Moonstone
Orthoclase var. Moonstone (Feldspar) · Semi-Precious Gemstone
Crystal System
Monoclinic (Orthoclase) and Triclinic (Albite) lamellae; typically found in massive or rolled forms
Mineral Group
Silicates (Tectosilicates subclass, Feldspar group)
Chemical Formula
((K,Na)AlSi3O8) with alternating layers of orthoclase and albite
Formation Process
Magmatic crystallization in pegmatites and metamorphic environments; secondary unmixing (exsolution) of two feldspars during cooling
About This Crystal
A translucent to opaque tumble-polished stone showing a pale grey-green body color with visible internal white lamellar veining and fractures. It exhibits a soft vitreous to pearly luster.
Physical Characteristics
Color: Grey-green with white streaks; Streak: White; Cleavage: Two directions at nearly 90 degrees; Fracture: Conchoidal to uneven; Specific Gravity: 2.56-2.59; Fluorescence: Weak bluish or orange under UV.
Optical Properties
Adularescence (billowy light effect caused by light scattering between layers); Refractive Index: 1.518-1.526; Birefringence: 0.005-0.008; Doubly refractive.
Hardness & Durability
Origin Region
Sri Lanka (classic adularescent), India (colorful varieties), Madagascar, and Myanmar
Hardness & Durability
Mohs Hardness: 6.0-6.5; Toughness: Poor due to perfect cleavage; brittle stability
Care & Maintenance
Avoid ultrasonic and steam cleaners; clean with warm soapy water and a soft brush. Store away from harder stones like quartz or sapphire to prevent scratching.
Rarity & Value
Common (though high-quality blue sheen is rarer); Value factors include transparency and strength of adularescence; Treatments: Generally untreated, occasionally coated.
Special Characteristics
Adularescence (schiller effect) and occasional chatoyancy; the specimen shows distinct internal layering/wispy inclusions typical of feldspar varieties.
Lore & History
Historically associated with lunar deities and protection during travel; in traditional lore, it is believed to balance emotions and represent new beginnings. Used in Roman jewelry since 100 AD.