How to tell if labradorite is real
Real labradorite flashes from inside the stone at set angles, with straight-edged colour zones and hardness 6 to 6.5. Larvikite and coated glass do not.
To tell if labradorite is real, tilt it under one lamp. Real labradorite flashes from inside the stone, on one crystal plane, only at certain angles, and its colour zones have straight, sharp edges (GIA). It is hardness 6 to 6.5, density 2.68 to 2.72. Larvikite and Nuummite are real rocks that are not labradorite.
In short
- Labradorite is a feldspar, and its flash has a direction. The Handbook of Mineralogy sheet records it as commonly exhibits iridescence, especially on {010}, with hardness 6 to 6.5 and density 2.68 to 2.72. GIA's Gems & Gemology says the iridescence is seen on that cleavage surface and, on a flat face, only at certain angles to the light.
- The one-plane rule: real labradorite flashes on one plane, from inside the stone. Eleven of the 176 sheets in this site's reference set record iridescence in their colour field. Nine are opaque metallic minerals whose iridescence is tarnish, orthoclase may show schiller iridescence, and only labradorite ties it to a crystal plane.
- Three things to see under a lens. GIA says opaque inclusions float over labradorite's colour, so the colour always arises from inside. Its colour zones often have straight, sharp boundaries, which GIA has not seen in other iridescent feldspars. The International Gem Society adds repeated twinning and black needle-like inclusions.
- Most fake labradorite is a different real rock. GIA says the anorthoclase in larvikite is often misidentified as labradorite because of its darker bodycolour. Nuummite, an iridescent amphibolite from Greenland, looks very similar but has smaller, blade-shaped crystals. Glass can carry an iridescent coating, which the IGS calls AB glass.
- Weigh only to rule out the heavy and the light. A 20.00 g piece reads 12.54 to 12.65 g in water, only 0.08 g from quartz at its closest. Glass spans 11.30 to 15.56 g, so the scale cannot clear it. Spectrolite is labradorite: the IGS gives it as the name for cut Finnish stones.
| Check | Labradorite | Larvikite (anorthoclase) | Nuummite | Coated glass | What it separates |
|---|---|---|---|---|---|
| 1. Tilt a flat face under one lamp | Flash at certain angles only; wider on a cabochon (GIA) | Iridescent feldspar; directional, as GIA says of all iridescent feldspars | Iridescent, golden yellow to violet-blue (GIA) | Coating on the surface (IGS) | Coated glass, with step 2 |
| 2. 10x lens: where the colour sits | Inside: inclusions float over it (GIA) | Shallow beneath the surface (GIA) | In elongated blades (GIA) | A surface layer; bubbles and swirls in the glass (IGS) | Glass: yes |
| 3. 10x lens: shape of the colour zones | Straight, sharp boundaries (GIA) | Straight, sharp zones not observed in other iridescent feldspars (GIA) | Some show zoning (GIA) | No zones | Labradorite against other feldspars |
| 4. Grain size across a slab or bead | Sheet: crystals to 4 cm; GIA: iridescent crystals sometimes several decimetres | A rock (GIA: anorthoclase in larvikite) | Smaller crystals, elongated blades (GIA) | No grains | Nuummite, weakly |
| 5. Weigh in water, 20.00 g | 12.54 to 12.65 g (D 2.68 to 2.72) | No sheet in the set | No sheet in the set | 11.30 to 15.56 g | Not decisive |
| 6. Refractometer | 1.560 to 1.572 (IGS) | - | - | One reading, 1.470 to 1.700 (IGS) | Glass: yes |
| 7. Hardness, rough only | 6 to 6.5 | - | - | 5 to 6 (IGS) | Weakly |
How to tell if labradorite is real: five checks, in order
Use one lamp, a 10x lens and, if you need it, a scale. Labradorite gives itself away by how its colour moves. Labradorite is a calcium-rich plagioclase feldspar; GIA defines it as plagioclase between An50 and An70. The Handbook of Mineralogy sheet for labradorite gives hardness 6 to 6.5, measured density 2.68 to 2.72, and perfect cleavage on {001}, less perfect on {010}, read from the rendered sheet.
- Tilt it under one light. On a flat face the flash appears over a narrow range of angles and then goes; on a cabochon it shows over a wider angle. GIA explains that this is why iridescent feldspars are so often cut as cabochons.
- Find where the colour sits. Under 10x, dark inclusions in real labradorite sit in front of the colour; GIA's conclusion is that the colour always arises from inside the crystal.
- Look at the edges of the colour zones. Straight, sharp boundaries between blue, green and gold zones are the labradorite signature in GIA's account.
- Check the grain. A slab made of many separately flashing grains is a rock; the International Gem Society describes dark igneous building stone in which labradorite grains flash out at many different angles. Larvikite and Nuummite fall here, and so does labradorite-bearing anorthosite, which GIA notes is used for countertops.
- Weigh it, if loose. Expect 12.54 to 12.65 g in water for a 20.00 g piece. The method is on how to measure specific gravity at home.
Finish state: labradorite; a rock containing labradorite; a different iridescent rock; or glass. Most beads and palm stones stop at step 2. Separating labradorite from moonstone is a separate question, with its own rule, on is labradorite a moonstone. The identification pages are indexed at the collecting guides.
Is my labradorite real? The one-plane rule, counted
The one-plane rule: labradorite's flash belongs to one crystal plane, so it switches on and off as the stone turns. The Handbook sheet ties it to {010}; GIA's 2025 review says the lamellae responsible make the iridescence observable on the (010) cleavage surface. A colour that sits on the surface, or shows from every direction alike, fails the rule.
Method. The 176 sheets in this site's reference set were converted with pdftotext -layout, and each was searched by script, case-insensitively, for iridescen-, schiller, play of colour, labradoresc-, opalescen-, chatoyan- and adularescen-. Twelve sheets match; eleven record iridescence in the colour field. Nine are opaque, metallic-lustre minerals whose iridescence is tarnish or surface colour: bornite, chalcopyrite, covellite, hematite, marcasite, pyrite, pyrrhotite, skutterudite and stibnite. Orthoclase may exhibit opalescence or schiller iridescence. Albite matches only on may be chatoyant. Labradorite is the only sheet that ties its iridescence to a crystal plane.
Where the rule needs help: larvikite's anorthoclase is also an iridescent feldspar, and its flash is directional too. The second and third checks, colour inside the stone and straight-edged zones, carry the weight there. Feldspar identification in hand specimen is on how to identify feldspar.
What does fake labradorite look like?
Most labradorite that is not labradorite is another natural rock, not a manufactured fake. GIA's Gems & Gemology review names two. The anorthoclase in larvikite from Norway is often misidentified as labradorite due to its darker bodycolor. Nuummite, a trade name for iridescent amphibolite first found near Nuuk, Greenland, appears very similar to labradorite but has smaller crystals and elongated blade shapes. Both are real minerals in real rock; neither is labradorite.
Glass is the manufactured case. The International Gem Society describes glass with an iridescent coating, AB glass, and opalite, a glass used to imitate moonstone or opal. Glass usually shows swirl marks and round bubbles under a lens, and a coating is a surface layer, not colour from inside. None of the sources fetched for this page describes a synthetic labradorite, so none is claimed here.
Some names that sound like fakes are real. The IGS gives spectrolite as the name for cut Finnish labradorite with very intense schiller, and GIA describes Finnish spectrolite as having a nearly black bodycolour. Rainbow moonstone is labradorite too, as the moonstone page sets out. Painted labradorite exists as an art form: GIA's feature describes an artist using the flash as a stone is tilted against a light source. Paint sits on the surface, and the lens finds it. Nothing on this site is offered for sale; the wanted list is the only commercial route.
Can you weigh labradorite to prove it is real?
Only to rule out the far-off cases, because labradorite sits 0.08 g from quartz on a 20 g piece. At the sheet's 2.68 to 2.72, a 20.00 g piece reads 12.54 to 12.65 g suspended in water; quartz reads 12.45 g. The International Gem Society's 2.69 to 2.72 gives 12.57 to 12.65 g. These figures match the moonstone page exactly.
Glass spans the whole bracket. At the gem society's 2.30 to 4.50, glass reads 11.30 to 15.56 g. A reading of 12.6 g says the piece is not dense lead glass or a heavy mineral; it does not say labradorite. The refractometer does better: labradorite reads 1.560 to 1.572 on the gem society's figures, and the sheet prints alpha 1.555 to 1.565 and gamma 1.563 to 1.573. Glass gives one reading.
Hardness is a weak test here. Labradorite is 6 to 6.5 and glass 5 to 6, so the two ranges touch at 6. The IGS notes a steel file scratches feldspar. A labradorite that has lost its flash is on why is my labradorite turning black.