Almandite Garnet Gemstone & Information | Gemopedia by JTV | Gemopedia™
Though they all have the same crystal structure (cubic, like diamond and spinel), garnet is an entire group of minerals that vary in their chemical composition, resulting in a variety of gems featuring different colors and properties. Though some varieties of red garnet are common and found on nearly every continent on Earth, other garnets like orange spessartite, green demantoid and tsavorite, are much less abundant. There are more than 20 garnet species, but the five most important include pyrope and almandite (the combination of which creates rhodolite), spessartite, grossularite or grossularite (which includes hessonite and tsavorite), and andradite (which includes demantoid). Garnets of all species are the birthstone for January, so January babies aren't limited to the well-known red varieties.
Brownish Orange To Brownish Red To Purplish Red
Almandite-garnet classificationCommonNameAlmandite GarnetSpeciesAlmandite GarnetVarietyColorsBrownish Orange To Brownish Red To Purplish RedAlternateNamesAlmandine GarnetGemstoneGroupsGarnetKeySeparationsrefractive index, SR nature and spectrum. 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.ClassificationCommentsMisnomers: Colorado ruby or Cape ruby.Some large stones are cut shallow because the dark saturation and concave back cabochons can also be found.
Almandite-garnet chemistry & crystallographyChemicalNameiron aluminum silicateChemicalFormulaFe3Al2(SO4)3SynthesisCrystalSystemCubicChemistryClassificationSilicateNatureNaturalCrystallinityCrystallineChemistryComments
Almandite-garnet optical propertiesTransparencyTransparent - SemitranslucentDispersionStrength: moderate fire Value: 0.024OpticalCommentsRefractiveIndexOver The Limit 1.78-1.82
Tolerance:(+0.030/-0.030)BirefringenceOpticCharacterNAOpticSignNAPolariscopeReactionSingly Refractive (SR) With ADRFluorescenceSWUV: Inert
Almandite-garnet characteristic physical propertiesHardness7-7.5CharacteristicCommentsStreakSpecificGravity3.93-4.3 Range:0.25/-0.12 Typical:4.05ToughnessGoodInclusionsAlmandite garnet is a type II clarity stone. 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.LusterVitreousStabilityGoodFractureConchoidalCleavageNone