Scientific Name: Plagioclase feldspars
Group: Silicates - tectosilicates
Chemical composition: NaAlSi3O8CaAl2Si2O8
Colors: Blue, gray, white
Hardness: 6 to 6.5
Formation: Triclinic crystal; usually massive form
Principal Sources: Madagascar, Finland, Russia, Southern India, Mexico, US
Special Notes: Labradorite occurs in large crystal masses in anorthosite and shows a play of colors called labradorescence. The labradorescence, or schiller effect, is the result of light refracting within lamellar intergrowths. High quality specimens are called spectrolite.