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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
Brazilian Paraiba tourmaline
Photo courtesy of Lembeck Gems

Mozambique "Paraiba-type" tourmaline 3.71 ct
Photo courtesy of Precision Gem

Nigerian "Paraiba-type" tourmaline, 1.53 ct
Photo by Jeff Scovil
Courtesy of R.W. Wise Goldsmiths

Mozambique "Paraiba-type" tourmaline,
8.14 ct, unheated. Photo by Jeff Scovil. Courtesy of R.W. Wise Goldsmiths