Labradorite is a calcium-enriched plagioclase feldspar, part of the abundant feldspar mineral family. It is prized for labradorescence, an optical phenomenon also known as the schiller effect. This effect causes a brilliant, iridescent flash of color—often blue, green, gold, and red—to appear when light strikes the stone at certain angles.
Major Global Natural Deposits
Labradorite was first documented in 1770 on Paul’s Island near Nain, located on the Labrador Peninsula in Canada, which gave the mineral its name. This original location remains an important source, yielding stones with deep blue and green iridescence. Finland produces Spectrolite, a variety distinguished by its particularly vibrant, full-spectrum display of labradorescence. Madagascar is one of the most prolific modern sources, supplying large volumes of gray to black material that exhibits strong color flashes. Other established mining regions include Russia, specifically the Kola Peninsula, and Norway, where specimens are found within anorthosite masses.
Geological Settings and Identification
Labradorite forms primarily in specific types of igneous rocks that cool from molten magma deep beneath the Earth’s surface. It is commonly found within mafic igneous rocks, which are rich in magnesium and iron, such as basalt, gabbro, and norite. However, the most commercially significant deposits occur in a rock type almost entirely composed of plagioclase feldspar called anorthosite.
The characteristic labradorescence is not caused by pigmentation, but by the physical structure of the mineral itself. The effect is produced by the scattering of light off microscopic, alternating layers of different feldspar compositions within the crystal structure, known as exsolution lamellae. These thin layers interfere with the light waves, causing a flash of spectral color that shifts as the stone is tilted.
When identifying labradorite, look for large, blocky grains embedded in the host rock. The mineral typically appears clear, white, or a dull gray until the optical effect is activated. It is a moderately durable mineral, ranking between 6 and 6.5 on the Mohs hardness scale, comparable to quartz. A key physical trait is its cleavage, as it tends to break along two prominent planes that meet at an angle slightly deviating from 90 degrees.
Acquiring Labradorite Commercially
The commercial market offers a wide variety of rough and finished labradorite material. E-commerce platforms are accessible avenues, featuring sellers offering everything from raw specimens to polished cabochons. When purchasing online, scrutinize seller ratings and product descriptions to assess quality and origin.
Specialized venues, such as gem and mineral shows, allow buyers to inspect the labradorescence firsthand, which is crucial for evaluation. Local rock shops and lapidary suppliers also stock the stone, catering to jewelry makers and collectors. Price is largely determined by the vibrancy and coverage of the color flash; material exhibiting a full-spectrum or intense blue flash commands a higher value.