Why is my labradorite turning black
Labradorite flashes only at certain angles to the light, and some has a near-black body colour. At hardness 6 to 6.5, dust wears it. Six causes, with tests.
Why is my labradorite turning black? Usually the flash is out of view, not gone. GIA says its iridescence shows only at certain angles to the light, and the IGS lists black among its body colours. A film, or a polish dulled by dust (quartz, hardness 7, against labradorite's 6 to 6.5), hides it too.
In short
- Most black labradorite is the body colour showing. GIA's Gems & Gemology says that on a flat surface labradorite's iridescence can be seen only at certain angles to the illumination. Away from that angle you see the stone's own colour, and the International Gem Society lists black among labradorite's body colours.
- The lamp, wipe and lens sequence decides which cause it is. Tilt it under one lamp: if the flash returns, nothing changed but the light. If it returns only after a wipe, it was a film. If it stays weak and a 10x lens shows fine scratches, the polish has worn.
- Wear has a number. The IGS says dust can scratch gems softer than quartz, Mohs 7, because quartz is a major component of dust. Labradorite is 6 to 6.5, half a point to a point softer. Of the 168 sheets in this site's reference set that print a hardness, 156 top out below 7.
- Some labradorite was always nearly black. GIA says the body colour is set mainly by the density of iron oxide inclusions, and describes Finnish spectrolite as nearly black, with its iridescence at the surface. The Handbook sheet's colour line does not include black; the gem references do.
- No mechanism for darkening is claimed here. None of the sources fetched for this page documents labradorite changing colour on a shelf or against skin. The causes below are what hides the flash, in order of what we judge most common. No cleaning or oiling recipe is given.
| What you see | Likely cause | The number behind it | Test that separates it | What to do next |
|---|---|---|---|---|
| Black or grey indoors, flash seen before in sun or shop light | The flash is out of view: angle and lighting | GIA: on a flat face, seen only at certain angles to the light | One lamp, tilt slowly through every angle; the flash returns | Nothing; display it under a single directed light |
| Flash on one face only; the other faces always dark | The flash plane is {010}; other faces show body colour | Sheet: iridescence especially on {010} | Only one orientation flashes; turn the stone to find it | Nothing; that is the crystal |
| A grey, greasy or cloudy film; flash weaker everywhere | Skin oil, dust or residue on the polish (our judgement) | Density and hardness unchanged: it is not the mineral | Flash brightens after a damp cloth on a hidden spot | The cleaning guide; no recipe here |
| Hazy, dull polish; fine scratches under 10x | Abrasion: the polish has worn | Hardness 6 to 6.5 against quartz dust at 7 (IGS) | Scratches under a lens, densest on high points | Repolishing is lapidary work |
| A dark line or plane through the stone that flashes differently | A cleavage crack | Perfect on {001}, less perfect on {010}, at 90 degrees | A straight line that catches the light (our judgement) | Keep it from knocks; see the break FAQ |
| Always very dark, flash bright but shallow | Near-black body colour, as in Finnish spectrolite | GIA: body colour set mainly by iron oxide inclusions | Old photographs or the label show the same | Nothing; that is the material |
| Many small grains flashing separately, or colour on the surface | Not labradorite: larvikite, Nuummite or coated glass | GIA names larvikite and Nuummite as look-alikes | The checks on the real-labradorite page | Relabel it |
Why is my labradorite turning black? The flash is directional
Labradorite's colour flash comes from one direction, so a stone seen from anywhere else shows its body colour, and that can be black. GIA's 2025 review in Gems & Gemology explains that a face near-parallel to the internal lamellae must be well polished, and that on a flat surface the iridescence can be seen only at certain angles to the illumination. A curved cabochon spreads it over a wider angle. The Handbook of Mineralogy sheet for labradorite records the effect as commonly exhibits iridescence, especially on {010}.
The lamp, wipe and lens sequence, stated once. First, put the stone under a single lamp and tilt it slowly. If the flash returns, nothing has changed but the light; diffuse room light is the commonest reason a labradorite looks dead, in our judgement. Second, if it does not return, wipe a hidden spot with a damp cloth and tilt again. Third, if the flash is still weak, look at the surface with a 10x lens. That order runs from free to diagnostic and touches the stone least.
Grey, not black, has the same causes, in our judgement. The sheet's colour line opens with gray, and the International Gem Society lists colourless, yellow, gray, black, brown, greenish and blue body colours. Which one a stone shows between flashes depends on the material, not on age.
Can dust and wear dull labradorite? Hardness 6 to 6.5 against 7
Yes: the International Gem Society says dust alone can scratch gems softer than quartz, Mohs 7, because quartz is a major component of dust, and labradorite is 6 to 6.5. That is a gap of half a Mohs point to a full point, and handling adds to it. A worn polish scatters light that a fresh polish would reflect, and GIA's requirement that the flash face be well polished is why that matters.
Counted across this site's reference set: 168 of the 176 sheets print a numeric hardness, read by script from pdftotext -layout text, and 156 of the 168 top out below 7, so dust-scale wear is the normal case, not a labradorite weakness. Thirteen sit wholly in labradorite's band of 6 to below 7, including the five other feldspars in the set: albite, anorthite, microcline, orthoclase and sanidine. The IGS rates labradorite's wearability as poor and its cleavage as always worth minding.
How to see wear, in our judgement: under a 10x lens, fine scratches crowd the high points of a cabochon or the edges of a palm stone and thin out in the hollows. Repolishing is lapidary work and is not described here. How to test hardness without marking a good face is on how to test mineral hardness properly.
Is black labradorite real? Body colour and look-alikes
Some genuine labradorite is nearly black throughout. GIA's review says the body colour of iridescent labradorite is mainly determined by the density of iron oxide inclusions, and that Finnish spectrolite has a nearly black body colour with its iridescence at the surface. A stone that was always very dark has not turned black; check old photographs or the label.
A dark stone with a flash may also not be labradorite. GIA says the anorthoclase in larvikite is often misidentified as labradorite because of its darker body colour, and that Nuummite, an iridescent amphibolite, appears very similar. The checks, the one-plane rule and colour inside the stone, are on how to tell if labradorite is real, and the moonstone question on is labradorite a moonstone.
What this page does not say: it gives no mechanism by which labradorite darkens, and no oiling, charging or cleaning recipe, because no fetched source documents one. General cleaning is on how to clean mineral specimens. The damage and diagnosis pages are indexed at the collecting guides. Nothing on this site is offered for sale; the wanted list is the only commercial route.