Buying Opal in Coober Pedy: A Buyer's Guide

Know What You're Buying

Before you hand over your card, ask the retailer to describe the stone in plain language — and get that description in writing. It only takes a moment, and it's the single best protection you have.

Australian Consumer Law requires gemstone descriptions to be truthful. The ACCC has specifically warned that businesses should properly disclose synthetic, imitation and treated gemstones, and should never represent an artificial product as natural.

Source: ACCC — fair trading in the jewellery industry

Understanding the Different Types of Opal

Natural solid opal

A natural solid opal is naturally formed and presented as one piece — it hasn't been assembled from separate layers. Natural opal is often described by its body tone and appearance, including:

Light or white opal
Dark opal
Black opal
Crystal opal
Boulder opal
Matrix opal

These descriptions don't automatically tell you the stone's origin or value — they're about appearance.

Rough opal

Rough opal is opal as it came out of the ground — uncut and unpolished. It can be sold either way: rough, or cut and polished into a cabochon or shaped stone. Being unpolished doesn't change whether the opal is natural, and a reputable retailer will tell you plainly whether you're looking at rough or polished material.

Boulder opal

Boulder opal is natural opal still attached to the host rock it formed in. It's predominantly mined in Queensland, not the Coober Pedy field, so a Coober Pedy or South Australian origin shouldn't be assumed just because a piece is described as boulder opal. That backing is a natural part of the specimen, not an artificial layer glued on — so boulder opal should never be confused with a doublet.

Matrix opal

Matrix opal forms when natural opal is distributed through pores or spaces within its natural host rock. Some matrix opal is treated to darken the host material and make the colour more visible — any such treatment should be disclosed to you.

Opal doublet

A doublet is an assembled stone made from two pieces:

A thin layer of natural opal
A separate backing material the opal has been attached to

A doublet does contain natural opal, but it isn't a natural solid opal, and it should be clearly sold as an opal doublet — not just "an opal."

In Coober Pedy, doublets are often backed with boulder opal for extra strength. That's a legitimate technique — it makes for a sturdier stone — but it's still a doublet, not a natural solid opal or a boulder opal in its own right, and should be described that way.

Opal triplet

A triplet is an assembled stone made from three layers:

A dark backing
A very thin layer of natural opal
A clear protective dome, commonly glass, quartz or another transparent material

A triplet should be clearly described as an opal triplet, not simply as an opal or a solid opal.

Mosaic or chip opal

Mosaic products are assembled from small pieces or chips of opal, usually arranged on a backing and held together or covered with resin. They may contain genuine natural opal, but the finished item is a manufactured composite and should be disclosed as such.

Opal inlay

Opal inlay is a jewellery-making technique in which thin, carefully shaped pieces of opal are fitted and secured directly into recessed channels or spaces in a jewellery setting. The opal generally sits flush with the surrounding metal, and may form a continuous line, geometric pattern or decorative design.

An inlay may contain:

One continuous piece of opal
Several individually shaped pieces fitted closely together
Natural, synthetic or imitation opal
Opal attached with adhesive, almost always over a black backing painted underneath to bring out the colour

That black backing is a treatment, not a natural part of the stone. So although the opal used in an inlay may well be natural, the finished piece is enhanced in much the same way a doublet is — it is not a solid opal, and shouldn't be described as one.

Unlike a doublet or triplet, an inlay is normally constructed as part of the jewellery setting rather than sold as a separate layered gemstone. It differs from mosaic or chip opal because the pieces are deliberately cut and fitted into defined channels, instead of being mixed or arranged within a resin tile.

Inlay containing natural opal can be attractive and valuable, but it should not be described in a way that implies the item contains one natural solid opal. Any synthetic material, imitation material, backing, colouring, resin, paint or other treatment should be disclosed.

Everyday wear: because the opal sits flush in a channel over a painted backing rather than as one solid stone, inlay jewellery is generally more delicate than a solid opal setting. An inlay ring in particular is usually not meant to be worn all the time — ask the retailer for their care advice for the specific piece.

Treated opal

Treated opal is natural opal, or opal-bearing material, whose appearance has been altered by a process such as:

Smoke treatment
Sugar-and-acid treatment
Dyeing
Oil, wax or resin impregnation
Surface coating
Fracture filling
Other colour or clarity enhancement

Treatment doesn't necessarily make a stone unattractive, but it can affect its value, durability and care requirements. It should be disclosed before you buy, and recorded in writing.

Synthetic opal

Synthetic opal is made through a laboratory or industrial process. It may share much of natural opal's chemical composition and physical structure, but it didn't form underground — and it must never be represented as natural opal.

Terms like these should prompt further questions:

Synthetic opal
Laboratory-created opal
Lab-grown opal
Created opal

Simply ask the retailer to state clearly whether the opal is natural or manufactured.

Imitation opal

Imitation or simulated opal is made to resemble opal without sharing its chemical composition and physical structure. Imitations can be made from glass, plastic, resin or other materials, and should never be represented as natural or synthetic opal.

Source: Opal Association — Opal Industry Nomenclature (developed by the Gemmological Association of Australia)

Can You Identify Opal Yourself?

Some products have visible clues, but appearance alone isn't always reliable.

Possible signs of a doublet

Viewed from the side, a doublet may show:

A straight join between the opal and its backing
A dark backing that looks different from the upper opal layer
Glue, or a very even boundary between the layers
A closed metal back on the setting, hiding the underside of the stone entirely

A setting can conceal this join entirely — a closed back is a common way retailers (or previous owners) do this, and is generally worth asking about.

Possible signs of a triplet

A triplet may show:

Three separate layers when viewed from the side
A clear domed top
Colour that appears magnified beneath the dome
A very thin layer of natural opal between the cap and backing
A closed metal back on the setting, hiding the layers underneath

Possible signs of synthetic or imitation material

Some manufactured products may show:

An unusually regular or repeating pattern
Colour patterns that look identical from one item to another
Perfectly uniform material across a large number of stones
Column-like patterns when viewed from the side
A plastic, resinous or glass-like appearance

These are warning signs, not proof. Modern synthetic and imitation materials can be difficult to identify, particularly once mounted in jewellery.

Please don't scratch, heat, immerse or chemically test a retailer's opal. Reliable identification may require a qualified gemmologist and specialist equipment. The Gemmological Association of Australia offers advanced training specifically covering natural opal, composites, treatments, synthetic opal and imitations.

Source: Gemmological Association of Australia — Advanced Opal Course

Questions to Ask Before Buying

Is this natural opal?
Is it a natural solid, boulder opal, matrix opal, doublet, triplet, mosaic, synthetic or imitation?
Has the opal been treated, enhanced, dyed, smoked, coated, filled or impregnated with resin?
Is every part of the stone natural opal?
Is a backing or transparent cap attached to it?
Where was the opal mined?
What evidence supports the claimed origin?
Was the opal cut locally, or only set into jewellery locally?
What metal is used in the setting?
Is the metal solid gold or silver, plated, or another alloy?
Does the item require any special care?
What is the store's return policy if an independent examination finds the description incorrect?
Will you provide a written certificate recording exactly what the stone is and how much I paid?

A reputable retailer should be happy to answer reasonable questions like these in plain, understandable language.

Questions to ask about inlay jewellery

Is the inlay made from natural opal?
Is every coloured section natural opal?
Is it made from one piece or several separate pieces?
Has synthetic or imitation opal been used anywhere?
Has the opal or its backing been painted, dyed or otherwise treated?
What adhesive or resin has been used?
Can damaged inlay sections be repaired or replaced?
Will the construction and materials be recorded on the certificate?

Ask for a Written Certificate

Before paying for a significant opal purchase, ask for a certificate or written sales description covering:

Retailer's legal or registered business name
ABN
Store address and contact details
Date of purchase
Receipt or certificate number
Clear photograph or identifying description of the item
Whether the stone is natural, composite, treated, synthetic or imitation
Whether it's a solid, boulder, matrix, doublet, triplet or mosaic product
Any known treatment or enhancement
Claimed geographic origin — and the basis for that claim
Metal type and purity where the opal is set in jewellery
Total amount paid
Any applicable valuation amount, clearly separated from the purchase price
Care instructions
Return or remedy information
Retailer's name and signature

The certificate should state the actual amount you paid — not merely an estimated replacement value or a claimed retail value.

Important distinction: a document issued by the retailer records what the retailer has represented and what you paid. It is not automatically an independent gemmological report or valuation. For a high-value purchase, consider asking for an independent gemmological identification report, an independent valuation, and confirmation that the assessor has no financial interest in the sale. The stone described in an independent report should be clearly linked to your item by a photograph, dimensions, weight, setting description or identifying number.

Purchase Price Versus Valuation

These are not necessarily the same thing:

Purchase price: what you actually paid.
Valuation or replacement value: an opinion about the amount required to replace the item.
Asking or ticket price: the price advertised before any discount.

A large valuation figure doesn't necessarily mean you got a bargain. It's worth asking who prepared the valuation, when it was prepared, what its purpose was, and whether the valuer was independent of the seller.

Increase in Value

A salesperson can tell you about the stone in front of you, but they cannot give you financial advice. Under Australian law, financial advice must be provided by a registered financial adviser — so a claim that an opal is a good "investment," or is guaranteed to increase in value, isn't something a retail salesperson is licensed to make.

You're buying in a retail environment. Buy opal because it makes you feel good. Buy it because it's one of the rarest gemstones in the world. Buy it because it's a colourful piece of history, formed around 120 million years ago. Buy it because it's our national gemstone — as Australian as Waltzing Matilda.

Check the Claimed Origin

"Purchased in Coober Pedy," "cut in Coober Pedy" and "mined in Coober Pedy" are three different statements. If local origin matters to you, ask:

"Was this opal mined in the Coober Pedy opal field, and will you record that origin on the certificate?"

A retailer should have a reasonable basis for making an origin claim. Under Australian Consumer Law, product-origin representations must be truthful, accurate and based on reasonable grounds.

Source: ACCC — country of origin claims

Before You Leave the Store

Take a moment to confirm that:

The description on the receipt matches what you were told
"Solid," "doublet," "triplet," "treated," "synthetic" or "imitation" is recorded where applicable
Any claimed Coober Pedy origin is written down
The amount you actually paid appears on the receipt or certificate
The certificate identifies your particular item
You understand the return policy and care instructions
You've photographed the item, receipt and certificate

If You Have Concerns

First, contact the retailer and explain the problem. Keep the item, receipt, certificate, advertisements, photographs and any written communications.

If the matter can't be resolved, consider obtaining an independent gemmological report. You can also seek guidance from your state consumer-protection agency, or report potentially misleading conduct to the ACCC.

Australian Consumer Law may entitle you to a repair, replacement, refund or compensation where a product doesn't meet applicable consumer guarantees, or was materially misrepresented.

Source: ACCC — claiming compensation

Disclaimer

This guide provides general consumer information and does not authenticate, grade or value individual opals. Visual clues are not conclusive, and reliable identification may require examination by a qualified independent gemmologist.

Inclusion of a retailer elsewhere on this website does not constitute certification or endorsement of its products.