Hackmanite Gemstone & Information | Gemopedia by JTV | Gemopedia™

Hackmanite

Discovered in Greenland in the late 1890's, hackmanite is named for Finnish geologist Victor Hackman. It is a rare occurrence to find gem-grade hackmanite; at best, most crystals are translucent. Hackmanite is the light pink to pale violet variety of sodalite. It is a particularly unusual gem because it exhibits a special optical property known as "tenebrescence," a type of reversible photochromism. This feature allows the gems to temporarily change color when exposed to different light forms. While hackmanite gems are usually pink to violet, the color quickly fades to gray or greenish-white in sunlight, and will slowly return to the original color after changing the light. Its tenebrescent property makes hackmanite a prized mineral for collectors.

Colors

Pink, Pale To Deep Violet Some White In Sunlight Others The Reverse

  • Hackmanite classification

    CommonName
    Hackmanite
    Species
    Sodalite
    Variety
    Hackmanite
    Colors
    Pink, Pale To Deep Violet Some White In Sunlight Others The Reverse
    AlternateNames
    GemstoneGroups
    Sodalite
    KeySeparations
    RI, SG, appearance and possibly fluorescence
    ClassificationComments
    Most hackmanite will fade in sunlight while some Afghanistan and Burma material are creamy white and turn violet or pink-red while exposed to sunlight.
  • Hackmanite chemistry & crystallography

    ChemicalName
    chloric sodium aluminum silicate
    ChemicalFormula
    Na8Al6Si6O24Cl2
    Synthesis
    CrystalSystem
    Cubic
    ChemistryClassification
    Silicate
    Nature
    Natural
    Crystallinity
    Crystalline to Aggregate
    ChemistryComments
  • Hackmanite optical properties

    Transparency
    Transparent - Translucent
    Dispersion
    Strength: moderate fire Value: 0.018
    OpticalComments
    RefractiveIndex
    1.483
    Tolerance:(+0.004/-0.004)
    Birefringence
    OpticCharacter
    NA
    OpticSign
    NA
    PolariscopeReaction
    Singly Refractive (SR)
    Fluorescence
    SWUV: Variable
    LWUV: moderate to strong orange to yellowish orange
    CCFReaction
    Pleochroism
    None
  • Hackmanite characteristic physical properties

    Hardness
    5-6
    CharacteristicComments
    Streak
    White
    SpecificGravity
    2.15-2.4 Typical:2.25
    Toughness
    Poor
    Inclusions
    Hackmanite can contain small black inclusions.
    Luster
    Vitreous
    Stability
    Fracture
    Uneven
    Cleavage
    Poor, in one direction