Moonstone
Feldspar group, Orthoclase / Albite intergrowth var. Moonstone · Semi-Precious Gemstone
Crystal System
Monoclinic; typically forms as tabular or prismatic crystals, but commonly presented as massive, tumbled, or carved spheres.
Mineral Group
Silicates, specifically Tectosilicates (Feldspar group)
Chemical Formula
(K,Na)AlSi3O8
Formation Process
Igneous and pegmatitic formation, where alkali feldspars cool slowly, allowing microscopic intergrowths of orthoclase and albite to segregate.
About This Crystal
A polished spherical specimen exhibiting a translucent to semi-translucent body with a pale, milky-gray to brownish tone. It displays a characteristic shimmering optical phenomenon known as adularescence, highlighted by a glowing blue-to-white light flash beneath the polished surface, along with subtle internal inclusions and structural veining.
Physical Characteristics
Body color ranges from colorless to white, gray, peach, or brown; white streak; good cleavage in two directions at or near right angles; uneven to conchoidal fracture; specific gravity around 2.56-2.58; brittle tenacity; usually inert under UV light though some specimens may show faint weak pinkish or bluish fluorescence.
Optical Properties
Biaxial negative optical character; refractive index ranges from 1.518 to 1.526; exhibits strong adularescence due to light scattering from microscopic alternating lamellae of albite and orthoclase.
Hardness & Durability
Origin Region
India, Sri Lanka, Madagascar, Myanmar, Australia, and the United States. Forms primarily in igneous rocks like pegmatites and granites.
Hardness & Durability
Mohs hardness of 6 to 6.5; fair to good toughness but possesses distinct cleavage planes making it vulnerable to hard impacts; moderate wearability requiring protective settings for rings.
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid ultrasonic or steam cleaners, harsh chemicals, and sudden extreme temperature changes. Store separately in a soft pouch to prevent scratching by harder stones.
Rarity & Value
Common to Uncommon depending on body color and intensity of adularescence; high-quality specimens with vivid blue adularescence command higher prices; generally affordable as polished spheres and tumbled stones.
Special Characteristics
Displays prominent adularescence (schiller effect), creating a floating balloon-like glow of light across the surface when rotated under a light source.
Lore & History
Historically associated with lunar deities in various ancient cultures, including Roman and Hindu traditions where it was believed to be solidified moonbeams. In modern metaphysical practices, moonstone is tied to the third eye and crown chakras, symbolizing intuition, new beginnings, emotional balance, and feminine energy (though these are traditional beliefs rather than scientific claims).