Sunstone (Oligoclase) Gemstone & Information | Gemopedia by JTV | Gemopedia™

Sunstone (Oligoclase)

A gem known since ancient times, sunstone is a type of feldspar formed and crystallized in lava flows. Radiating with the power of eternal light, sunstone has been reportedly found in the tombs of Viking sailors who believed it would aid in their journey through both life and the afterlife. A distinguishing feature of sunstone is its metallic schiller, which rolls across the stone's surface. The effect is due to the presence of small plate-like inclusions of minerals such as hematite or native copper. These inclusions interfere with the passage of light, causing it to scatter. If the inclusions are larger and visible to the eye, they create glittery star-like reflections that gemologists refer to as aventurescence.

Colors

Yellow, Orange, Brown

  • Sunstone-oligoclase classification

    CommonName
    Sunstone (Oligoclase)
    Species
    Oligoclase
    Variety
    Sunstone
    Colors
    Yellow, Orange, Brown
    AlternateNames
    GemstoneGroups
    Feldspar
    KeySeparations
    Appearance, RI, birefringence, optic character and magnification. Adularescence in a stone indicates orthoclase.
    ClassificationComments
  • Sunstone-oligoclase chemistry & crystallography

    ChemicalName
    calcium aluminum silicate
    ChemicalFormula
    KAlSiO8
    Synthesis
    CrystalSystem
    Triclinic
    ChemistryClassification
    Silicate
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Sunstone-oligoclase optical properties

    Transparency
    Semitransparent - Opaque
    Dispersion
    OpticalComments
    RefractiveIndex
    1.539-1.547
    Birefringence
    0.007-0.01
    OpticCharacter
    Biaxial
    OpticSign
    Negative
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Inert
    LWUV: Inert
    CCFReaction
    Pleochroism
    Unobservable
  • Sunstone-oligoclase characteristic physical properties

    Hardness
    6
    CharacteristicComments
    Streak
    SpecificGravity
    2.62-2.67 Range:0.02/-0.03 Typical:2.65
    Toughness
    Poor
    Inclusions
    Sunstones contain tiny reddish to golden or green platelets of hematite or goethite. Stones might show a four-rayed star with slivery adularescence if fine needles intersect.
    Luster
    Vitreous
    Stability
    Good
    Fracture
    Uneven, Splintery
    Cleavage
    Perfect, in two directions