Star Almandite Garnet Gemstone & Information | Gemopedia by JTV | Gemopedia™
Star almandite garnet exhibits the optical phenomenon called asterism, a star-like pattern created on the surface of a gemstone when light encounters parallel fibrous, or needle-like, inclusions within its crystal structure. Light that strikes the inclusions within the gem reflects off of the inclusions, creating a narrow band of light. When two or more intersecting bands appear, a star pattern is formed. Depending on the crystal, the star may have four, six, or even twelve rays. When only one band forms, it is classified as a "cat's eye".
Brownish Orange To Brownish Red, Reddish Orange To Red, Slightly Purplish Red To Reddish Purple
Star-almandite-garnet classificationCommonNameStar Almandite GarnetSpeciesAlmandite GarnetVarietyStar Almandite GarnetColorsBrownish Orange To Brownish Red, Reddish Orange To Red, Slightly Purplish Red To Reddish PurpleAlternateNamesStar GarnetGemstoneGroupsGarnetKeySeparationsAppearance, refractive index, SR nature, spectrum, SG. Color is also helpful. Stones with SG lower than 3.8 and a RI lower than 1.76 are pyrope and those with higher almandine.ClassificationComments
Star-almandite-garnet chemistry & crystallographyChemicalNameiron aluminum silicateChemicalFormulaFe3Al2(SO4)3SynthesisCrystalSystemCubicChemistryClassificationSilicateNatureNaturalCrystallinityCrystallineChemistryComments
Star-almandite-garnet optical propertiesTransparencySemitransparent - SemitranslucentDispersionStrength: weak fire Value: 0.024OpticalCommentsRefractiveIndexOver The Limit 1.78-1.82
Tolerance:(+0.030/-0.030)BirefringenceOpticCharacterNAOpticSignNAPolariscopeReactionSingly Refractive (SR) With ADRFluorescenceSWUV: Inert
Star-almandite-garnet characteristic physical propertiesHardness7-7.5CharacteristicCommentsStreakSpecificGravity3.93-4.3 Typical:4.05ToughnessGoodInclusionsAlmandite garnet is a type II clarity stone. Displays 4 or 6 rayed stars and sometimes well cut stones will show both. Stones are often found with needles that intersect at 70o to 110o angles. Zircon crystals are commonly seen with strain halos. Irregular or rounded crystals can also be found.LusterSubAdamantineStabilityGoodFractureConchoidalCleavageNone