Natural Freshwater Pearl Gemstone & Information | Gemopedia by JTV | Gemopedia™
Natural freshwater pearls occur in freshwater mollusks without the intervention of humans. These pearls are beautiful accidents of nature caused by an irritant that becomes lodged inside the mollusk. The animal naturally coats the irritant with nacre to protect its sensitive internal tissues, creating a pearl. Natural freshwater pearls are rare and are usually found by fishermen harvesting the mollusks.
White, Cream, Golden, Silver, Gray, Brown, Black
Natural-freshwater-pearl classificationCommonNameNatural Freshwater PearlSpeciesNAVarietyNatural Freshwater PearlColorsWhite, Cream, Golden, Silver, Gray, Brown, BlackAlternateNamesGemstoneGroupsKeySeparationsrefractive index, birefringence blink, specific gravity and magnification. A "tooth test" is commonly used in which a pearl is rubbed against a tooth; if gritty, this is an indication that the surface is nacre, versus plastic and glass imitations that feel smooth. X-rays are the only nondestructive test to confirm natural versus cultured origin.ClassificationComments
Natural-freshwater-pearl chemistry & crystallographyChemicalNamecalcium carbonate + conchiolin and waterChemicalFormulaCaCO3SynthesisCrystalSystemNAChemistryClassificationOrganicNatureNaturalCrystallinityAggregateChemistryComments
Natural-freshwater-pearl optical propertiesTransparencyTranslucent - OpaqueDispersionOpticalCommentsRefractiveIndex1.53-1.685Birefringence0.155OpticCharacterNAOpticSignNAPolariscopeReactionAggregate (AGG)FluorescenceSWUV: Variable
Natural-freshwater-pearl characteristic physical propertiesHardness3.5-4CharacteristicCommentsStreakSpecificGravity2.66-2.78ToughnessFairInclusionsNatural freshwater pearls will have an iridescent surface. If the pearl is drilled you can inspect the hole to look for lack of bead nucleus.LusterPearlyStabilityPoorFractureUnevenCleavageNone