Labradorite
Plagioclase Feldspar var. Labradorite · Semi-Precious Gemstone; Collector Mineral
Crystal System
Triclinic; typically occurs in massive or granular habits, rarely as distinct tabular or prismatic crystals.
Mineral Group
Silicates (Tectosilicates); Feldspar Group; Plagioclase Series
Chemical Formula
(Ca, Na)(Al, Si)4O8 (specifically 50-70% calcium to 30-50% sodium)
Formation Process
Igneous formation; crystallizes from cooling magma in gabbro or norite. It can also form during metamorphism in amphibolite rocks.
About This Crystal
A dark, smoky-gray to greenish-black base color with an iridescent metallic luster. It is translucent to opaque with a vitreous to pearly luster on cleavage surfaces, often showing internal fractures and twinning lines.
Physical Characteristics
Body color is gray/brownish-black with a white streak. Possesses perfect cleavage in two directions at nearly 90 degrees and conchoidal to uneven fracture. Specific gravity is 2.68–2.72. May show weak fluorescence under UV.
Optical Properties
Displays Labradorescence (a form of schiller effect) caused by light scattering off sub-microscopic exsolution lamellae. Biaxial (+) or (-), refractive index 1.559–1.573, low birefringence.
Hardness & Durability
Origin Region
Notable sources include Labrador (Canada), Madagascar, Finland (Spectrolite variety), Russia, and Australia. Usually found in mafic igneous rocks.
Hardness & Durability
Mohs hardness of 6.0–6.5. It is brittle with fair toughness; its perfect cleavage makes it susceptible to cracking if struck hard. Good for jewelry with protective settings.
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid ultrasonic or steam cleaners. Sensitive to sudden temperature changes and some acids. Store separately to prevent scratching from harder stones like quartz.
Rarity & Value
Common globally, but high-quality specimens with full-spectrum 'Spectrolite' flash are more valuable. Generally affordable; value is determined by the intensity, variety of colors in the flash, and lack of dark 'dead' spots.
Special Characteristics
The primary feature is Labradorescence, an optical phenomenon where colors shuffle as the stone is rotated. Some specimens may also show aventurescence if copper or hematite inclusions are present.
Lore & History
First identified in Labrador, Canada, in 1770. Inuit legend claims the Northern Lights were trapped inside the rocks. In modern crystal lore, it is known as a 'Stone of Transformation' associated with the Third Eye and Throat Chakras.