Zircon Gemstone & Information | Gemopedia by JTV | Gemopedia™

Zircon

Radiant zircon is the oldest known gemstone, with some crystals dating back 4 billion years, but also perhaps the most misunderstood. Unfortunately, due to the similarity of zircon's name to the lab created diamond simulant cubic zirconia, many people don't realize that zircon is a beautiful, naturally occurring stone with its own merits. Thanks to its tremendous fire and dispersion, it has been considered a less-expensive stand-in for diamond for many years, although zircon gives us many reasons to sing its praises and appreciate it in its own light.

Colors

Colorless, Very Strong Blue To Green-Blue, Yellow, Blue-Green, Yellowish Green, Yellow-Green, Brown, Orangy Yellow To Reddish Orange, Dark Brownish Red, Sometimes Purple,Gray To Bluish Gray,Brownish Gray

  • Zircon classification

    CommonName
    Zircon
    Species
    Zircon
    Variety
    Colors
    Colorless, Very Strong Blue To Green-Blue, Yellow, Blue-Green, Yellowish Green, Yellow-Green, Brown, Orangy Yellow To Reddish Orange, Dark Brownish Red, Sometimes Purple,Gray To Bluish Gray,Brownish Gray
    AlternateNames
    High Zircon, Medium Zircon, Low Zircon Or Metamict, Hyacinth, Jacinth, Jargoon Or Jargon, Beccarite, Melichrysos, Sparklite, Starlite, Stremlite
    GemstoneGroups
    KeySeparations
    Zircon exhibits strong doubling, easily observed using a 10x loupe as a doubling of back facet edges. The refractive index of zircon is over the limit of the standard gemological refractometer. Spectrum should show a distinct line at 653.5nm, but possibly up to 40 lines. Low type zircon's spectra might have fuzzy lines and not well defined. OTL RI reading, eye visable doubling and spectrum. Some low type zircon appears to be SR and amorphous.
    ClassificationComments
    Zircon affected by natural radiation may have altered crystal lattice structure that can affect some of its measurable properties. Crystals are prismatic in a tetragonal form, often with bipyramidal terminations, with square or rectangular cross-sections. Always look for doubling in 3 directions.Misnomers: Colorless zircon- Matara diamond, Blue zircon- Siam aquamarine.High and medium zircon: transparent colorless, blue, yellow to yellow-green, brownish green, orange to brown, brownish to orangy red.Low or metamict zircon: transparent brownish to yellowish green with a cloudy texture; more rarely brown to orange.Hyacinth or jacinth: yellow-red, orange, red-brown to brown.Jargoon or jargon: light yellow to colorless stones that do not show the red color of hyacinth. Traditionally they are stones from Sri Lanka.Beccarite: green zircon that displays optical properties. Melichrysos: straw yellow.Starlite or stremlite: blue heat treated zircon.Sparklite: colorless zirconHigh type RI: 1.925 to 1.984(+/-0.040); Medium type RI: 1.875 to 1.905(+/-0.030); Low type RI: 1.810 to 1.815 rarely under 1.800Low type has low birefringence and high type has high birefringence. Blue is created by heating reddish brown stones.The green metamict zircon might be slightly radioactive.
  • Zircon chemistry & crystallography

    ChemicalName
    zirconium silicate
    ChemicalFormula
    ZrSiO4
    Synthesis
    CrystalSystem
    Tetragonal
    ChemistryClassification
    Silicate
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Zircon optical properties

    Transparency
    Transparent
    Dispersion
    Strength: moderate fire Value: 0.038
    OpticalComments
    RefractiveIndex
    Over the Limit 1.81-2.024
    Birefringence
    0.002-0.059
    OpticCharacter
    Uniaxial
    OpticSign
    Positive
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Variable
    LWUV: Variable
    CCFReaction
    Blue: greenish; Green: sometimes pinkish
    Pleochroism
    Dichroic, (in blue gems) strong blue and colorless; (in red gems) moderate purplish red and reddish brown
  • Zircon characteristic physical properties

    Hardness
    6.5-7.5
    CharacteristicComments
    Streak
    White
    SpecificGravity
    3.9-4.73
    Toughness
    Varies
    Inclusions
    Blue and colorless zircons have Type I clarity. Orange, yellow, red and green zircons are Type II clarity stones. Stone might have needles and liquid inclusions. Stones might have abrasions on facet edges. Blue and white stones might show small white billowy inclusions. Low type green stones typically have a lower polish luster and often show strong parallel color zoning or repeated twinning planes, might show hazy appearance when viewed with illumination and angular "skeletal-like" tension fissures.
    Luster
    Bright Vitreous
    Stability
    Fair
    Fracture
    Conchoidal
    Cleavage
    None