Glittering Stones >> Semi Precious Stones >> Tourmaline

Semi Precious Stone Tourmaline

The mineral tourmaline is a complex silicate of aluminium and boron, but because of isomorphous replacements it varies widely in composition with iron, magnesium and lithium also entering into the combination to a greater or lesser extent. Tourmaline belongs to the hexagonal system, with long, slender, prismatic acicular crystals that are usually terminated with three faces of a rhombohedron. The smaller crystals are often found in a radial pattern, and collumnar masses are common. The prisms are usually three, six, or nine sided with heavy vertical striations producing a rounded effect. Tourmaline is essentially without cleavage, its fracture is conchoidal to even, its hardness is 7-7.5, its specific gravity is 2.9-3.2, and it has a vitreous lustre inclining to resinous.


Tourmaline

Historical Facts of Tourmaline

Refractive index 1.635 – 1.675, 1.610 – 1.650
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
Hardness 7 – 7.5
Crystal Group Hexagonal
Luster Vitreous, sometimes resinous
Specific gravity 3.06 (+.20 -.06)
Density 2.82–3.32
Color Blue, green, red, yellow, pink, brown, orangy red, purplish red, black, colorless
Recognized minerals Buergerite, Chromdravite, Dravite, Elbaite, Feruvite, Foitite, Liddicoatite, Magnesiofoitite, Olenite, Povondraite, Rossmanite, Schorl, Uvite, Vanadiumdravite
Tourmaline species Dravite species, Schorl Species, Elbaite Species
Tourmaline varieties Dravite, Brazilian sapphire, schorl, rubellite variety, indicolite, verdelite or Brazilian emerald, achroite
Occurrence Brazil, Africa, Sri Lanka, Tanzania, Nigeria, Kenya, Madagascar, Mozambique, Namibia, Afghanistan, Pakistan, Malawi
Pleochroism Red Tourmaline - Definite; dark red, light red
Green Tourmaline - Strong; dark green, yellow-green
Brown Tourmaline - Definite; dark brown, light brown
Blue Tourmaline - Strong; dark blue, light blue

Gem stones Tourmaline

Tourmaline Bracelet
Tourmaline Bracelet
Tourmaline Earring
Tourmaline Earring
Tourmaline Necklace
Tourmaline Necklace
Tourmaline Rings
Tourmaline Ring

 

   
 
 
 
 
 
 
 
 

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