Opal (Common) Gemstone & Information | Gemopedia by JTV | Gemopedia™

Opal (Common)

While we often think of opal in terms of phenomenal play of color, this gemstone family is full of other unique and appealing members that have their own allure. Gems can be transparent, translucent or opaque and form in almost any color in many locations around the world. Get to know all the varieties of this unique family by looking at our fire opal, dendritic opal, hyalite, Caramel Spice Opal (TM), Morado Opal (TM), along with even more blue, pink and green varieties. With such an endless array, opal truly is the 'Queen of Gemstones'.

Colors

Almost Any Color

  • Opal-common classification

    CommonName
    Opal (Common)
    Species
    Opal
    Variety
    Common Opal
    Colors
    Almost Any Color
    AlternateNames
    Potch, Opal Without Play-Of-Color, Common Opal, Colored Opal
    GemstoneGroups
    KeySeparations
    Appearance, RI and fluorescence
    ClassificationComments
    Common opal shows no play-of-color and is called potch when found in association with precious opal. Agate opal or banded opal has concentric bands and has an appearance similar to agate. Andean opal is a greenish blue opal from Peru that sometimes contains dendrite inclusions. Cachalong opal, mother of pearl opal or Kalmuck agate opal is translucent to opaque milky bluish white and it has a similar appearance to porcelain or mother of pearl. This stone is often used form cameos. Cat's-eye opal is brownish yellow to yellowish brown and has needle inclusions that create chatoyancy. The stones might display what is called the "milk and honey" effect. Dendritic or moss opal has dendritic inclusions that look like moss. Girasol opal is a hyalite opal that is semitransparent to translucent. It has microscopic inclusions that give it blueish white sheen with reddish reflections and has an appearance similar to moonstone. Hyalite opal or water stone is colorless to translucent white with strong sheen. Honey opal is orange brown in color. Iron opal is yellow or red common opal.Jasper opal is brecciated Jasper cemented by opal. Milk opal is white common opal.Onyx opal is banded opal. Prase opal or chrysopal is a translucent to opaque green common opal. The yellowish green material looks similar to chrysoprase. Wax opal is a yellowish in color and has a waxy luster. Wood opal or zeasite is dark brown to black opaque fossilized wood replaced by opal.
  • Opal-common chemistry & crystallography

    ChemicalName
    hydrated silicon dioxide
    ChemicalFormula
    SiO2.nH2O
    Synthesis
    CrystalSystem
    NA
    ChemistryClassification
    Silicate
    Nature
    Natural
    Crystallinity
    Amorphous
    ChemistryComments
  • Opal-common optical properties

    Transparency
    Translucent - Opaque
    Dispersion
    OpticalComments
    RefractiveIndex
    1.37-1.47
    Birefringence
    OpticCharacter
    NA
    OpticSign
    PolariscopeReaction
    Singly Refractive (SR) With ADR
    Fluorescence
    SWUV: inert to strong green or yellowish green
    LWUV: inert to strong green or yellowish green
    CCFReaction
    Pleochroism
    None
  • Opal-common characteristic physical properties

    Hardness
    5-6.5
    CharacteristicComments
    Streak
    White
    SpecificGravity
    1.98-2.5 Typical:2.15
    Toughness
    Varies
    Inclusions
    Luster
    Vitreous
    Stability
    Poor
    Fracture
    Conchoidal, Uneven
    Cleavage
    None