Labradorite (Tumbled Stone)
Plagioclase Feldspar var. Labradorite · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Triclinic; typically found in massive habits or as rounded tumbled stones, showing polysynthetic twinning
Mineral Group
Silicates (Tectosilicates); Feldspar Group, Plagioclase Series
Chemical Formula
(Ca,Na)(Al,Si)4O8 with trace Fe, K, Ba
Formation Process
Igneous formation via crystallization from cooling magma in slow-forming plutonic environments or volcanic flows; can also occur in metamorphic rocks
About This Crystal
A translucent to opaque grey-green stone with a vitreous to pearly luster. This specimen is a small tumbled pebble showing a dark grey base with localized black inclusions and hint of labradorescence (schiller effect)
Physical Characteristics
Color: Dark grey/green; Streak: White; Cleavage: Two directions at nearly 90 degrees; Fracture: Conchoidal to uneven; Specific Gravity: 2.68-2.72; Fluorescence: Weak yellow/pink under UV
Optical Properties
Refractive Index: 1.559-1.573; Birefringence: 0.008-0.010; Notable for Labradorescence (internal light scattering from lamellar twinning); Biaxial positive/negative
Hardness & Durability
Origin Region
Notably Labrador (Canada), Madagascar, Finland (Spectrolite), and Russia; found in mafic igneous rocks like basalt and gabbro
Hardness & Durability
Mohs Hardness: 6.0 to 6.5; Toughness: Poor due to perfect cleavage; brittle; suitable for jewelry but requires protection from hard impacts
Care & Maintenance
Clean with warm soapy water and soft cloth; avoid ultrasonic or steam cleaners; sensitive to sudden temperature changes and strong acids; store separately to prevent scratching
Rarity & Value
Common; Value is determined by the strength and spectrum of 'flash' (labradorescence). Tumbled stones are inexpensive ($1-$5), while high-quality Spectrolite is rare and more valuable
Special Characteristics
Labradorescence: An interference effect that creates metallic flashes of blue, green, and gold when held at specific angles; may show dark ilmenite or magnetite inclusions
Lore & History
First identified in Labrador, Canada in 1770. Inuit lore claims it's the Northern Lights trapped in stone. Traditionally associated with the Third Eye chakra and believed to be a 'Stone of Magic' for protection and intuition