems |
Bi Color Tourmaline Facet Rough |
Bi Color Tourmaline Lapidary Rough |
Spectacular Bi Color Tourmaline Items |
Hand Crafted Bi-Color Tourmaline Jewelry |
Go up to the Tourmaline Information Index
- General composition: (Na, Ca)(Li, Mg, Al)(Al, Fe, Mn)6(BO3)3(Si6O18)(OH)4
- Chemical Composition of Ideal Endmember Tourmaline Species
- Buergerite Tourmaline: NaFe3Al6B3Si6O30F
- Chromdravite Tourmaline: NaMg3[Cr,Fe+3]6B3Si6O27(OH)3(OH,F)
- Dravite Tourmaline: NaMg3Al6B3Si6O27(OH)3(OH,F)
- Elbaite Tourmaline: Na(Li,Al)3Al6B3Si6O27(OH)3(OH,F)
- Feruvite Tourmaline: CaFe+23Al6B3Si6O27(OH)3(OH,F)
- Foitite Tourmaline: [][Fe+22(Al,Fe+3)]Al6B3Si6O27(OH)3(OH,F)
- Liddicoatite Tourmaline: Ca(Li,Al)3Al6B3Si6O27(OH)3(OH,F)
- Olenite Tourmaline: NaAl3Al6B3Si6O27(OH)3(OH,F)
- Povondraite Tourmaline: NaFe+33Fe+36B3Si6O27(OH)3(OH,F)
- Schorl Tourmaline: Na(Fe,Mn)3Al6B3Si6O27(OH)3(OH,F)
- Uvite Tourmaline: CaMg3(Al5Mg)B3Si6O27(OH)3(OH,F)
- Class: cyclosilicates
- Crystal system: hexagonal-rhombohedral; 3m
- Crystal habit: commonly forms prismatic crystals with well developed
trigonal prism and second-order hexagonal prism faces, can be elongated or
flattened, commonly vertically striated. In cross section the prism faces
often round into one another giving the appearance of a spherical triangle.
Doubly terminated tourmaline crystals often show different forms at each end of the
vertical axis. Also radiating, acicular, columnar, massive.
- Twinning: very rare and simple on pyramidal planes such as {1011}
- Specific gravity: 2.96 - 3.31 (buergerite 3.31, dravite 3.03-3.15, elbaite 3.03-3.10, liddicoatite 3.02-3.08, schorl 3.10-3.25 and uvite 2.96-3.06)
- Index of refraction: 1.610-1.735 (buergerite 1.655-1.735, dravite 1.610-1.661, elbaite 1.615-1.655, liddicoatite 1.621-1.637, schorl 1.625-1.675 and uvite 1.612-1.638)
- Birefringence: 0.016-0.080 (buergerite 0.080, dravite 0.021-0.026, elbaite 0.016-0.024, liddicoatite 0.016,schorl 0.025-0.035 and uvite 0.017-0.020)
- Pleochroism: strong in all species
- Hardness: 7.0 - 7.5
- Color: tourmalines occur in all colors. Buergerite is dark brown to black.
Dravite is usually
brown to black, can be colorless. Elbaite
and liddicoatite occur in a wide range of colors and shades including brown tourmaline, green tourmaline
(see our selection of natural color green tourmaline earrings with many different shades of light to dark green), blue tourmaline (see also our natural color blue tourmaline gemstones, yellow tourmaline, pink tourmaline (see our selection of natural color pink tourmaline earrings) as well as red tourmaline and even colorless tourmaline. Black tourmaline is usually the variety Schorl
although schorl can also be dark blue or dark blue-green. Uvite is usually black,
brown or green. Tourmaline crystals
are often color zoned concentrically and/or along the C axis.
- Luster: vitreous to resinous, can occur with chatoyancy due to tubular cavities parallel to the C axis.
- Transparency: transparent to opaque
- Cleavage: poor in all species except buergerite which has distinct prismatic cleavage
- Fracture: conchoidal, brittle
- Streak: white
Go up to the Tourmaline Information Index
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 (see our natural color rubellite tourmaline jewelry) for pink to red shades,
indicolite for blue tourmaline (see our natural color blue tourmaline jewelry), 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 crystals and black tourmaline crystals.
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.
Go up to the Tourmaline Information Index
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, morganite, 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
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.
Go up to the Tourmaline Information Index
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.
See Our Natural Tourmaline Necklaces
Go up to the Tourmaline Information Index
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.
Metaphysical properties for the specific colors of tourmaline are
given below:
Black Tourmaline Crystals: 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 additional metaphysical info, see our Metaphysical Books page.
Tourmaline Item Categories:
Select a link to view our on-line inventory of that category
for all tourmaline varieties
(these pages have many images and will
load more slowly).
This is the end of our Tourmaline Factsheet and Information page.
Last Updated: June 17, 2018
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