Boulder Opal Gemstone & Information | Gemopedia by JTV | Gemopedia™
Known for its lively, flaming color displays, boulder opal is in high demand by collectors and jewelry designers. As opposed to cut opal gems, boulder opal features small opal veins running through its matrix. The precious opal's rainbow of colors make a dramatic contrast to the rich earthy reds and browns of the host rock, creating a one-of-a-kind display.
Brown With Seams Of Play-Of-Color
Boulder-opal classificationCommonNameBoulder OpalSpeciesOpalVarietyBoulder OpalColorsBrown With Seams Of Play-Of-ColorAlternateNamesPrecious Opal, Natural Opal Type 2, Yowah OpalGemstoneGroupsKeySeparationsAppearance, RI and fluorescenceClassificationCommentsYowah opal is a boulder matrix opal that is cut to display the small seams mixed through out the ironstone.
Boulder-opal chemistry & crystallographyChemicalNamehydrated silicon dioxideChemicalFormulaSiO2-nH2OSynthesisCrystalSystemNAChemistryClassificationSilicateNatureNaturalCrystallinityAmorphousChemistryComments
Boulder-opal optical propertiesTransparencyTransparent - OpaqueDispersionStrength: noneOpticalCommentsRefractiveIndex1.45
Tolerance:(+0.020/-0.080)BirefringenceOpticCharacterNAOpticSignPolariscopeReactionSingly Refractive (SR) With ADRFluorescenceSWUV: Variable
Boulder-opal characteristic physical propertiesHardness5-6.5CharacteristicCommentsStreakSpecificGravity1.98-2.25ToughnessVariesInclusionsBoulder opal will have seams of precious opal in brown ironstone, quartzite, rhyolite or basalt host rock.LusterVitreousStabilityFractureConchoidal, UnevenCleavageNone