Labradorite | Rock Encyclopedia

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Stone of the dayEudialyteLove · SpiritEudialyte is a complex silicate that can give alkaline rocks streaks and masses of rose red. It belongs to a group of similar minerals, so a red specimen photograph may need a broader group label.Read about itkevinzim · CC BY 2.0

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Photo: James St. John · CC BY 2.0

Plagioclase feldspar compositional variety

plagioclase feldspar
plagioclase
feldspar

In folklore

Labradorite is a calcium-rich plagioclase feldspar that can flash blue, green or other colours when turned in the light. The effect, labradorescence, comes from fine internal layers rather than paint on the surface. The name covers a composition range within the feldspar series, so a photograph cannot confirm its exact chemistry.1 2

At a glance

Composition: (Ca,Na)[Al(Al,Si)Si₂O₈]calcium-sodium aluminosilicate
Colour: Grey, pale green, blue, white
Luster: Subvitreous; iridescent on some faces
Hardness: 6–6.5Mohs
Crystal system: Triclinic
Transparency: Translucent to opaque
Streak: White

Many pieces look plain grey or dark until one face catches the light. Then a broad sheet of blue, green, gold or mixed colour may appear and vanish with a small change in viewing angle. Move the specimen or camera slowly instead of relying on a single front-facing image. In rough rock, look for blocky feldspar grains and flat cleavage faces; a polished slab may show a patchwork of flashing areas separated by dark boundaries. Not every labradorite shows a dramatic flash, and the strength of the effect depends on crystal orientation and cut. A bright photograph may exaggerate saturation, while a poorly angled photograph may hide a real effect. The flash is useful evidence but does not alone prove species, source or whether a piece has been treated.1 2 3

Moonstone is another feldspar with a shifting sheen, but its characteristic glow is usually softer and cloud-like rather than a broad, sharply coloured flash. Iridescent glass and coated stones can show conspicuous colours too, though their internal structure differs. Ordinary feldspar in the same rock may be grey and blocky without labradorescence. A polished piece can obscure cleavage and other context, so a difficult gem needs proper optical and chemical examination, especially when a name such as “blue moonstone” is used in trade.1 2 4

Labradorite commonly crystallises as part of an igneous rock while molten material cools. It is a member of the albite–anorthite plagioclase series: calcium and sodium proportions vary rather than making every grain chemically identical. On further cooling, extremely fine layers of differing composition can develop inside some crystals. Light reflected by those layers produces labradorescence when their spacing and viewing angle are suitable. The original feldspar grains can later become part of metamorphic rocks or weather out of an older rock. The colour effect therefore tells something about internal structure, but it does not give a simple clock for when the surrounding rock formed.1 2 5

The named early occurrence is Ford Harbour on Paul Island in Labrador's Nain Complex, Canada. Plagioclase of this composition also occurs in igneous rocks elsewhere, including anorthosite and gabbro; USGS describes labradorite-rich rocks in the California Coast Ranges. Collectible material is traded from several countries, but a sample's grey body and blue flash cannot establish which one. Preserve its field or purchase documentation rather than guessing its origin from colour.1 5 6

Labradorite with an attractive flash is cut into cabochons, beads and polished decorative slabs. A cutter must orient the surface so the colourful reflection is visible; the same rough block can look very different after rotation. GIA describes the related Finnish trade material “spectrolite” as a labradorite displaying especially broad colour. Feldspar-rich stone is also used decoratively as building or interior material where its appearance and physical suitability fit the job. A display slab and a jewellery stone have different wear risks, and neither should be assessed only by the brightest online image.2 3 7

Labradorite takes its name from Labrador, where early mineralogical descriptions came from material in the Nain area. It is now a mineralogical name for a compositional interval of plagioclase rather than proof that every specimen was collected in Labrador. In 2019, Jason Sikoak, an Inuit artist from Rigolet, Nunatsiavut, published a story in Inuktitut magazine about colour remaining in a coastal stone after a hunter released stolen northern lights. That authored retelling is a valuable, traceable cultural source; it should not be flattened into a timeless claim that all Inuit communities tell exactly the same version.1 8

The visible strength, coverage and orientation of the flash can influence collector and jewellery interest, along with size, cut, fractures and documented origin. Labradorite has cleavage planes along which a blow can break it; GIA lists feldspar gems in this hardness range as relatively poor in toughness. Keep polished pieces apart from harder stones, avoid knocks, and clean gently with a soft cloth and mild soapy water if the setting allows. Heat and harsh equipment are poor choices for an uncertain gem. Some feldspar material can be colour-treated, so a photograph cannot certify a natural colour, exact identity or value.1 4 10

“Labradorite” — Mindat.org. Accessed 2026-10-01.Open source
“Optical Effects of Phenomenal Cabochons” — Gemological Institute of America. Accessed 2026-10-01.Open source
“Labradorite” — Gemological Institute of America, Edward J. Gübelin Collection. Accessed 2026-10-01.Open source
“Moonstone Care and Cleaning Guide” — Gemological Institute of America. Accessed 2026-10-01.Open source
“Pre-Elsonian mafic magmatism in the Nain Igneous Complex, Labrador” — U.S. Geological Survey. Accessed 2026-10-01.Open source
“Quartz gabbro and anorthositic gabbro: Markers of offset along the San Andreas fault” — U.S. Geological Survey. Accessed 2026-10-01.Open source
“Guide to Phenomenal Gems” — Gemological Institute of America. Accessed 2026-10-01.Open source
“The Northern Lights of Nunatsiavut” — Jason Sikoak, Inuktitut magazine, Inuit Tapiriit Kanatami, Summer 2019. Accessed 2026-10-01.Open source
“Labradorite: Meaning, Properties, and Benefits You Should Know” — AllCrystal. Accessed 2026-10-01.Open source
“Gemstone Durability: Design to Display” — Gemological Institute of America. Accessed 2026-10-01.Open source

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