Moonstone
Orthoclase var. Moonstone · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Monoclinic; often found as prismatic crystals, massive forms, or as rounded cabochons when processed.
Mineral Group
Silicates; Tectosilicates (Feldspar Group)
Chemical Formula
(K,Na)AlSi3O8 (Potassium Aluminum Silicate with trace Sodium)
Formation Process
Igneous/Pegmatitic: Forms through the slow cooling of magma, where orthoclase and albite separate into alternating layers (lamellae), creating its unique light-scattering property.
About This Crystal
The specimen exhibits a peach to brownish-tan body color with a vitreous to pearly luster. It appears translucent to opaque with a visible blocky, cleavage-driven structure.
Physical Characteristics
Color: Peach/Tan; Streak: White; Cleavage: Two directions at nearly 90 degrees; Fracture: Conchoidal or uneven; Specific Gravity: 2.56-2.58; Tenacity: Brittle; Fluorescence: Weak bluish or orange under UV.
Optical Properties
Refractive Index: 1.518-1.526; Birefringence: 0.005-0.008; Displays adularescence—a billowy white or blue sheen caused by light scattering between feldspar layers.
Hardness & Durability
Origin Region
Major sources include Sri Lanka, Madagascar, India, Burma (Myanmar), and Tanzania. Found in pegmatites and metamorphic rocks.
Hardness & Durability
Mohs Hardness: 6.0 to 6.5. Fair toughness, but prone to breakage along cleavage planes; moderately suitable for jewelry with protective settings.
Care & Maintenance
Avoid ultrasonic cleaners and steam cleaners. Clean with warm soapy water and a soft cloth. Store separately from harder stones like quartz or corundum to prevent scratching.
Rarity & Value
Common to Uncommon. Value is determined by the strength and color of the adularescence (blue is most valuable), clarity, and body color. Peach moonstone is generally affordable.
Special Characteristics
Adularescence (schiller effect) is the primary optical phenomenon; some specimens can also exhibit chatoyancy (cat's eye) or asterism (star effect).
Lore & History
Historically linked to lunar deities and cycles. In traditional lore, it is considered a stone of 'new beginnings' and inner growth, often associated with the Crown Chakra and Third Eye.