16.14.05: Paraiba
- Page ID
- 4346
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Paraiba Tourmaline | |
---|---|
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 |
Figure \(\PageIndex{1}\): Brazilian Paraiba tourmaline
Photo courtesy of Lembeck Gems
Paraiba type
Figure \(\PageIndex{2}\): Mozambique "Paraiba-type" tourmaline 3.71 ct Photo courtesy of Precision Gem |
Figure \(\PageIndex{3}\): Nigerian "Paraiba-type" tourmaline, 1.53 ct Photo by Jeff Scovil Courtesy of R.W. Wise Goldsmiths |
Figure \(\PageIndex{4}\): Mozambique "Paraiba-type" tourmaline, 8.14 ct, unheated. Photo by Jeff Scovil. Courtesy of R.W. Wise Goldsmiths |