Fire Opal Gemstone & Information | Gemopedia by JTV | Gemopedia™
Unique and mysterious, fire opals are appropriately named for their fiery cherries, sunburst yellows and deep tangerines. Unlike many other opals, fire opal may not display play of color, and specimens that do are highly valuable. Mexico is one of today's primary fire opal sources, where this fiery gem has been treasured since the time of the Aztecs, who called it "gem of the bird of paradise" in their native language.
Yellow, Red, Orangy Red, Orange, Brown
Fire-opal classificationCommonNameFire OpalSpeciesOpalVarietyFire OpalColorsYellow, Red, Orangy Red, Orange, BrownAlternateNamesPrecious Opal, Mexican Fire Opal, Brazilian Fire Opal, Cherry Opal, Gold Opal, Sun OpalGemstoneGroupsKeySeparationsAppearance, RI and fluorescenceClassificationCommentsFire opals RI is typically between 1.420 to 1.430, but some have been found to be as low as 1.370. Some stones might show play-of-color.
Fire-opal chemistry & crystallographyChemicalNamehydrated silicon dioxideChemicalFormulaSiO2.nH2OSynthesisCrystalSystemNAChemistryClassificationSilicateNatureNaturalCrystallinityAmorphousChemistryComments
Fire-opal optical propertiesTransparencyTransparent - OpaqueDispersionOpticalCommentsRefractiveIndex1.45
Tolerance:(+0.020/-0.080)BirefringenceOpticCharacterNAOpticSignPolariscopeReactionSingly Refractive (SR) With ADRFluorescenceSWUV: Inert to moderate greenish brown
LWUV: Inert to moderate greenish brownCCFReactionPleochroismNone
Fire-opal characteristic physical propertiesHardness5-6.5CharacteristicCommentsStreakWhiteSpecificGravity1.97-2.23 Typical:2.15ToughnessVariesInclusionsFire opal might have a cloudy appearance, show color zoning and have mineral or fluid inclusions.LusterVitreousStabilityPoorFractureConchoidal, UnevenCleavageNone