Sunstone (Orthoclase) Gemstone & Information | Gemopedia by JTV | Gemopedia™

A gem known since ancient times, sunstone is a type of feldspar formed and crystallized in lava flows. Radiating with the power of eternal light, sunstone has been reportedly found in the tombs of Viking sailors who believed it would aid in their journey through both life and the afterlife. A distinguishing feature of sunstone is its metallic schiller, which rolls across the stone's surface. The effect is due to the presence of small plate-like inclusions of minerals such as hematite or native copper. These inclusions interfere with the passage of light, causing it to scatter. If the inclusions are larger and visible to the eye, they create glittery star-like reflections that gemologists refer to as aventurescence.
Colors
Yellow, Orange, Brown
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Sunstone-orthoclase classification
CommonNameSunstone (Orthoclase)SpeciesOrthoclaseVarietySunstoneColorsYellow, Orange, BrownAlternateNamesStar SunstoneGemstoneGroupsFeldsparKeySeparationsAppearance, RI, magnification. Optic character and SG helpful.ClassificationComments -
Sunstone-orthoclase chemistry & crystallography
ChemicalNamecalcium aluminum silicateChemicalFormulaKAlSiO8SynthesisCrystalSystemMonoclinicChemistryClassificationSilicateNatureNaturalCrystallinityCrystallineChemistryComments -
Sunstone-orthoclase optical properties
TransparencySemitransparent - OpaqueDispersionOpticalCommentsRefractiveIndex1.518-1.526Birefringence0.005-0.008OpticCharacterBiaxialOpticSignNegativePolariscopeReactionDoubly Refractive (DR)FluorescenceSWUV: Inert
LWUV: InertCCFReactionPleochroismUnobservable -
Sunstone-orthoclase characteristic physical properties
Hardness6CharacteristicCommentsStreakSpecificGravity2.55-2.61 Range:0.03/-0.03 Typical:2.58ToughnessPoorInclusionsSunstone will contain tiny reddish to golden or green platelets of hematite or goethite. Star sunstone will show a four-rayed star with slivery adularescence when fine needles intersect.LusterVitreousStabilityGoodFractureUneven, SplinteryCleavagePerfect, in two directions