Labradorite derives its name from the principal location that it is found, Paul's Island Labrador, a region of Atlantic Canada near the island of Newfoundland. Labradorite is a translucent to transparent mineral that occurs in crystalline masses, and occasionally in tabular crystals. Labradorite is a major constituent of medium to low silica metamorphic and igneous rocks such as andesite, basalt, diorite, and olivine gabbro.
A distinct characteristic of labradorite is its iridescent play of color (schiller effect) that occurs on cleavage surfaces. The schiller effect is caused by light being scattered from thin perthitic lamellar intergrowth layers of different feldspars that chemically separated during the cooling process. Specimens that display the schiller effect are usually cut en cabochon or as a flat plane.
Labradorite's principal base color is blue, but it can occur in a wide variety of colors such as green, orange, red, and yellow. There are gemstone varieties from Madagascar and transparent varieties from India. Gemstone varieties from Finland that have a high amount of iridescence are sometimes referred to as "Spectrolite." There is even a variety from Mexico that can be faceted.
Labradorite crystallizes in the triclinic crystal system with a massive crystal habit and crystal twinning is common. Labradorite has perfect cleavage. Labradorite is a hard material with a hardness of 6.0 to 6.5 on the Mohs scale. Labradorite has a refractive index of 1.560 to 1.570. Labradorite has a vitreous luster.
Chemical composition: (Ca,Na)(Al,Si)4O8
Semi-Precious Stones