Labradorite as a Gemstone
Labradorite has become a popular gemstone because of the unique iridescent play-of-color that many specimens exhibit. The quality, hue, and brilliance of the labradorescence varies from one specimen to another and within a single specimen. Stones with exceptional color are often given the name “spectrolite.”
Labradorite is rarely seen in mass-merchant jewelry. Instead it is most often used by designers and jewelers who do unique and custom work.
Many specimens of labradorite do not exhibit labradorescence. These materials can still produce beautiful gemstones because of their desirable color or other optical effects such as aventurescence. A beautiful orange piece of labradorite cut as a faceted stone is shown on this page.
Some specimens of sunstone are labradorite. Sunstone is a plagioclase gemstone in which tiny platelets of copper or another mineral are arranged in a common orientation. These platelets produce a reflective flash when incident light enters the stone at a proper angle relative to the angle of observation.
Some cautions are required when using labradorite as a gemstone. It breaks in two directions with perfect cleavage. This makes it subject to breaking with impact and not a good candidate for jewelry or other objects that could be subject to impact. It also has a hardness of 6 on the Mohs scale. It will therefore scratch much more easily than diamonds, rubies, sapphires, and emeralds, and slightly more easily than jasper and agate.
Labradorescent material is most often cut into cabochons. The labradorescence phenomenon is best exhibited when the base of the cabochon is parallel to the layers in the material that produce the labradorescent flash.
Careful study of the material is required so that the finished stone will be oriented to produce a full “face-up color.” If the stone is cut at any other angle, the layers that produce the labradorescence will be inclined when the stone is viewed from directly above. This will yield a labradorescent flash that will appear to be off-center.
Geologic Occurrence of Labradorite
Labradorite is found in igneous, metamorphic, and sedimentary rocks. It most often occurs as a primary mineral in mafic igneous rocks such as basalt, gabbro, and norite. It is also found in anorthosite, an igneous rock in which labradorite can be the most abundant mineral. Labradorite occurs in gneiss that has been produced through the metamorphism of labradorite-bearing igneous rocks. It is also found in sediments and sedimentary rocks that are derived from the weathering of other rocks that contain labradorite.
Notable Labradorite Localities
Labradorite is named after its location of discovery on the Isle of Paul, near Nain, Labrador, Canada. It was discovered there in 1770 by a Moravian missionary.
Labradorite with superb labradorescence is produced from a few deposits in Finland. The best of this material was given the name “spectrolite” by the director of the Geological Survey of Finland. Today, specimens of labradorite with exceptional labradorescence from other locations are frequently called “spectrolite.”
A significant amount of gray to black labradorite with good labradorescence is produced from locations in Madagascar and Russia. Small amounts of transparent labradorite with internal color flash are produced in India.
Several mines in Oregon produce transparent orange, yellow, red, blue, green, and clear labradorite without labradorescence. These can be cut into very nice faceted stones. Some of this material has platy inclusions of copper in a common alignment that can produce an aventurescent flash when played in the light. These materials are marketed under the name “Oregon Sunstone” and have attracted a strong following from local designers and the tourist trade.