Amethyst Gemstone & Information | Gemopedia by JTV | Gemopedia™

Amethyst

Whether in faceted stones, crystal specimens, polished pebbles or beads, amethyst has enjoyed popularity in nearly every culture throughout its ancient history. Before the lucrative deposits of Africa and South America were discovered, amethyst was as treasured as ruby and emerald. February's traditional birthstone, striking purple amethyst is the most popular gemstone of the quartz group.

Colors

Purple Through Violetish Purple

  • Amethyst classification

    CommonName
    Amethyst
    Species
    Quartz
    Variety
    Amethyst
    Colors
    Purple Through Violetish Purple
    AlternateNames
    Spirit Quartz If It Has Secondary Pale Amethyst Growth Coverage, Rose Of France If Pale Lilac
    GemstoneGroups
    KeySeparations
    Refractive index, birefringence, optic character and optic figure. A bull's-eye optic figure is determinative for quartz. Might also show Airy's spiral. The presence of Brazil-law twinning is a means of separating amethyst from scapolite.
    ClassificationComments
    Amethyst is commonly found in geodes. Stones might be piezoelectric: able to generate electricity produced by mechanical pressure, Pyroelectricity: development of opposite charges at the ends of the axis due to change in temperature and triboluminescent: luminescence produced by friction.
  • Amethyst chemistry & crystallography

    ChemicalName
    silicon dioxide (aka silica)
    ChemicalFormula
    SiO2
    Synthesis
    CrystalSystem
    Trigonal
    ChemistryClassification
    Silicate
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Amethyst optical properties

    Transparency
    Transparent - Translucent
    Dispersion
    Strength: weak fire Value: 0.013
    OpticalComments
    RefractiveIndex
    1.544-1.553
    Tolerance:very constant
    Birefringence
    0.009-0.009
    OpticCharacter
    Uniaxial
    OpticSign
    Positive
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Inert to weak blue
    LWUV: Inert
    CCFReaction
    Pleochroism
    Dichroic, weak to moderate purple and reddish purple
  • Amethyst characteristic physical properties

    Hardness
    7
    CharacteristicComments
    Streak
    White
    SpecificGravity
    2.64-2.69 Range:0.03/-0.02 Typical:2.66
    Toughness
    Good
    Inclusions
    Amethyst is a type II clarity stone. Color zoning in stones is often present in the form of "soap scum", "tiger stripes" or "zebra stripes", crystals, negative crystals, liquid inclusions, two-phase inclusions, partially-healed fractures, hematite needles.
    Luster
    Vitreous
    Stability
    Good
    Fracture
    Conchoidal
    Cleavage
    None