igneous
Labradorite (Larvikite variety)
Plagioclase Feldspar (Na,Ca)(Al,Si)4O8 with Monzonite/Syenite matrix
Hardness: 6.0-6.5; Color: Dark grey to black with blue/silver iridescent patches; Luster: Vitreous to pearly; Crystal structure: Triclinic; Specific gravity: 2.68-2.72; Cleavage: Perfect in two directions at nearly 90 degrees.
- Hardness
- 6
- Color
- Dark grey to black with blue/silver iridescent patches
- Luster
- Vitreous to pearly
Identified More igneous →
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Physical properties
Hardness: 6.0-6.5; Color: Dark grey to black with blue/silver iridescent patches; Luster: Vitreous to pearly; Crystal structure: Triclinic; Specific gravity: 2.68-2.72; Cleavage: Perfect in two directions at nearly 90 degrees.
Formation & geological history
Formed from the slow cooling of magmatic melts deep in the Earth's crust (intrusive). The iridescent effect (labradorescence) is caused by light diffraction in regular layers of different compositions (lamellae) that develop during cooling.
Uses & applications
Used widely for architectural cladding, high-end kitchen countertops, monuments, and as a semi-precious gemstone for jewelry and decorative carvings.
Geological facts
This specific variety is often marketed as 'Blue Pearl Granite' even though it is geologically a Larvikite. It is the national stone of Norway. The labradorescence seen in the flashes of color is due to the Schiller effect.
Field identification & locations
Identify in the field by rotating the dark, coarse-grained rock under light to find the 'flash' of blue or silver. It is commonly found in the Larvik region of Norway and parts of Canada, Madagascar, and Russia.
