At first glance, labradorite can be surprisingly quiet.
It might look smoky grey, greenish or almost charcoal. Then you turn it towards the light and, suddenly, a streak of brilliant blue appears across the surface.
Move it again and it disappears.
This strange shifting colour is one of the reasons labradorite is such a fascinating gemstone. It can look completely different from one moment to the next — and, unlike a blue gemstone such as sapphire or aquamarine, that flash of colour isn't simply the colour of the stone itself.
There is something much more interesting happening inside.
The blue has a name: labradorescence
The optical phenomenon responsible for labradorite's flashes of colour is known as labradorescence.
Labradorite belongs to the feldspar family of minerals. Inside certain pieces of labradorite are incredibly fine layers with slightly different compositions. These microscopic structures interact with incoming light, causing particular wavelengths of light to be reflected back towards our eyes.
The result can be intense flashes of blue, green, gold, orange and occasionally other colours.
Gemologists describe labradorescence as an iridescent optical effect created by light interacting with these extremely thin internal layers.
So although it can look as though there is a layer of blue sitting beneath the surface, the colour you're seeing is really the result of light meeting structure.
And that is why it can vanish just as quickly as it appears.
Why does labradorite change when you move it?
This is perhaps the loveliest part.
Labradorescence is directional.
The internal layers responsible for the effect are arranged in particular orientations within the crystal. As the position of the stone, the light source or your eye changes, the way light interacts with those layers changes too.
That's why you can hold a piece of labradorite perfectly still and see very little, then tilt it by a few degrees and suddenly find a vivid streak of blue.
It also explains something anyone who has tried to photograph labradorite will recognise:
the camera doesn't always see what you can see.
A stone that looks spectacular as you turn it in your hand can appear much quieter in a photograph taken from one fixed angle.
In a way, labradorite isn't really a gemstone designed to be seen in a still image.
It needs movement.
But why is the flash so often blue?
Not every piece of labradorite flashes blue. Green, yellow, gold, orange and more varied iridescent colours can occur too.
The colours depend in part on the dimensions and optical properties of the microscopic layers inside the feldspar. Research into iridescent labradorite has shown that different layer thicknesses correspond with different colours of reflected light.
Blue happens to be one of the colours particularly associated with labradorescence, and perhaps the most recognisable.
Against the stone's naturally smoky background, that sudden electric blue can look almost illuminated from within.
But nothing has been added to make it glow.
It's simply light revealing a structure far too small for us to see.
A tiny landscape hidden inside a gemstone
Look closely at natural labradorite and you'll also notice that it isn't perfectly uniform.
One area may appear dark grey. Another might have a mossy green cast. Fine lines, cloudy areas and subtle variations can run through the stone.
Then there is the flash itself.
One piece might produce a broad blue glow, while another reveals only a narrow streak when it reaches exactly the right angle.
That variation is part of natural labradorite rather than something to be corrected.
Two stones cut to exactly the same shape and size can still behave very differently in the light.
For jewellery, that means something rather wonderful:
no two pieces ever reveal themselves in quite the same way.
Is labradorescence the same as moonstone's glow?
They're related, but they aren't quite the same phenomenon.
Moonstone is another member of the feldspar family. Its characteristic soft, floating sheen is generally called adularescence, whereas the stronger iridescent flash associated with labradorite is called labradorescence. Gemologists distinguish between the two according to the feldspar and the structures producing the optical effect.
Visually, they can feel very different too.
Moonstone often seems to hold a soft pool of light.
Labradorite can feel much more sudden.
Grey.
Grey.
Grey.
And then... blue.
Why are labradorite gemstones often smoothly polished?
There is another piece of science hidden in the shape of the jewellery.
Gemstones displaying optical phenomena are often cut and polished in ways that help us see those effects. GIA notes that curved surfaces can allow iridescence in feldspars to be visible over a wider range of angles, which helps explain the use of smooth cabochon-style cuts rather than relying only on conventional facets.
A polished surface also lets light enter the stone cleanly enough for its internal structure to become the star of the show.
With labradorite, the most interesting thing isn't necessarily the cut.
It's what happens underneath it.
Why every labradorite necklace looks slightly different
This is particularly important when choosing natural labradorite jewellery online.
The colour and pattern you see in one stone cannot be replicated perfectly in another.
Your piece might have a strong blue flash. Another may lean towards green and gold. Some appear darker; others more translucent. Even the position of the flash can vary.
And because labradorescence depends on angle and illumination, your stone will change throughout the day too.
Soft window light may reveal something different from bright sunshine. A flash visible while the pendant is moving may disappear when it hangs completely still.
It isn't a flaw or inconsistency.
It's simply what natural labradorite does.
A stone that rewards a second look
Perhaps that's why labradorite works so beautifully as a small piece of jewellery.
From across the room, it doesn't necessarily demand attention.
You have to get closer.
You have to move it.
You have to notice.
Our Sterling Silver Labradorite Crescent Moon Necklace uses a tiny 12 mm piece of natural labradorite set into a polished silver crescent. Every stone has its own markings and flashes of colour, so each little moon is slightly different.
The pairing feels particularly fitting: a gemstone whose appearance changes with the light, shaped into a moon, something we have watched apparently change in the sky for thousands of years.
Sometimes the most interesting things are the ones that don't reveal everything at first glance.
A tiny moon. A hidden flash of blue. And a little piece of mineral science you can wear.
A Little Labradorite to Keep Close
There's something lovely about a gemstone that reveals a different side of itself as the light changes.
Our sterling silver labradorite necklaces celebrate that natural beauty, from a delicate heart pendant to a tiny crescent moon. Each stone has its own markings and flashes of colour, making every piece a little different.