Amethyst

Absorption Spectrum
Weak band, 550-520

Birefringence
0.009

Birthstone
February

Cleavage
None or indistinct

Colors
Pale lilac to deep reddish purple. May have color zoning.

Crystallography
Hexagonal (trigonal)

Dispersion
0.013

Enhancements
Amethyst can be heat treated to improve the color or change it to citrine. Not common.

Etymology
From the Ancient Greek amethystos, meaning “not drunk.” It was believed you could drink all night and remain sober if you had an amethyst in your mouth.

Formula
SiO2

Fracture
Conchoidal to uneven

Fracture Luster
Vitreous

Hardness
7

Inclusions
Prismatic crystals and negative cavities, thumbprint marks, so-called rippled fractures, and twinning lines.

Luminescence
Inert to weak blue in SW. Inert in LW.

Luminescence Present
Yes

Luminescence Type
Fluorescent, UV-Short

Luster
Vitreous

Occurrence
Generally in pegmatites and veins. Found in geodes in alluvial deposits.

Optic Sign
Uniaxial +

Optics
o = 1.544; e = 1.553 (very constant). Uniaxial (+)

Pleochroism
Weak to moderate, purple and reddish purple.

Polish Luster
Vitreous

Refractive Index
1.544–1.553

Specific Gravity
2.651

Transparency
Transparent to translucent

Typical Treatments
Heat Treatment

Variety of
Quartz

Wearability
Very Good