Labradorite
Image: Shannon Heinle (CC0)
Mineral NameLabradorite
Chemical Formula(Ca,Na)(Si,Al)4O8
Mohs Hardness6.5
Crystal Systemtriclinic
Lustervitreous
Streak Colorwhite
Cleavageperfect in two directions (pinacoidal)
Fractureuneven to conchoidal
Specific Gravity2.7
Colorsblue, violet, green, yellow, orange, grey
Transparencytranslucent to opaque
Type LocalityLabrador, Canada
Mineral GroupSilicates (Feldspar Group, Plagioclase Series)
Usesjewelry, ornamental stone, collector
Associated Mineralspyroxene, amphibole, olivine, magnetite
Raritycommon
Description
Labradorite is known for its striking play of colors, called labradorescence, which ranges from blues and violets to greens, yellows, and oranges. This iridescent effect is visible across cleavage planes and in sliced sections.
Geological Context
Labradorite is a plagioclase feldspar that forms in mafic igneous rocks such as gabbro, basalt, and anorthosite. The labradorescence is caused by light interference from microscopic lamellar intergrowths of different plagioclase compositions within the crystal.
