Selenite Gemstone & Information | Gemopedia by JTV | Gemopedia™
Selenite is the name for transparent, colorless to near colorless crystals of gypsum, a hydrous calcium sulfate that is found in a number of forms. The name "selenite" comes from the Greek word selene, meaning "moon", no doubt in reference to the gem's white glow. Gypsum, in all varieties, is very soft and has perfect cleavage so it should be handled with care.
Selenite classificationCommonNameSeleniteSpeciesGypsumVarietySeleniteColorsMostly WhiteAlternateNamesGemstoneGroupsKeySeparationsAppearance, RI and SG. Poor polished surface due to low mohs hardness.ClassificationCommentsTransparent colorless variety of gypsum.
Selenite chemistry & crystallographyChemicalNamehydrous calcium sulfateChemicalFormulaCaSO4-2H2OSynthesisCrystalSystemMonoclinicChemistryClassificationSulfateNatureNaturalCrystallinityCrystallineChemistryComments
Selenite optical propertiesTransparencyTranslucentDispersionOpticalCommentsRefractiveIndex1.52-1.529
Tolerance:(+0.001/-0.001)Birefringence0.009-0.01OpticCharacterBiaxialOpticSignPositivePolariscopeReactionDoubly Refractive (DR)FluorescenceSWUV: Inert to weak brownish white or greenish white
LWUV: Inert to weak brownish white or greenish whiteCCFReactionPleochroismNone
Selenite characteristic physical propertiesHardness1.5-2CharacteristicCommentsStreakWhiteSpecificGravity2.25-2.35 Typical:2.3ToughnessPoorInclusionsLusterWaxyStabilityFairFractureGranularCleavagePerfect, in one direction, Good, in two directions