From The Gemology Project
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Chemical composition Silicon dioxide SiO2
Crystal system Trigonal
Habit Prismatic
Cleavage Poor
Fracture Conchoidal
Hardness 7
Optic nature Uniaxial +
Refractive index 1.544 - 1.553
Birefringence 0.009
Dispersion Low, 0.013
Specific gravity 2.63 - 2.65
Lustre Vitreous
Pleochroism Weak to strong
Faceted Amethyst
Photo courtesy of
Precision Gems

Amethyst image gallery

Amethyst is a purple variety of the mineral quartz. It occurs in all intensities of the color purple from a light pastel to a depth of royal splendor. Until the beginning of the 20th century it was quite rare and costly. When vast deposits were found in Brazil, amethyst became very accessible and affordable. Amethyst has always been linked to the thinking process, ensuring clarity of vision. It inspires creativity, courage and valor. Amethyst has been successfully synthesized in the lab, so buyers need to be sure their source is qualified to separate natural from lab grown material.


Amethyst is a type I stone in the GIA clarity grading system is usually free from eye visible inclusions. Typical inclusions visible with magnification are:

  • liquid feathers "fingerprints"
  • 2-phase, 3-phase inclusions
  • negative crystals
classic "fingerprint" inclusion
30X Magnification
By Barbra Voltaire