Labradorite
Feldspar var. Labradorite · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Triclinic; typically occurs as massive, granular, or blocky individuals, often showing polysynthetic twinning.
Mineral Group
Silicates (Subgroup: Tectosilicates / Plagioclase Feldspar Group)
Chemical Formula
(Ca,Na)(Al,Si)4O8 (intermediate member of the plagioclase series)
Formation Process
Igneous; crystallizes from cooling magma in gabbro or norite. Can also form in some metamorphic environments through recrystallization.
About This Crystal
Opaque to translucent dark gray-green or dark blue-black base color. Displays a spectacular play of iridescent colors (labradorescence) when viewed at certain angles. Luster is vitreous to pearly on cleavage faces.
Physical Characteristics
Color: Dark gray to black; Streak: White; Cleavage: Perfect in two directions at 86 degrees; Fracture: Uneven to conchoidal; Specific Gravity: 2.68-2.72; Fluorescence: Generally inert.
Optical Properties
Refractive Index: 1.560-1.572; Birefringence: 0.008-0.010; Optical Phenomenon: Labradorescence (interference of light in sub-microscopic lamellar structures of exsolution).
Hardness & Durability
Origin Region
Notable sources include Labrador (Canada), Madagascar, Finland (Spectrolite), and Russia. Forms in mafic igneous rocks and metamorphic rocks.
Hardness & Durability
Mohs Hardness: 6.0-6.5; Toughness: Brittle; Cleavage makes it prone to splitting if struck. Limited durability for rings, better for pendants.
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid ultrasonic or steam cleaners. Sensitive to sudden temperature changes and strong acids. Store away from harder gems like sapphires.
Rarity & Value
Common in lower grades; High-quality specimens with 'spectrolite' range or full-spectrum flash are Uncommon. Value depends on intensity and range of flash.
Special Characteristics
Labradorescence: metallic-looking flashes of blue, green, gold, and orange caused by internal light scattering (Schiller effect).
Lore & History
Discovered in 1770 on the Labrador Peninsula. Inuit legends claim the northern lights (Aurora Borealis) were trapped inside the stones. Modernly known as a 'stone of transformation' or protection.