Sphalerite Gemstone & Information | Gemopedia by JTV | Gemopedia™
With greater dispersion than diamond, sphalerite is an intriguing, yet challenging, gem. Known primarily to collectors due to its lack of hardness, sphalerite can try the patience of even the most highly skilled lapidaries who dare to fashion it into a finished gem. Not only is it extremely soft, it also has perfect cleavage, in six directions, making it extremely difficult to cut and polish! Add in the fact that it's a brittle gem, and you have an idea of the challenge that awaits its potential cutter. When that talented lapidary is, however, able to complete his task with a fashioned gem, the results are more than worth the lapidary's efforts!
Green, Yellow, Orange, Red, Brown, Gray To Black
Sphalerite classificationCommonNameSphaleriteSpeciesSphaleriteVarietyColorsGreen, Yellow, Orange, Red, Brown, Gray To BlackAlternateNamesCleiophane, Marmatite, Zinc BlendeGemstoneGroupsKeySeparationsSR nature, magnification, cleavage, spectrum, very strong dispersion, SG and possible fluorescence.ClassificationCommentsCleiophane can range from nearly colorless and pale yellow to light green. Marmatite is the black variety usually found in Marmato, Italy. Ruby Blende is the red variety of sphalerite. Stones are rarely chatoyant.
Sphalerite chemistry & crystallographyChemicalNamezinc iron sulfideChemicalFormula(Zn,Fe)SSynthesisCrystalSystemCubicChemistryClassificationSulfideNatureNaturalCrystallinityCrystallineChemistryComments
Sphalerite optical propertiesTransparencyTransparent - OpaqueDispersionStrength: extreme fire Value: 0.156OpticalCommentsRefractiveIndexOver the Limit 2.369-2.5BirefringenceOpticCharacterNAOpticSignNAPolariscopeReactionSingly Refractive (SR)FluorescenceSWUV: Inert to strong orange-red
LWUV: Inert to strong orange-redCCFReactionPleochroismNone
Sphalerite characteristic physical propertiesHardness3.5-4CharacteristicCommentsStreakYellowish To Light BrownSpecificGravity3.9-4.1 Typical:4.05ToughnessPoorInclusionsSphalerite is frequently color zoned and has very strong dispersion.LusterAdamantineStabilityFractureConchoidal, UnevenCleavagePerfect, in six directions