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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 |
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