Hackmanite Gemstone & Information | Gemopedia by JTV | Gemopedia™
Discovered in Greenland in the late 1890's, hackmanite is named for Finnish geologist Victor Hackman. It is a rare occurrence to find gem-grade hackmanite; at best, most crystals are translucent. Hackmanite is the light pink to pale violet variety of sodalite. It is a particularly unusual gem because it exhibits a special optical property known as "tenebrescence," a type of reversible photochromism. This feature allows the gems to temporarily change color when exposed to different light forms. While hackmanite gems are usually pink to violet, the color quickly fades to gray or greenish-white in sunlight, and will slowly return to the original color after changing the light. Its tenebrescent property makes hackmanite a prized mineral for collectors.
Pink, Pale To Deep Violet Some White In Sunlight Others The Reverse
Hackmanite classificationCommonNameHackmaniteSpeciesSodaliteVarietyHackmaniteColorsPink, Pale To Deep Violet Some White In Sunlight Others The ReverseAlternateNamesGemstoneGroupsSodaliteKeySeparationsRI, SG, appearance and possibly fluorescenceClassificationCommentsMost hackmanite will fade in sunlight while some Afghanistan and Burma material are creamy white and turn violet or pink-red while exposed to sunlight.
Hackmanite chemistry & crystallographyChemicalNamechloric sodium aluminum silicateChemicalFormulaNa8Al6Si6O24Cl2SynthesisCrystalSystemCubicChemistryClassificationSilicateNatureNaturalCrystallinityCrystalline to AggregateChemistryComments
Hackmanite optical propertiesTransparencyTransparent - TranslucentDispersionStrength: moderate fire Value: 0.018OpticalCommentsRefractiveIndex1.483
Tolerance:(+0.004/-0.004)BirefringenceOpticCharacterNAOpticSignNAPolariscopeReactionSingly Refractive (SR)FluorescenceSWUV: Variable
LWUV: moderate to strong orange to yellowish orangeCCFReactionPleochroismNone
Hackmanite characteristic physical propertiesHardness5-6CharacteristicCommentsStreakWhiteSpecificGravity2.15-2.4 Typical:2.25ToughnessPoorInclusionsHackmanite can contain small black inclusions.LusterVitreousStabilityFractureUnevenCleavagePoor, in one direction