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Tourmaline


Mineral Properties and Uses



Physical Properties of Tourmaline

Chemical Classification silicate
Color bluish black, black, yellow, pink, blue, green, colorless, red
Streak colorless, gray
Luster vitreous
Diaphaneity transparent to nearly opaque
Cleavage poor
Mohs Hardness 7 to 7.5
Specific Gravity 3 to 3.3
Diagnostic Properties lack of cleavage, color
Chemical Composition (Ca,K,Na,[])(Al,Fe,Li,Mg,Mn)3(Al,Cr, Fe,V)6
(BO3)3(Si,Al,B)6O18(OH,F)4
Crystal System hexagonal
Uses gemstone


Tourmaline beads
The variety in tourmaliine color is shown with this strand of beads.


Tourmaline cabs
Numerous cabochons of tourmaline from Africa. Each gem is approximately 6 millimeters by 4 millimeters.


Tourmaline gemstone
A cut piece of tourmaline. The gemstone is approximately 1.8 carats, and 9 millimeters by 7 millimeters.


Tourmaline teardrop cab
A teardrop cabochon of tourmaline from San Diego, California. The gemstone is approximately 1.4 carats, and 9 millimeters by 5 millimeters.



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Tourmaline crystals
Colorful gem-quality tourmaline crystals from Brazil showing the typical prismatic habit with striations. Image © iStockphoto and MarcelC.




Tourmaline in granite
Tourmaline in granite from Stoneham, Maine. Specimen is approximately 5 inches (12.7 centimeters) across.


Tourmaline
A close-up of tourmaline from Pierrepont, New York. The overall specimen is approximately 4 inches (10 centimeters) across.


Tourmaline from NY
Tourmaline from Pierrepont, New York. Specimen is approximately 3 inches (7.6 centimeters) across.


Tourmaline in microcline
Tourmaline in microcline from Bathurst, Ontario, Canada. Specimen is approximately 3 inches (7.6 centimeters) across.


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