Grey feldspar that flashes blue and gold from one angle only. The flash is structural, and it cannot be dyed in.
Madagascar, Finland (spectrolite), Labrador in Canada, Russia5 field tests
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Labradorite is a plagioclase feldspar whose appeal has nothing to do with its body colour, which is an unremarkable grey to grey-brown. What it has instead is labradorescence: a broad flash of blue, green, gold or occasionally violet that appears when the stone is held at one particular angle and vanishes at every other.
The effect is structural rather than chemical. The mineral separated internally into alternating microscopic lamellae as it cooled, and light interfering between those layers produces the colour, in the same way an oil film on water does. That is a useful fact for identification, because a structural colour behaves in a way no dye or coating can imitate: it must switch off when you tilt the stone.
That single behaviour is nearly the whole identification. Everything else — hardness 6 to 6.5, two cleavage directions meeting at close to ninety degrees, a specific gravity around 2.70 — is standard feldspar and shared with a dozen relatives.
Hold the stone under a single light source and rotate it slowly through a full turn, then tilt it. Genuine labradorescence appears abruptly across a broad area, holds for a narrow range of angles, and disappears completely. It is a sheet of colour rather than a sparkle, and it lies below the surface.
Dyed, coated and glass imitations get this wrong in a consistent way: their colour either persists from every direction, or sparkles as discrete points rather than sweeping as a sheet, or sits visibly on the surface where it can be worn through at an edge.
| Property | Labradorite | Imitation behaviour |
|---|---|---|
| Colour flash | Broad sheet, one angle only, then gone | Persists from all angles, or glitters as points |
| Where the colour lies | Below the surface, within the stone | On the surface; wears through at edges |
| Mohs hardness | 6 – 6.5 | Glass about 5.5; plastic far softer |
| Specific gravity | 2.68 – 2.72 | Glass and resin differ |
| Cleavage | Two directions, near 90° | Glass has none |
| Body colour | Grey to grey-brown, sometimes near-black | Dyed material often has vivid body colour |
| Fine internal striations | Present — the lamellae, visible at 10× | Absent in glass |
The one-angle rule is close to conclusive. A stone whose blue is visible from everywhere is not showing labradorescence, whatever it is.
Ordered by how much each one proves. The decisive tests are worth your first two minutes; the supporting ones only matter once those agree.
Rotate and tilt the stone under a single light. Genuine labradorescence appears as a broad sheet of colour within a narrow angular window and then switches off entirely, leaving plain grey. Colour that follows you around the room is body colour, and labradorite's body colour is grey. This is the test, and it takes five seconds.
Coated imitations show their true colour where the coating stops or has worn — at a drill hole, a chipped edge, or the contact point of a bead that has been worn. Labradorescence has no edge because it is generated inside the stone.
Feldspar cleaves in two directions meeting at close to a right angle, so broken labradorite shows flat rectangular steps and often fine parallel striations on a cleavage face — the twinning lines characteristic of plagioclase. Glass has no cleavage and shows conchoidal breaks with round bubbles inside.
Labradorite will just scratch a glass plate and a steel knife will not cut it, though a hard file will. Glass imitations at 5.5 will not scratch glass. This is a supporting check rather than a decisive one, because the difference is small.
At 10× magnification the flashing areas often reveal extremely fine parallel internal striations — the lamellar structure that generates the colour. Their presence confirms the mechanism; their absence in a stone that flashes suggests a coating or a foil backing.
Each of these is checked differently. The ones with their own page have enough that is specific to them to be worth reading separately.
Specimen figures rather than gem figures, for material in honest condition. Most finds are worth very little, and saying so plainly is more useful than encouraging you.
| Form | What it typically fetches | Note |
|---|---|---|
| Tumbled labradorite | $2 – 10 | Abundant from Madagascar |
| Polished freeform or slab | $15 – 90 | Flash coverage and strength |
| Good cabochon, strong blue | $20 – 120 | Orientation and coverage |
| Fine spectrolite, full spectrum | $80 – 400 | Colour range plus Finnish origin |
Labradorite is priced almost entirely on the flash: how saturated it is, how much of the face it covers, and how many colours appear. Cutting orientation matters as much as the rough.
Lovenhall StoneThe tests tell you what it is. The instrument reads a photograph and offers a name to start from — then hands you back to the tile and the coin, which are what settle it.