Moonstone
Orthoclase var. Moonstone (Adularia) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Monoclinic or Triclinic; usually found in massive or granular habits in raw form.
Mineral Group
Silicates (Tectosilicate); Feldspar Group
Chemical Formula
(K,Na)AlSi3O8 (Potassium Aluminum Silicate with Sodium)
Formation Process
Forms primarily in cool hydrothermal environment and pegmatites through the slow cooling of magma where orthoclase and albite separate into microscopic layers.
About This Crystal
The specimen appears as a rough, translucent to opaque white-grey stone exhibiting a pearly to vitreous luster. It shows a characteristic blue-white sheen known as adularescence across the surface.
Physical Characteristics
Color: White, grey, or silvery-blue; Streak: White; Cleavage: Two directions at nearly 90 degrees; Fracture: Uneven to conchoidal; Specific Gravity: 2.56-2.59; Fluorescence: Weak orange or blue under UV.
Optical Properties
Displays adularescence caused by light scattering between layers of orthoclase and albite. Refractive Index: 1.518-1.526; Birefringence: 0.005-0.008; Doubly refractive.
Hardness & Durability
Origin Region
Notably sourced from Sri Lanka, India, Myanmar, Madagascar, and Tanzania.
Hardness & Durability
Mohs Hardness: 6.0 to 6.5. It is somewhat brittle with perfect cleavage, making it susceptible to cracking if dropped or struck.
Care & Maintenance
Avoid ultrasonic cleaners and steam cleaners. Clean with warm soapy water and a soft brush. Store away from harder stones like diamonds or sapphires to prevent scratching.
Rarity & Value
Common to Uncommon. Value is highly dependent on the intensity and transparency of the adularescence (blue sheen). Fine blue moonstone is increasingly rare.
Special Characteristics
Features adularescence (shiller effect). Some specimens can exhibit chatoyancy (cat's eye effect) or asterism (four-pointed star) if cut correctly.
Lore & History
Historically used in Roman and Greek jewelry and associated with lunar deities. Traditionally viewed as a 'stone of new beginnings' and inner growth, often linked to the Crown and Third Eye chakras.