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Geosciences LibreTexts

16.14.05: Paraiba

  • Page ID
    4346
  • 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

    File:Paraiba1.jpg

    Figure \(\PageIndex{1}\): Brazilian Paraiba tourmaline
    Photo courtesy of Lembeck Gems

    Paraiba type

    File:Mozparaiba.jpg

    File:6403 d.jpg

    File:Purplecuprian.jpg

    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