Labradorite formed through the slow crystallization of feldspar within large igneous intrusions during the Precambrian era, roughly 1-4 billion years ago. The mineral developed as magma cooled gradually within massive anorthosite complexes—geological formations composed almost entirely of feldspar minerals.
The stone's distinctive optical property, labradorescence, results from a process called exsolution that occurred during cooling. As temperatures dropped over geological time, the original feldspar separated into alternating microscopic layers of calcium-rich and sodium-rich plagioclase. These extremely thin layers, measuring only 100-300 nanometers thick, create interference patterns that diffract white light into spectral colours.
Labradorite was first identified in Labrador, Canada in 1770, from where it gained its name.
