Crystallography Aragonite is orthorhombic, with crystals radially oriented.Refractive Index 1.53 - 1.69Hardness 2.5 - 4.5Specific Gravity 2.6 - 2.78.Cleavage NoneHeat SensitivityYesWearability GoodEnhancements Dying, commonSpecial Care InstructionsAvoid heat and all chemicals, including perfume and other cosmetics.Birthstone JuneFormulaCaCO3 (aragonite, the outer layer) about 82 - 86%, conchiolin