Paraiba
From The Gemology Project
| 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 |
Paraiba type
|
|
|
|
| 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 |
