Amethyst Gemstone & Information | Gemopedia by JTV | Gemopedia™
Whether in faceted stones, crystal specimens, polished pebbles or beads, amethyst has enjoyed popularity in nearly every culture throughout its ancient history. Before the lucrative deposits of Africa and South America were discovered, amethyst was as treasured as ruby and emerald. February's traditional birthstone, striking purple amethyst is the most popular gemstone of the quartz group.
Purple Through Violetish Purple
Amethyst classificationCommonNameAmethystSpeciesQuartzVarietyAmethystColorsPurple Through Violetish PurpleAlternateNamesSpirit Quartz If It Has Secondary Pale Amethyst Growth Coverage, Rose Of France If Pale LilacGemstoneGroupsKeySeparationsRefractive index, birefringence, optic character and optic figure. A bull's-eye optic figure is determinative for quartz. Might also show Airy's spiral. The presence of Brazil-law twinning is a means of separating amethyst from scapolite.ClassificationCommentsAmethyst is commonly found in geodes. Stones might be piezoelectric: able to generate electricity produced by mechanical pressure, Pyroelectricity: development of opposite charges at the ends of the axis due to change in temperature and triboluminescent: luminescence produced by friction.
Amethyst chemistry & crystallographyChemicalNamesilicon dioxide (aka silica)ChemicalFormulaSiO2SynthesisCrystalSystemTrigonalChemistryClassificationSilicateNatureNaturalCrystallinityCrystallineChemistryComments
Amethyst optical propertiesTransparencyTransparent - TranslucentDispersionStrength: weak fire Value: 0.013OpticalCommentsRefractiveIndex1.544-1.553
Tolerance:very constantBirefringence0.009-0.009OpticCharacterUniaxialOpticSignPositivePolariscopeReactionDoubly Refractive (DR)FluorescenceSWUV: Inert to weak blue
LWUV: InertCCFReactionPleochroismDichroic, weak to moderate purple and reddish purple
Amethyst characteristic physical propertiesHardness7CharacteristicCommentsStreakWhiteSpecificGravity2.64-2.69 Range:0.03/-0.02 Typical:2.66ToughnessGoodInclusionsAmethyst is a type II clarity stone. Color zoning in stones is often present in the form of "soap scum", "tiger stripes" or "zebra stripes", crystals, negative crystals, liquid inclusions, two-phase inclusions, partially-healed fractures, hematite needles.LusterVitreousStabilityGoodFractureConchoidalCleavageNone