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.

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, schorl, rubellite variety, indicolite, Brazilian sapphire, 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 Earring

Tourmaline Necklace

Tourmaline Ring