Chalcedony Gemstone & Information | Gemopedia by JTV | Gemopedia™

Chalcedony

Chalcedony is a broad gemstone family of many varieties of cryptocrystalline quartz gemstones. Chalcedony usually has a waxy luster and appears in a great variety of colors including blue, white, buff, tan, green, red, gray, black, yellow or brown. Different colored varieties of chalcedony have individual names including agate (banded), bloodstone (green with red spots), chrysoprase (apple green), carnelian (orange to red), flint (dull gray to black), jasper (spotted red, yellow, brown or green) and sard (light to dark brown).

Colors

Bluish To Whitish To Gray, Almost Any Color If Dyed

  • Chalcedony classification

    CommonName
    Chalcedony
    Species
    Quartz
    Variety
    Colors
    Bluish To Whitish To Gray, Almost Any Color If Dyed
    AlternateNames
    GemstoneGroups
    KeySeparations
    RI, SG, appearance and fracture. Color filter if dyed.
    ClassificationComments
    Misnomers: black onyx is black dyed chalcedony, green onyx is dyed green chalcedony, moonstone for milky chalcedony.
  • Chalcedony chemistry & crystallography

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

    Transparency
    Semitransparent - Opaque
    Dispersion
    Strength: none
    OpticalComments
    RefractiveIndex
    1.535-1.539
    Birefringence
    0.004-0.004
    OpticCharacter
    Uniaxial
    OpticSign
    Positive
    PolariscopeReaction
    Aggregate (AGG)
    Fluorescence
    SWUV: Inert
    LWUV: Inert
    CCFReaction
    Dyed blue: appear red or pinkish: dyed green: light grayish to reddish or pinkish
    Pleochroism
    None
  • Chalcedony characteristic physical properties

    Hardness
    6.5-7
    CharacteristicComments
    Streak
    White
    SpecificGravity
    2.55-2.7 Typical:2.6
    Toughness
    Excellent
    Inclusions
    Chalcedony is frequently dyed so look for dye concentrations. Dyed green chalcedony is evenly colored slightly blueish green and will lack dye concentrations.
    Luster
    Vitreous
    Stability
    Good
    Fracture
    Conchoidal, Granular
    Cleavage
    None