Labradorite
Anorthite var. Labradorite (Plagioclase Feldspar) · Semi-Precious Gemstone / Collector Mineral
Crystal System
Triclinic; typically occurs as massive, granular, or tabular crystals, though the tumble shown hides the raw habit.
Mineral Group
Silicates (Tectosilicates); Plagioclase Feldspar group
Chemical Formula
(Ca,Na)(Al,Si)4O8
Formation Process
Igneous formation; crystallizes from cooling magma primarily in mafic igneous rocks such as basalt or norite.
About This Crystal
A dark gray to grayish-green base color with a vitreous (glassy) luster. This specimen is translucent to opaque and appears to be a tumbled stone showing subtle hints of internally reflected color.
Physical Characteristics
Color: Dark gray/green; Streak: White; Cleavage: Perfect in two directions roughly at 90 degrees; Fracture: Uneven to conchoidal; Specific Gravity: 2.68–2.72; Fluorescence: Weak yellow or blue under UV.
Optical Properties
Refractive Index: 1.560–1.572; Birefringence: 0.008–0.010; Notable for Labradorescence (a schiller effect caused by internal lamellar twinning which reflects spectral light).
Hardness & Durability
Origin Region
Notably Labrador, Canada; also Madagascar, Finland (Spectrolite), Russia, and Australia.
Hardness & Durability
Mohs hardness 6.0–6.5; brittle toughness; sensitive to pressure and rapid temperature changes; fair durability for jewelry.
Care & Maintenance
Clean with warm soapy water and a soft brush; avoid ultrasonic cleaners and steam cleaning; store separately from harder gems like quartz or diamonds to prevent scratching.
Rarity & Value
Relatively common; value is determined primarily by the intensity, range, and directionality of the 'flash' or labradorescence; tumbled pieces are very affordable.
Special Characteristics
Labradorescence: The unique play-of-color resulting from light interference within microscopic layers of alternating feldspar compositions.
Lore & History
Discovered in 1770 on Paul Island, Labrador. Inuit legend suggests the Northern Lights were trapped within the rocks. Traditionally used as a 'stone of transformation' and associated with the Third Eye chakra.