Matrix Opal: When the Fire Stays in the Rock
Opal knowledge · Opal types
When the fire stays in the rock
Matrix opal is the opal type in which stone and host rock cannot be separated. The play of colour does not sit on top as a closed layer but runs through the mother rock as a network of fine veins and dots. The result looks like a starry sky in stone and can be told apart from any other opal at first glance.
What this is about: Matrix opal is genuine opal material finely distributed within the host rock. It is not an inferior opal and not a fake, but a form of its own. Worth knowing: part of the material on the market is treated, and that must be disclosed at the point of sale.
What is a matrix opal?
In most opals the silica gathered in one connected cavity, which is why a closed opal layer forms. With matrix opal it went differently: the solution seeped into the fine pores and cracks of the surrounding rock and solidified there. So the opal is not on the stone, it is in the stone.
The best known deposits lie in Andamooka in South Australia and in parts of Queensland. Where exactly a stone comes from and what sets the regions apart is covered in Where opals come from.
How does it differ from boulder opal and solid opal?
All three contain genuine opal material, but they are built differently. This is where confusion arises most often.
| Type | Structure | How to recognise it |
|---|---|---|
| Solid opal | opal throughout | even colour surface, no foreign material |
| Boulder opal | closed opal layer on ironstone | clear dividing line between stone and host rock |
| Matrix opal | opal finely spread through the rock | colour in dots and veins, no dividing line |
| Doublet | glued layers | dead straight glue line along the edge |
Telling it apart from glued goods matters: matrix opal is naturally grown, a doublet is assembled. How you tell the difference is covered in Doublet and triplet.
What does it mean when a matrix opal is treated?
What you should know before buying
A considerable share of the matrix opal on the market, especially from Andamooka, is blackened: the porous rock is soaked in a sugar solution and treated with acid so that carbon is deposited in the pores. The base turns dark and the play of colour stands out far more clearly as a result.
This is an accepted method and not a fake. But it is subject to disclosure: anyone buying matrix opal should be told explicitly whether the stone has been treated. If the question is answered evasively, treat that as a warning sign.
The same principle applies as with any opal purchase: what counts is not the claim but the proof. More on this in How to spot a real opal.
What is a matrix opal worth?
Matrix opal usually sits below solid opal and boulder opal of comparable colour strength. The reason is not the quality of the opal itself but the proportion: a matrix stone contains less opal material than a solid opal of the same size.
Raises the price
Dense, evenly spread play of colour across the whole surface, strong colours, untreated.
Lowers the price
Only scattered dots of colour, large colourless areas, vague information about treatment.
How opal prices come about in general is covered in How much is an opal worth.
We mainly carry solid opals with a closed play of colour. If the subject of rock and origin appeals to you, take a look at boulder opal , where the mother rock stays visible. The full range is under Opal jewellery.
What to look out for when buying
With matrix opal, always ask whether the stone has been treated. Sugar and acid blackening is common in the trade and no flaw in itself, but it has to be stated. If someone offers you a deep black matrix opal at the price of an untreated stone and dodges the question, walk away. Ask before you buy if in doubt.
Common questions about matrix opal
What is a matrix opal?
An opal type in which the opal material sits finely distributed in the pores and cracks of the host rock instead of forming a closed layer. The play of colour appears as a network of dots and veins.
Is matrix opal a real opal?
Yes. The opal material has grown naturally.
What is the difference to boulder opal?
With boulder opal a closed opal layer sits on the ironstone, with a visible dividing line. With matrix opal the opal runs through the rock itself and there is no dividing line.
Is matrix opal treated?
A considerable share is, especially from Andamooka. The porous rock is blackened with sugar and acid so the play of colour stands out more strongly.
Is matrix opal suitable for everyday wear?
Thanks to the high proportion of rock it is often sturdier than a free standing solid opal. Treated stones should still be kept away from strong heat and solvents.
Can you wear matrix opal every day?
Yes, even better than many solid opals. The mother rock supports the stone and makes it less sensitive to knocks.
If you are unsure or have questions, you are welcome to contact us at any time, even if you did not buy the opal from us. Contact form, email cs@libertyangels.de or call +49 171 1603048.
Verified authenticity
by Liberty Angels
Only natural, genuine opals. Each certificate is linked online to your order, so it is tamper-proof.
Written by Anton Kehler
Gründer FAERELLI & Liberty Angels
