Rainbow Moonstone (Labradorite)
Feldspar var. Labradorite (Plagioclase Series) · Semi-Precious Gemstone / Collector Mineral
Crystal System
Triclinic; typically occurs in massive, granular, or blocky habits rather than distinct crystals
Mineral Group
Silicates (Subgroup: Tectosilicates; Plagioclase Feldspar Group)
Chemical Formula
(Ca,Na)(Al,Si)4O8 with trace K (Potassium)
Formation Process
Igneous formation; crystallizes from cooling magma in plutonic environments at high temperatures and pressures
About This Crystal
The specimen shows an opaque to translucent white base with a pearly to vitreous luster. It exhibits a distinct iridescent schiller effect on reflecting surfaces, characterized by multicolored flashes of blue, gold, and pink.
Physical Characteristics
White to colorless body; white streak; perfect cleavage in two directions; conchoidal to uneven fracture; specific gravity 2.68–2.72; non-magnetic; may show weak fluorescence.
Optical Properties
Biaxial (+); Refractive Index 1.560–1.568; Adularescence/Labradorescence (interference of light at thin, microscopic layers of exsolution lamellae within the feldspar)
Hardness & Durability
Origin Region
Madagascar, Bihar State of India, and Sri Lanka; found in anorthosite igneous rocks
Hardness & Durability
Mohs hardness 6 to 6.5. Fair toughness; vulnerable to pressure due to perfect cleavage. Suitable for jewelry with protective settings.
Care & Maintenance
Clean with warm soapy water and a soft brush; avoid ultrasonic or steam cleaners. Store separately from harder stones like sapphire to prevent scratching.
Rarity & Value
Moderately common; value is determined by the intensity and 'fire' of the adularescence. High-clarity specimens with strong blue or rainbow flashes are most valued.
Special Characteristics
Displays 'labradorescence' (rainbow optical phenomenon); visible lamellar twinning; internal fractures which contribute to light scattering.
Lore & History
Traditionally associated with the moon and divine feminine energy. In modern crystal healing, it is used for intuition and balancing emotions. Historically used in jewelry since the Art Nouveau period.