Adularia (Moonstone)
Image: <a href="//commons.wikimedia.org/wiki/User:Archaeodontosaurus" title="User:Archaeodontosaurus">Didier Descouens</a> (CC BY-SA 3.0)
Mineral NameAdularia (Moonstone)
Chemical FormulaKAlSi3O8
Mohs Hardness6
Crystal Systemmonoclinic
Streak Colorwhite
CleavagePerfect in two directions, nearly at 90 degrees ({001} and {010})
Fractureuneven to conchoidal
Specific Gravity2.58
Colorscolorless, white, gray, blue (adularescence)
Transparencytranslucent to transparent
Type LocalityAdula Mts, Ticino (Tessin), Switzerland
Mineral GroupSilicates (Tectosilicates, Feldspar Group)
Usesjewelry, collector
Associated Mineralsquartz, chlorite, epidote
Rarityuncommon
Description
A large, blocky crystal of adularia, a variety of orthoclase, displaying a distinct bluish adularescence across its translucent to transparent faces. The specimen is predominantly colorless to white, with some darker mineral inclusions on its surface.
Geological Context
Adularia typically forms in low-temperature hydrothermal veins and alpine clefts within metamorphic rocks, often associated with regional metamorphism and tectonic activity.
