Rainbow Moonstone
Feldspar group, Plagioclase series (specifically Anorthite-rich variety, commercially called Rainbow Moonstone) · Semi-Precious Gemstone and Decorative Stone
Crystal System
Triclinic, commonly forming tabular crystals or massive aggregates with distinct polysynthetic twinning.
Mineral Group
Silicates, specifically Tectosilicates (Feldspar group)
Chemical Formula
(Na,Ca)(Al,Si)4O8
Formation Process
Igneous and pegmatitic crystallization, where alkali and plagioclase feldspars exsolve into alternating microscopic lamellae as the rock cools slowly from high temperatures.
About This Crystal
The specimen is polished into a spherical shape (sphere), displaying a milky white to translucent body with striking dark tourmaline or biotite inclusions creating a contrasting dendritic pattern. It exhibits a vitreous to pearly luster and a smooth, reflective surface characteristic of expertly cut and polished feldspar minerals.
Physical Characteristics
Body color ranges from milky white to colorless with dark black inclusions; streak is white; cleavage is perfect in two directions intersecting at nearly 90 degrees; fracture is uneven to conchoidal; specific gravity is approximately 2.62 to 2.76; tenacity is brittle; non-magnetic; exhibits weak to moderate blue or multi-colored fluorescence under UV light.
Optical Properties
Refractive index ranges from 1.520 to 1.550; doubly refractive (biaxial); exhibits strong adularescence (schiller effect) caused by the light scattering between microscopic lamellae of albite and orthoclase.
Hardness & Durability
Origin Region
Madagascar, India, Sri Lanka, Australia, and the United States. Typically found in igneous and pegmatitic geological environments.
Hardness & Durability
Mohs hardness of 6 to 6.5; moderate toughness but sensitive to sharp blows due to two distinct cleavage planes; fair durability making it suitable for pendants and earrings, but requires care in rings.
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid ultrasonic cleaners, steam cleaners, and harsh chemical detergents. Store separately in a soft pouch away from harder gemstones to prevent scratching.
Rarity & Value
Common to Uncommon depending on the quality of the adularescence and clarity; value is determined by the intensity of the blue or rainbow sheen, transparency, and minimal distracting inclusions, ranging from affordable for polished spheres to moderately high for top-grade gem cabs; generally untreated.
Special Characteristics
Exhibits strong adularescence (a floating blue or multi-colored sheen) caused by light interference within micro-lamellar structures, coupled here with striking dark mineral inclusions creating a unique scenic pattern.
Lore & History
Historically associated with lunar deities and used as a protective talisman for travelers and lovers. In modern crystal healing, it is traditionally linked to the Third Eye and Crown chakras, believed to promote intuition, emotional balance, and new beginnings, though these are cultural and traditional beliefs rather than scientific claims.