Born of Water, Time and Silence
How opals form is above all a story of patience: the finished stone you hold in your hand took shape over spans of time our imagination simply cannot hold. Those long ages also decide why some stones glow and others stay milky.
No two opals are alike, and that starts at birth. Some grow in the Australian desert, some in volcanic rock in Ethiopia, some where a piece of wood or a shell lay in the distant past. We will walk the whole way with you, from a single drop of water to the finished play of color on your hand.
What is an opal actually made of?
An opal is solidified silica gel: amorphous silicon dioxide with water locked inside, chemically SiO₂·nH₂O. “Amorphous” is the key word here. Unlike quartz, sapphire or diamond, an opal has no ordered crystal lattice. At heart it is a gel that grew ancient, and that is exactly what makes it so singular.
How does an opal form, step by step?
Millions of years pass between the first drop of water and the finished stone. The path runs through five stages, and with each one the stone that no one will ever find twice comes a little closer.
Water takes up silica
Over long stretches of time, rain seeps through soils and rock rich in silicon dioxide and dissolves silica out of them. What remains is a thin, mineral-rich solution that slowly travels downward.
The solution gathers in cavities
It works its way into cracks, fissures and crevices, often ones opened up by tectonic movement, weathering rock or decaying fossils. There it comes to rest.
The water evaporates
Over long dry phases the water escapes bit by bit. What stays behind is a soft silica gel that fills the cavity completely, the raw material of the later stone.
The spheres fall into order
Tiny spheres of silicon dioxide form inside the gel. If they are all the same size and stack into a regular lattice, the foundation for the play of color is laid. If that order never comes, the result is a quiet, milky opal.
Over millions of years the stone solidifies
Under pressure the gel hardens very slowly into solid opal. Just how slowly can only be estimated: the great Australian deposits sit in rock from a Cretaceous inland sea, more than a hundred million years old. Some sources reckon on millions of years for just a few centimeters. The stone on your hand is older than the dinosaurs.
Why do opals shimmer in every color?
The play of color does not come from pigments but from pure light. The tiny silica spheres sit in a regular lattice and act like a natural diffraction grating: they split incoming white light into its spectral colors, much like a rainbow or the back of a CD.
The decisive point: which color you see depends on the size of the spheres. Small spheres, around 150 nanometers, diffract short-wavelength light and show blue and violet. Large spheres, around 350 nanometers, diffract long-wavelength light and show orange and red. That is exactly why red fire in an opal is so rare and so sought after: it takes the largest, perfectly ordered spheres.
And this is where precious opal parts ways with common opal. If the spheres lie in order, the shimmering play of color appears. If they vary in size and scatter chaotically, the stone stays milky and quiet. Both are genuine opal; nature simply stacked more neatly one time than the other.
| Sphere size | Visible color | Frequency |
|---|---|---|
| small (~150 nm) | Blue, violet | most common |
| medium (~250 nm) | Green, turquoise | common |
| large (~350 nm) | Orange, red | rarest |
Which color reveals which structure?
Tap a color.
Do all opals form the same way?
No. Opal can form in four very different ways, and the path shapes the finished stone, from color to transparency to origin. That is why an Australian black opal and an Ethiopian Welo opal feel so different, even though both are called “opal”.
1 · Sedimentary
The most common path. Water dissolves silica out of sandstone, seeps into cavities and evaporates over geological spans of time. This is how most of the Australian deposits formed, among them white opal, crystal opal and the coveted black opal.
2 · Volcanic
Silica-rich water fills cavities in volcanic rock such as rhyolite or tuff. This is how the Ethiopian Welo opals with their vivid colors come about, along with the orange-red fire opals from Mexico.
3 · Organic (petrification)
Here silica replaces organic material piece by piece. This is how wood opal and opalized fossils form, and at Lightning Ridge even opalized shells and dinosaur bones.
4 · Boulder
In Queensland, opal fills fine cracks in ironstone nodules. The dark host rock stays with the stone as its backing, and that is what makes a boulder opal.
Each of these ways of forming brings forth its own opal types, from black opal and the Ethiopian Welo opal to boulder opal and fire opal. You will find an overview of all opal types in the lexicon.
Around 95 percent of the world’s precious opal comes from Australia. We cover fire opal and boulder opal here as background, because they belong to the family. In the Liberty Angels range you will mainly find Australian and Ethiopian precious opal.
Naturally grown or made in a lab?
Synthetic opals have been around since the 1970s, modeled on the natural sphere structure and produced in weeks instead of millions of years. On top of that come pure imitations made of plastic or glass. Neither is “fake” in the sense of worthless, but neither grew in the earth. Here is how to tell grown from made:
Naturally grown
over millions of years in the earth
- irregular, living play of color that shifts as the angle changes
- fine inclusions and small natural marks
- cool on the skin, feels “stony”
- every piece is one of a kind
Lab & imitation
produced in weeks or merely imitated
- often too regular a pattern, sometimes a columnar or snakeskin effect
- strikingly flawless, without a single natural trace
- plastic feels warm and light
- many stones look identical
You can read the detailed guide with every last sign here: How to identify a real opal: the 5 most reliable signs.
Your GSB certificate: real opal, in black and white
When a stone has taken millions of years, you should be able to be sure of it. Every piece of Liberty Angels jewelry is GSB-certified: real, naturally grown opal, set in 925 silver or 14K or 18K gold. The certificate is assigned online directly to your order, which makes it forgery-proof and part of your piece.
Find your opal
Handcrafted, GSB-certified, in silver and gold. Every stone out of the depths of time.
Opal necklaces
Pendants that catch the light.
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Opal rings
Your play of color for every day.
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Opal earrings
A sparkle that goes with you.
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Opal bracelets
Play of color around your wrist.
Discover →Common questions about opal formation
How are opals formed?
Opals form when silica-rich water seeps into cavities in rock, evaporates and leaves tiny spheres of silicon dioxide behind. Over millions of years these harden into solid opal.
How long does it take for an opal to form?
Millions of years. The Australian deposits sit in rock more than a hundred million years old. By current estimates, even a few centimeters of opal take millions of years.
What is an opal made of?
Of amorphous silicon dioxide with water locked inside (SiO₂·nH₂O). The water content is usually between 3 and 21 percent. Opal has no crystal lattice and, at Mohs 5.5 to 6.5, is relatively soft.
Why do opals have a play of color?
Tiny spheres of equal size lie in a regular lattice and bend the light like a rainbow. The size of the spheres decides the color: small for blue, large for red.
Where do most opals form?
Around 95 percent of precious opal comes from Australia. Other important sources are Ethiopia for Welo opals and Mexico for fire opals.
Can opals be made artificially?
Yes. Since the 1970s there have been synthetic opals that reproduce the sphere structure. They are made in weeks instead of millions of years. Alongside them there are pure imitations of plastic or glass.
How does wood opal form?
Through petrification: silica gradually replaces the organic material of wood or other fossils until an opalized image of it remains.
Last updated: July 2026.
