Gemstone library
PARAIBA TOURMALINE
Paraíba tourmalines are blue to green tourmalines coloured by copper (and manganese in the case of purple tourmalines). They were discovered in the early 1990s in Brazil. Other deposits were then discovered in Mozambique and Nigeria. These tourmalines were formed in pegmatites.
Tourmalines submitted to the LFG undergo identification in order to determine their species and any possible treatment (whereby irradiation or heating treatments are not identifiable on certain tourmalines).
CHARACTERISTICS
- Name: Paraiba Tourmaline
- Mineralogical nature: Tourmaline
- Colour: Blue, green
- Crystal system: Rhombohedral
- Chemical composition: (Na, Ca, □)(Li, Mg, Al, Fe)2(Al, Fe, Cr, V)6(BO3)3[Si6O18](O, OH, F)4
- Causes of colour: Cu2+
- Density: 3.06 to 3.12
- Hardness: 7 to 7.5
- Cleavage: None
- Fractures: Conchoidal or irregular
- Optic number: Negative uniaxial
- Refractive index: no: 1.634 to 1.650 / not: 1.610 to 1.625
- Birefringence: 0.015 to 0.028
- Dispersion: 0.017
- Pleochroism: Very clean for coloured tourmalines
- UVL: Inert
- UVC: Inert
- Treatments: Thermal treatment
- Syntheses: None
- Geographical origin: Brazil, Mozambique, Nigeria
CONTACT US :
contact@lfg.paris
(+33) 01 40 26 25 45
30, rue de la Victoire - 75009 Paris
Monday - Thusday : 9H30 to 17H00
Friday : 9h30 to 16h30
Withdrawal files at same days and time
