Difference between revisions of "Paraiba"
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[[Image:Paraiba1.jpg|left|thumb|250px|Brazilian Paraiba tourmaline <br /> Photo courtesy of Lembeck Gems]]<br clear="left" /> | [[Image:Paraiba1.jpg|left|thumb|250px|Brazilian Paraiba tourmaline <br /> Photo courtesy of Lembeck Gems]]<br clear="left" /> | ||
− | [[Image:Mozparaiba.jpg|left|thumb|250px|Mozambique "Paraiba-type" tourmaline <br />Photo courtesy of Precision Gem]]<br clear="left" /> | + | [[Image:Mozparaiba.jpg|left|thumb|250px|Mozambique "Paraiba-type" tourmaline, 3.71 ct, heated <br />Photo courtesy of Precision Gem]]<br clear="left" /> |
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+ | [[Image:6403_d.jpg|left|thumb|250px|Nigerian "Paraiba-type" tourmaline, 1.53 ct <br />Photo by Jeff Scovil, Courtesy of R.W. Wise Goldsmiths]]<br clear="left" /> | ||
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+ | [[Image:Purplecuprian.jpg|left|thumb|250px|Mozambique "Paraiba-type" tourmaline, 8.14 ct, unheated <br />Photo by Jeff Scovil, Courtesy of R.W. Wise Goldsmiths]]<br clear="left" /> |
Revision as of 06:57, 10 April 2007
Paraiba Tourmaline | |
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Chemical composition | Complex borosilicate |
Crystal system | Trigonal |
Habit | Prismatic |
Cleavage | None |
Fracture | Conchoidal |
Hardness | 7.5 |
Optic nature | Uniaxial - |
Refractive index | 1.62 - 1.64 |
Birefringence | 0.014 - 0.022 |
Dispersion | Low, 0.018 |
Specific gravity | 3.06 |
Lustre | Vitreous |
Pleochroism | Weak to strong |