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.