Amethyst is a variety of crystalline quartz (α-quartz), colored in violet. The name comes from the ancient Greek "αμέθυστος" (α - "not" + μέθυστος - "to be drunk").
Crystal system: Trigonal, trigonally trapezohedral symmetry class (point symmetry group);
Color: Purple, violet, reddish violet with pale hues.
Some amethysts have alexandrite effect (transform color hue depending on the light source).
The violet color of amethyst is due to the paramagnetic complex [O- →Fe4+].
|Optical character:||anisotropic, uniaxial, positive|
|Refractive Index:||no =1.544, ne =1.553|
|Pleochroism:||From poor to distinct, purple-reddish-violet hues|
Inclusions and structural inhomogeneities
Gem basic treatments
|Heat treatment (temperature range from 100 to 200°°С)||Removing the smoky and brownish hue, as well as for clarifying dark stones|
Synthetic or Imitation gem materials
Synthetic amethyst is produced by a synthesis methods called hydrothermal growth, based on the principle of temperature gradient.
The most commonly encountered synthetic amethyst is as follows:
- clear quartz treated by irradiation;
- surface-colored quartz;
- quartz treated by "ion impregnation" - very rarely;
- doublet: quartz + glass;
- color glass.