Ammonite Shell Gemstone & Information | Gemopedia by JTV | Gemopedia™
Ammonites were marine animals that existed during the Jurassic and Cretaceous periods, and are related to modern-day octopi, squid and cuttlefish. The same event that wiped out dinosaurs was the end of this species, as well. On rare occasions, the ammonite fossilized shells became mineralized, exhibiting a striking iridescent play of color. Ammonite is typically found as fossil specimens or as iridescent gems cut from the fossils under the trade name Ammolite.
Gray To Brown Sometimes With Iridescent Colors
Ammonite-shell classificationCommonNameAmmonite ShellSpeciesNAVarietyColorsGray To Brown Sometimes With Iridescent ColorsAlternateNamesAmmolite, Ammonite, Korite, Aapaok And CalcentineGemstoneGroupsKeySeparationsAppearance, RIClassificationCommentsFossilized shell of nautilus like creature.
Ammonite-shell chemistry & crystallographyChemicalNamePrimarily aragonite or calcite; may also contain pyrite, silica and other materialsChemicalFormulafossilized ammonite shellSynthesisCrystalSystemNAChemistryClassificationOrganicNatureNaturalCrystallinityChemistryComments
Ammonite-shell optical propertiesTransparencyOpaqueDispersionOpticalCommentsRefractiveIndex1.52-1.68
Tolerance:variesBirefringence0.155OpticCharacterNAOpticSignNAPolariscopeReactionAggregate (AGG)FluorescenceSWUV: Inert
Ammonite-shell characteristic physical propertiesHardness4CharacteristicCommentsStreakSpecificGravity2.75-2.8 Typical:2.7ToughnessVariesInclusionsWell preserved specimens show nautilus or spiral like appearance. Rare specimens display iridescence with mosaic patterns. Due the nature of the material it is often stabilized with polymers.LusterVitreousStabilityPoorFractureGranular, UnevenCleavageNone