Labradorite (Ca,Na)(Al,Si)₄O₈ is a calcium-rich plagioclase feldspar famous for its iridescent labradorescence — a vivid blue, green, gold, and purple flash from light interference within microscopic exsolution lamellae. Discovered in 1770 in Labrador, Canada, and now sourced primarily from Madagascar (Tulear) and Finland (spectrolite variety).
Key Facts
- Mohs hardness 6–6.5.
- Triclinic plagioclase; intermediate Ca-Na composition (An50–70).
- Labradorescence is the diagnostic optical effect — schiller from periodic exsolution lamellae.
- Spectrolite (Finnish variety) shows the full color range; Madagascar material is dominantly blue.
- Major rock-forming mineral in mafic and intermediate igneous rocks.
Notable Localities
Tulear (Madagascar) and Ylämaa (Finland, spectrolite) lead production. Nain and Tabor Island (Labrador, Canada) are the type-localities. Russia (Karelia) yields collector specimens.
Found at these Localities
- Labrador Coast (Tabor Island, Nain) (拉布拉多海岸(拉长石产地))
