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The name Labradorite comes from the Canadian province of Newfoundland and Labrador, which is a famous locality for the stone. The mineral was discovered by Moravian missionaries at Ford Harbour, Paul Island near Nain off the coast of Labrador in 1770. It is normally characteristic of gabbros and basalts and is the main constituent of the plutonic rock anorthosite. Most commonly used in jewelry and as dimension stone, labradorite is also used for industrial purposes such as in the production of glass.

According to an Eskimo legend, the Northern Lights were once imprisoned in the rocks along the Labrador coast, until one day an Eskimo warrior found them and freed most of the lights with a blow from his spear. Not all the lights could be freed from the stone however and for that reason we have today what is known as labradorite.

Labradorite is a member of the plagioclase series of minerals is comprised of feldspars that range in chemical composition from pure NaAlSi3 O8 called albite, to pure CaAl2 Si2 O8 called anorthite. Labradorite is defined at approximately the 50% to 70% CaAl2 Si2 O8. By definition it must contain 50-70% calcium to 50-30% sodium in the sodium/calcium position of the crystal structure. All members of the plagioclase series usually display lamellar twinning called "Albite Twinning". The twinning is caused by an error in the crystal structure during its growth.

The color display is from lamellar intergrowths inside the crystal. These intergrowths result from compatible chemistries at high temperatures becoming incompatible at lower temperatures and thus a separating and layering of these two phases. The resulting color effect is caused by a ray of light entering a layer and being refracted back and forth by deeper layers. This refracted ray is slowed by the extra travel through the layers and mixes with other rays to produce a light ray coming out that has a different wavelength than when it went in. The wavelength corresponds to the wavelength of a particular color. The effect depends on the thickness and orientation of the layers and also upon the angle of the viewer or the angle of the light source. If the layers are too thick or too thin, or if the angle of the viewer or light source is not correct then 'labradorescence' will not be seen.

Labradorite's crystal structure is triclinic, however crystals are very rare and are usually golden yellow and may be translucent. It is usually found as a compact aggregate and is sometimes opaque. It has a vitreous luster and is sensitive to pressure. The yellow striations sometimes fluoresce.

Though known by many other names, perhaps the most commonly used synonyms for labradorite are black moonstone, which is a darker variety of the mineral and Spectrolite, which is the term used for samples that come from Finland. Spectrolite was discovered by accident in 1940 during the Second World War, when stone was being quarried along Finland's eastern border for the purpose of making anti-tank obstacles. Typically, the labradorite mined from Finnish quarries is used for jewelry and is considered to be of gem quality.

Labradorite can be found in many places all over the world including; it's name sake, Labrador, other parts of Newfoundland and Canada, the United States, Mexico, South America and Norway. The most impressive pieces however come from Finland (Spectrolite) and Madagascar. Though most widely recognized for it's use in jewelry and as dimension stone, labradorite also has many industrial uses. Because it occurs in gabbros, which are widely used as crushed stone for road construction, it too is used as a road building material. Like other plagioclase feldspars, it can be used in the manufacture of ceramics acting to increase the strength and durability of ceramic and to cement the other constituent materials together. Also, because it has a ranged melting point it can be used as a fluxing agent to produce glassy phases in the ceramic.

During the 18th century, labradorite was one of the stones frequently used in jewelry in France and England. Pins, broaches, bracelets, etc. were often set with gems, the first letters of which formed a motto or expressed a sentiment. Labradorite was often used as the "L" in mottos like "Good Luck." It was customary to use labradorite in the representation of objects with a metallic color such as the iridescent wings of butterflies. In the beginning of the 19th century, reliefs of Mandrill baboons were very much in vogue, and labradorite was used to represent the color of their snouts.

From its discovery in Labrador in 1770 to present day, labradorite has fascinated both the amateur and the professional alike. It's plethora of uses in the jewelry and gem industries and high demand for labradorite as dimension stone make it one of the most popular and recognizable minerals in the world.