Hydrogrossular Garnet Gemstone & Information | Gemopedia by JTV | Gemopedia™
Hydrogrossular garnet is typically translucent to opaque and is usually available as cabochons, but on rare occasion may be found as transparent, faceted gemstones. Generally seen as green to blue-green, pink, white, and gray, this gemstone may contain small dark gray to black inclusions and may look similar to jade if opaque. Hydrogrossular is a variety of grossular garnet where hydroxide partially replaces silica.
Green To Bluish Green, Pink, Brownish Pink, Rose Red, White, Gray
Hydrogrossular-garnet classificationCommonNameHydrogrossular GarnetSpeciesHydrogrossularVarietyColorsGreen To Bluish Green, Pink, Brownish Pink, Rose Red, White, GrayAlternateNamesGemstoneGroupsGarnetKeySeparationsRI, spectrum, appearance and maybe SG. If the stone is mixed with idocrase a clear identification is not possible.ClassificationCommentsMisnomers: African jade or Transvaal jade, garnet jade.
Hydrogrossular-garnet chemistry & crystallographyChemicalNamecalcium aluminum silicate with water or hydroxalChemicalFormulaCa3Al2(SiO4)3-x(OH)4x with (OH) partly replacing (SiO4)SynthesisCrystalSystemCubicChemistryClassificationSilicateNatureNaturalCrystallinityAggregateChemistryComments
Hydrogrossular-garnet optical propertiesTransparencyTranslucent - OpaqueDispersionOpticalCommentsRefractiveIndex1.72-1.72
Tolerance:(+0.010/-0.050)BirefringenceOpticCharacterNAOpticSignNAPolariscopeReactionAggregate (AGG)FluorescenceSWUV: Inert
LWUV: InertCCFReactionGreen: possibly pinkishPleochroismNone
Hydrogrossular-garnet characteristic physical propertiesHardness7CharacteristicCommentsStreakSpecificGravity3.15-3.55 Range:0.08/-0.32 Typical:3.47ToughnessGoodInclusionsMight have black magnetite inclusions that resemble pepper.LusterVitreousStabilityGoodFractureUneven, Granular, SplinteryCleavageNone