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Geosciences LibreTexts

16.05.04: Prasiolite

  • Page ID
    4089
  • Prasiolite
    Chemical composition SiO2 Silicon dioxide
    Crystal system Trigonal
    Habit Prismatic
    Cleavage Poor
    Fracture Conchoidal
    Hardness 7
    Optic nature Uniaxial +
    Refractive index 1.544 - 1.553
    Birefringence 0.009
    Dispersion 0.013
    Specific gravity 2.63 - 2.65
    Lustre Vitreous
    Pleochoism Weak to strong

    File:Green quartz.jpg

    Figure \(\PageIndex{1}\): Brazil

    Prasiolite is the green variety of quartz.
    The color is caused by the heating of either natural occurring amethyst (by exposure to sunlight or artificial) or by artificial heat treatment of irradiated amethyst. The former will give a more stable green color that is less prone to fading.

    Synonyms: Prasiolita, greened amethyst, green quartz.
    Misnomers: Green amethyst.

    The name "prasiolite" should not be confused with prasolite (a green variety of the chlorite group) and praseolite which is the green variety of cordierite.

    Diagnostics

    Chelsea Colour Filter

    Reactions under incandescent light:

    Irradiated green quartz: red.
    Heat treated green quartz: green.