Geological Properties Of Labradorite

 

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.

Labradorite is a type of feldspar. Feldspar is found all over the world in all types of rock formation, igneous, metamorphic and sedimentary. Feldspar is made up of silica and aluminum and forms in a number of ways, including crystallization of magma or lava, being subject to high temperatures and great pressure below the earth’s surface or crushed together in sedimentary rock.

Labradorite is created when heat and pressure melt and mix various rocks and minerals. As the newly mixed materials slowly cool, the minerals separate into layers and this now, igneous rock, hardens with several inclusions. It is the layers that will later give the gemstone its shimmering color play.

This layering or lamellar separation only occurs with a particular mineral combination and so long as the rock cools over a very long time period. The wrong combination, or cooling too quickly, can create similar rocks but lack the shimmering play of color that identifies Labradorite gemstones.

Labradorite is one of nature’s most captivating feldspar minerals, celebrated for its extraordinary play of color known as labradorescence — a spectral display of shifting blues, greens, golds, and violets that shimmer across its surface as light moves. This phenomenon gives Labradorite an otherworldly beauty and a mystique that bridges both science and spirit.

Geologically, Labradorite is a calcium-sodium feldspar, specifically a member of the plagioclase feldspar series, with a chemical composition between anorthite (CaAl₂Si₂O₈) and albite (NaAlSi₃O₈). Its typical composition can be represented as (Ca,Na)(Al,Si)₄O₈. It belongs to the triclinic crystal system, often forming tabular or blocky crystals with a glassy to pearly luster and a hardness of 6–6.5 on the Mohs scale.

The mineral is usually gray to gray-green in base color, but when light enters the crystal and reflects off internal lamellar structures (thin, repeating planes within the mineral), it produces a stunning iridescence that seems to glow from within — the defining hallmark of Labradorite.

 

Formation and Occurrence

Labradorite forms in igneous rocks, primarily mafic to intermediate compositions such as gabbro, basalt, and anorthosite. It crystallizes deep within the Earth’s crust as molten magma slowly cools, allowing feldspar minerals to separate and form layered crystal structures. These internal lamellae, created during the cooling process, are what later generate its vibrant optical effect.

Over geological time, Labradorite-bearing rocks can also appear in metamorphic environments, where heat and pressure reorganize the mineral structures, enhancing their internal sheen. Weathered fragments of Labradorite can be found in sedimentary deposits, transported by erosion from their original host rocks.

Some of the most striking specimens occur in anorthosite formations, coarse-grained igneous rocks composed almost entirely of plagioclase feldspar. These ancient rock bodies are often more than a billion years old, linking Labradorite to some of the oldest crustal materials on Earth.

 

Color and Labradorescence

The true magic of Labradorite lies in its optical phenomenon of labradorescence — a play of color caused by light interference within the crystal’s lamellar twinning structures. When light enters the stone, it refracts and reflects between microscopic layers of differing refractive indices, producing brilliant flashes of color that appear to move as the stone is rotated.

• Blue and Green Flashes: Most common; produced by interference of shorter wavelengths of light.
• Gold and Orange Flashes: Result from thicker lamellar spacing.
• Purple, Pink, and Red Flashes: Rarest; caused by complex light interactions and trace mineral inclusions.

This iridescence is purely geological — a product of internal order and structure formed through precise cooling conditions deep within the Earth.

 

Notable Localities

Labradorite was first discovered in 1770 on the Isle of Paul (now part of Labrador, Canada) — the source of its name. Since then, it has been found in several parts of the world, each location producing specimens with unique color ranges and intensity of labradorescence.

• Canada (Labrador): The original and classic source, known for deep blue and gold flashes.
• Finland: Produces Spectrolite, a high-grade variety with full-spectrum color displays.
• Madagascar: Known for large, gemmy slabs with vivid blues and greens.
• Norway: Found in ancient anorthosite deposits.
• United States: Deposits in Oregon yield “Oregon Sunstone,” a related feldspar that sometimes displays aventurescence (sparkling inclusions).
• Russia and India: Notable for ornamental-grade material used in carvings and jewelry.

 

Labradorite Discovery and History

Labradorite was known as fire stone or fire rock by the native Inuit people of Canada and was the subject of some legends and customs but it was not until 1770 that is was officially identified as Labradorite.

It was ‘discovered’ by Moravian missionaries on the Isle of Paul in Labrador (hence its name) who began to trade Labradorite gemstones with British merchants for vital supplies to ensure the mission’s survival.

The spectacular Spectrolite was discovered in Finland by accident when soldiers were making obstacles for invading Russian tanks. While blowing up rocks with dynamite they discovered this brightly colored version of Labradorite.

 

What Causes Labradorescence

Labradorescence is not a display of colors reflected from the surface of a specimen. Instead, light enters the stone, strikes a twinning surface within the stone, and reflects from it. The color seen by the observer is the color of light reflected from that twinning surface. Different twinning surfaces within the stone reflect different colors of light. Light reflecting from different twinning surfaces in various parts of the stone can give the stone a multi-colored appearance.

 

Properties of Labradorite

Labradorite is a mineral in the plagioclase series, and it shares many of the properties of plagioclase minerals. It has a Mohs hardness of about 6 to 6 1/2 and two distinct directions of cleavage that intersect at an angle of about 86 degrees or 94 degrees. Plagioclase minerals frequently exhibit twinning and striations on cleavage faces.

Labradorite is the only mineral in the plagioclase series that exhibits strong labradorescence; however, many specimens of labradorite do not exhibit the phenomenon. Without seeing labradorescence, distinguishing labradorite from other members of the plagioclase series can be difficult. The methods used for distinguishing them are x-ray diffraction, chemical analysis, optical tests, and specific gravity determinations on pure specimens.

 

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.

 

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.

 

Countries of Origin

Myanmar; Cameroon; Papua New Guinea; Paraguay; Portugal; Greece; Mongolia; El Salvador; Korea (the Republic of); Morocco; Unknown; Brazil; Chile; Nepal; Tonga; United States of America (the); Hungary; Japan; Ukraine; Taiwan (Province of China); India; New Zealand; Canada; Namibia; Finland; Italy; Peru; Ethiopia; Germany; Tanzania, United Republic Of; Czechia; Egypt; Madagascar; Thailand; Costa Rica; Saudi Arabia; Sweden; Pakistan; China; Russian Federation (the); Poland; Slovakia; France; Kyrgyzstan; United Kingdom of Great Britain and Northern Ireland (the); Dominican Republic (the); Spain; Cuba; Saint Lucia; Norway; Mexico; Israel; Greenland; Tajikistan; Indonesia.

 

Labradorite: The Stone of Aurora and Light

Labradorite’s unique optical dance mirrors the interplay of Earth’s elements — fire, water, air, and mineral structure converging to create living light within stone. Its luminous sheen evokes the aurora borealis, the Northern Lights — a fitting connection, given its discovery in the far north.

From a geological perspective, it is a story of order and transformation, where cooling magmas and slow crystallization give rise to a mineral of mesmerizing depth and symmetry. Labradorite reminds us that beauty is often born from balance — the meeting of chemistry, structure, and time.

 

Physical Properties of Labradorite

Color: Usually clear, white, or gray in reflected light. Labradorescent colors can include blue, green, yellow, orange, and red.

Streak: White

Luster: Vitreous, pearly on cleavage faces

Diaphaneity: Transparent to translucent

Cleavage Two directions of perfect cleavage intersecting at about 86 degrees

Mohs Hardness: 6 to 6.5

Specific Gravity: 2.68 to 2.72

Chemical Composition: (Na,Ca)(Al,Si)4O8 with Na (30-50%) and Ca (70-50%)

Crystal System: Triclinic

 

At Crystals by Rob

At Crystals by Rob, we celebrate Labradorite as one of Earth’s most enchanting gifts — a mineral that bridges science, spirit, and light. Each piece in our collection is chosen for its vibrant labradorescence and natural authenticity, honoring both its geological origins and its ethereal presence. Labradorite reflects the magic hidden within the Earth’s depths — and within ourselves — a reminder that light and color are always waiting just beneath the surface.