Cause of Color :
Play of color due to interference of light from twin planes.
Chemical Composition :
Aluminum silicate of potassium, sodium and calcium. KAlSi3O8. Isomorphous series made up of Albite (Na), Oligoclase, Andesine, Labradorite, Bytownite and Anorthite (Ca) where the two end member are NaAlSi3O8 and CaAl2Si2O8.
Crystal System / Forms :
Cuts & Uses :
Facetted, cabochon, beads and carving.
Oriented needles or platelets of magnetite, twin planes, fingerprints and crystal inclusions.
Optic Character :
Anisotropic, D.R.; Biaxial positive
In dark colored labradorite.
Refractive Index / Birefringence :
1.560 – 1.572 / 0.009
Simulants (with separation tests) :
- Transparent Labradorite from quartz (optic figure), scapolite (optic figure), beryl (optic figure), Iolite (pleochroism, inclusions, U.V. fluorescence)
- Spectrolite from black opal (R.I., S.G., structure)
U.S.A., India, Canada, Australia, Madagascar, Russia, Mexico.