Coral (Calcareous) Gemstone & Information | Gemopedia by JTV | Gemopedia™
Coral has been prized throughout history for its natural beauty. Like pearl, coral is also an organic gem consisting of more than 90% calcium carbonate. All coral consists of the remains of skeleton-like support structures that were built by colonies of very small marine animals, known as coral polyps. Proteinaceous coral differs from calcareous coral because it is made up of strong keratin proteins.
Light Pink, Dark Red, Orange, White, Cream, Blue, Purple
Coral-calcareous classificationCommonNameCoral (Calcareous)SpeciesNAVarietyColorsLight Pink, Dark Red, Orange, White, Cream, Blue, PurpleAlternateNamesGemstoneGroupsKeySeparationsRI, birefringence blink, magnification and fluorescenceClassificationCommentsMisnomer: polypite
Coral-calcareous chemistry & crystallographyChemicalNamecalcium carbonateChemicalFormulaCaCO3SynthesisCrystalSystemNAChemistryClassificationOrganicNatureNaturalCrystallinityNon-CrystallineChemistryComments
Coral-calcareous optical propertiesTransparencySemitranslucent - OpaqueDispersionOpticalCommentsRefractiveIndex1.486-1.658Birefringence0.172-0.172OpticCharacterOpticSignPolariscopeReactionAggregate (AGG)FluorescenceSWUV: White:inert to weak to strong bluish whiteLight and dark orange, red and pink: inert to orange to pinkish orangeDark red: inert to dull red to purplish red
LWUV: White:inert to weak to strong bluish whiteLight and dark orange, red and pink: inert to orange to pinkish orangeDark red: inert to dull red to purplish redCCFReactionPleochroismNone
Coral-calcareous characteristic physical propertiesHardness3.5-4CharacteristicCommentsStreakSpecificGravity2.6-2.7 Typical:2.65ToughnessFairInclusionsCalcareous coral has a wavy fibrous structure with polyp cavities in cross section the branches have concentric web like structure.LusterVitreousStabilityPoorFractureUneven, SplinteryCleavageNone