Labradorite
Labradorite (Plagioclase Feldspar) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Triclinic; typically found in massive or granular habits, rarely as distinct tabular or prismatic crystals
Mineral Group
Silicates; Subgroup: Tectosilicates (Feldspar group, Plagioclase series)
Chemical Formula
(Na,Ca)(Al,Si)4O8 containing between 50% and 70% calcium-rich anorthite
Formation Process
Igneous; forms during the crystallization of mafic igneous rocks such as basalt, gabbro, and norite, as well as in some metamorphic rocks
About This Crystal
An opaque to translucent dark grey or green-brown stone characterized by a greasy to vitreous luster. This specimen is polished into an oval cabochon or palm stone shape, showing internal twinning planes and dark veil-like inclusions.
Physical Characteristics
Body color ranges from dark grey to grey-green; Streak: White; Cleavage: Perfect in two directions at almost 90 degrees; Fracture: Uneven to conchoidal; Specific Gravity: 2.68–2.72; Fluorescence: Can show faint yellow or red under UV
Optical Properties
Refractive Index: 1.560–1.572; Birefringence: 0.008–0.010; Best known for 'Labradorescence' (a schiller effect caused by light diffraction within lamellar intergrowths); Doubly refractive
Hardness & Durability
Origin Region
Madagascar, Canada (Labrador), Finland (Spectrolite variety), Russia, and Australia
Hardness & Durability
Mohs Hardness: 6.0–6.5; Brittle toughness; sensitive to pressure and thermal shock due to its perfect cleavage planes
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid ultrasonic or steam cleaners; store separately from harder gems like quartz or sapphire to prevent scratching
Rarity & Value
Relatively common; value is determined by the intensity and spectrum of the labradorescence (flash), with multi-colored 'Spectrolite' from Finland being the most valuable
Special Characteristics
Labradorescence (optical interference of light); sub-microscopic exsolution lamellae (polysynthetic twinning) create the metallic-looking iridescent flashes of blue, gold, and green
Lore & History
First discovered in Labrador, Canada, in 1770. Inuit folklore claims northern lights were trapped within the rocks. In metaphysical traditions, it is known as a 'Stone of Transformation' associated with the Third Eye and Throat chakras.