Chiastolite Gemstone & Information | Gemopedia by JTV | Gemopedia™

Chiastolite

Chiastolite is an opaque variety of andalusite that exhibits a unique cross-like pattern, an internal characteristic caused by carbonaceous inclusions. Sometimes called the "cross stone," this formation is seen in cross-sections of the crystal. Slices are often polished as amulets or for collecting, with no two exactly alike.

Colors

White, Gray, Reddish, Light Brown With Black Cross-Like Pattern

  • Chiastolite classification

    CommonName
    Chiastolite
    Species
    Andalusite
    Variety
    Chiastolite
    Colors
    White, Gray, Reddish, Light Brown With Black Cross-Like Pattern
    AlternateNames
    Macle Or Cross Stone
    GemstoneGroups
    KeySeparations
    Appearance, RI and SG
    ClassificationComments
    Often cut as a tablet to display cross pattern.
  • Chiastolite chemistry & crystallography

    ChemicalName
    aluminum silicate + carbon
    ChemicalFormula
    Al2SiO5 + C
    Synthesis
    CrystalSystem
    Orthorhombic
    ChemistryClassification
    Silicate
    Nature
    Natural
    Crystallinity
    Aggregate
    ChemistryComments
  • Chiastolite optical properties

    Transparency
    Translucent - Opaque
    Dispersion
    OpticalComments
    RefractiveIndex
    1.63-1.64
    Birefringence
    0.007-0.013
    OpticCharacter
    Biaxial
    OpticSign
    Negative
    PolariscopeReaction
    Aggregate (AGG)
    Fluorescence
    SWUV: Inert
    LWUV: Inert
    CCFReaction
    Pleochroism
    Unobservable
  • Chiastolite characteristic physical properties

    Hardness
    5-5.5
    CharacteristicComments
    Streak
    White
    SpecificGravity
    3.13-3.2 Typical:3.17
    Toughness
    Inclusions
    Luster
    Vitreous
    Stability
    Fracture
    Uneven
    Cleavage
    Good, in one direction, Poor, in one direction