What is labradorite?
Labradorite is a calcium-sodium feldspar in the plagioclase series. It may appear grey, dark or nearly colourless until light catches internal layers and produces labradorescence: flashes of blue, green, gold or warmer colours.
Mineralogy and structure
Labradorite is a silicate that crystallises in the triclinic system. It has Mohs hardness around 6-6.5 and two cleavage directions typical of feldspars. Its composition varies between calcium-rich and sodium-rich feldspar end-members, which is reflected in the formula used in the reference table.
Colour and appearance
The body colour is often grey to charcoal, while the optical flash is caused by light interacting with fine internal lamellae. The strength, colour and direction of the flash depend on the cut and viewing angle, so no two polished plates look identical.
Formation and localities
Labradorite is common in igneous rocks such as gabbro and anorthosite, and also occurs in some metamorphic rocks. Classic material is associated with Labrador in Canada; important ornamental sources also include Finland, Madagascar, Norway and Russia.
Use in collections and mosaic
Collectors value crystal faces with visible play of colour, while lapidary artists select material for broad, stable flashes. In mosaic and inlay, labradorite creates changing highlights that respond to the viewer's position and the direction of light.
