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").

Chemistry: SiO2;

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+].

Identification properties

Physical properties
Mohs hardness: 7
Density: 2.66±0.01 g/cm3
Cleavage: none
Fracture: conchoidal
Optical properties
Optical character: anisotropic, uniaxial, positive
Refractive Index: no =1.544, ne =1.553
Birefringence: 0.009
Pleochroism: From poor to distinct, purple-reddish-violet hues
Dispertion: 0.013 (BG);
Luster: vitreous

Inclusions and structural inhomogeneities