Labradorite
Image: Guy Courtois (CC BY-SA 3.0)
Mineral NameLabradorite
Chemical Formula(Ca,Na)(Al,Si)4O8
Mohs Hardness6
Crystal Systemtriclinic
Lustervitreous
Streak Colorwhite
Cleavageperfect in two directions at nearly 90 degrees
Fractureuneven
Specific Gravity2.7
Colorsgray, dark gray, black, greenish-gray, blue, green, yellow, orange, red
Transparencytranslucent
Type LocalityLabrador, Canada
Mineral GroupSilicates
Usesjewelry, ornamental, collector
Associated Mineralspyroxene, amphibole, magnetite, ilmenite
Rarityuncommon
Description
Labradorite is a dark feldspar mineral, typically gray to black, renowned for its striking iridescent play of colors known as labradorescence, which appears as flashes of blue, green, yellow, and sometimes red or purple. The pieces in the image are polished cabochons, showcasing this optical effect.
Geological Context
Labradorite forms in mafic igneous rocks such as gabbro, basalt, and anorthosite, as well as in some metamorphic rocks. Its characteristic iridescence is due to light interference within microscopic lamellar intergrowths of exsolved plagioclase phases.
