Topaz Gemstone & Information | Gemopedia by JTV | Gemopedia™

Topaz

Topaz can be both very common (when clear, or in certain colors like brown, which can turn blue when treated) and very rare (when found in natural beautiful colors rare to the species, like pink and red). Topaz's popularity stems from the gem's good wearability and affordability. Topaz is also often altered with special surface treatments to give it unusual colors and iridescent effects, like mystic, ocean, kiwi, and orchid topaz. Topaz is also a popular birthstone, as blue topaz is December's primary birthstone and yellow topaz is a birthstone for November.

Colors

Pale Pink To Strong Red, Purpleish Red, Reddish Purple, Orange Red, Orange, Yellow, Yellowish To Pinkish Yellow, Yellowish Brown, Brown, Light Blue To Dark Greenish Blue, Pale Green, Colorless, Grayish

  • Topaz classification

    CommonName
    Topaz
    Species
    Topaz
    Variety
    Colors
    Pale Pink To Strong Red, Purpleish Red, Reddish Purple, Orange Red, Orange, Yellow, Yellowish To Pinkish Yellow, Yellowish Brown, Brown, Light Blue To Dark Greenish Blue, Pale Green, Colorless, Grayish
    AlternateNames
    Sherry Topaz, Hyacinth Topaz, Imperial Topaz, Precious Topaz, Swiss Blue, London Blue, Mystic Topaz
    GemstoneGroups
    KeySeparations
    refractive index, birefringence, optic character; possibly specific gravity. The refractive index of blue topaz varieties may be lower than others by as much as 0.01. Some topaz is coated, causing an inert reaction to LWUV and SWUV, different spectra and variable reactions to a CCF test.
    ClassificationComments
    Crystal habit is typically an orthorhombic prism, with rhombic cross-section, basal cleavage and striations along the length of the crystal (c-axis). Misnomers: slave's diamond-colorless topaz, Brazilian sapphire-blue topaz. Sherry topaz: brownish yellow to orange to yellow brown the color of sherry. Hyacinth topaz: dark orange, dark orange-red to reddish brown. Imperial topaz: top color medium reddish orange. Precious topaz: yellow and orange. Sky blue topaz: light blue irradiated topaz. Swiss blue topaz: medium blue irradiated topaz. London blue topaz: darker greenish blue irradiated topaz. Colorless and gray topaz has RI 1.609 to 1.617. Red, pink, purple, orange, yellow and brown stones: RI typically 1.629 to 1.637. Surface treated green stones: RI 1.609 to 1.617. Many times the the stones are long and thin and show pleochroic colors at the far ends of the stone. Birthstone for November
  • Topaz chemistry & crystallography

    ChemicalName
    fluorosilicate of aluminum with hydroxyl
    ChemicalFormula
    Al2(F,OH)2SiO4
    Synthesis
    CrystalSystem
    Orthorhombic
    ChemistryClassification
    Silicate
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Topaz optical properties

    Transparency
    Transparent
    Dispersion
    Strength: weak fire Value: 0.014
    OpticalComments
    RefractiveIndex
    1.619-1.627
    Tolerance:(+0.010/-0.010)
    Birefringence
    0.008-0.01
    OpticCharacter
    Biaxial
    OpticSign
    Positive
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Variable
    LWUV: Variable
    CCFReaction
    Surface treated green: pink to red
    Pleochroism
    Dichroic, weak to moderate, varying shades of body color
  • Topaz characteristic physical properties

    Hardness
    8
    CharacteristicComments
    Streak
    White
    SpecificGravity
    3.49-3.57 Range:+/-0.04 Typical:3.53
    Toughness
    Fair
    Inclusions
    Blue stones have Type I clarity for blue and all other colors are type II clarity. Stones sometimes contain long tube-like cavities containing liquid, healed fractures and areas that look like they are starting to cleave. Stones might include 2-phase and 3-phase inclusions some of which contain more than one liquid that have not been mixed. Stones have a coating on the pavilion or crown of stone There might scratches of treated surface of the stone that show colorless areas underneath. Surface treated green topaz is blue green in appearance and looks spotty there might also be blue color concentrations in surface reaching fractures.
    Luster
    Vitreous
    Stability
    Good
    Fracture
    Conchoidal
    Cleavage
    Perfect, in one direction