The Opal Buyer's Handbook

The Library · Free Buyer’s Handbooks

How to judge Australia's own stone the way the trade does — body tone, brightness, pattern, and the questions that protect you.

Written by Anna Lulinkova — FGAA-Qualified Gemmologist, Ministry of Gems®

Foreword: The Stone That Plays by Different Rules

Anna, our FGAA-qualified gemmologist, on why opal humbles even experienced jewellers — and how this handbook will teach you to judge it the way the trade does.

The first opal I ever assessed professionally, I got wrong. I had trained on sapphires, where the instincts are reliable: stronger colour, cleaner stone, better cut, more carats — more value. So when a dealer laid out a broad, clean, ten-carat opal beside a five-carat stone half its size, I reached for the big one. He let me. Then he tilted the smaller stone under the light, and it flashed a broadside of red and green so vivid it made the larger stone look like wet cement. The small stone was worth several times the big one. Nothing in my sapphire training had prepared me for that.

That is opal. It is the gem that plays by different rules, and almost nobody tells the buyer what those rules are. Jewellers who can grade a diamond in their sleep will hesitate over an opal, because the four Cs — the framework the entire trade runs on — simply do not apply. Opal is valued on three things you have probably never been taught to see: body tone, brightness, and pattern. Miss any one of them and you can overpay badly, or walk past a remarkable stone without knowing it.

Why the confusion serves nobody

Opal is Australia's national gemstone, and yet the knowledge of how to judge it has stayed locked inside the trade — passed between miners at Lightning Ridge and Coober Pedy, cutters, and a small circle of dealers. Into that vacuum flow the two problems that damage buyers most: assembled stones (doublets and triplets) sold without clear disclosure at solid-opal prices, and hydrophane material — mostly from Ethiopia — that can absorb liquids, change appearance, and take dye, sold without a word about what it is.

Let me be plain about our position, because it runs through every chapter of this book: a doublet is a legitimate product. So is a treated stone. The sin is never the product; the sin is silence. A disclosed doublet at a doublet's price is an honest way to wear a beautiful face of opal for less. An undisclosed one is a quiet theft. This handbook exists so that silence stops working on you.

In opal, brightness pays the bill; everything else negotiates.

What you will be able to do

By the end of this book you will be able to do four things that most people who own opals cannot.

You will read body tone — the lightness or darkness of the stone's underlying body, judged face-up with the play-of-colour mentally set aside. It is the single biggest driver of what family a stone belongs to, and what it should cost.

You will judge brightness honestly. Brightness is where the money lives, and it must be judged in soft, indirect daylight — for us in Sydney, that means near a south-facing window; in the northern hemisphere, a north-facing one — never under a jeweller's halogen spotlight, which flatters every stone in the room. This week, try it: take any opal you own to that window, hold it at arm's length, and tilt it slowly through a full arc. What survives that test is real.

You will name patterns and know which ones carry a premium, so that the word "harlequin" on a listing makes you look harder rather than reach for your wallet.

And you will spot a doublet: the tell-tale straight, dark line at the girdle where opal meets backing, the suspiciously flat base, the reason a mounted stone with a closed back deserves extra questions. You will also know the three questions to ask every seller, of every opal, every time: Is it solid, or assembled? Is it treated in any way? Is it hydrophane material?

Where the money hides

A short preview, because it reframes everything that follows. Buyers consistently overpay for size and underpay attention to brightness. In our experience, a small, genuinely bright stone will hold your affection far longer than a large, dull one bought because it looked impressive across a counter. The places to save without regret are equally real: crystal opal often delivers extraordinary play-of-colour for less than black opal of similar fire, and a well-made, honestly disclosed doublet is a perfectly respectable way to put Lightning Ridge colour on a hand. The place never to save is certainty — knowing exactly what the stone is before money moves.

How to use this book

The chapters run in the order a purchase actually unfolds: what opal is and where it comes from, then body tone, brightness and pattern, then the assembled and treated material, then the practical business of buying. Read it straight through if you are new to the stone. Dip into single chapters if you are not. But whatever else you do, keep the checklist chapter. It compresses the whole book into the questions and observations you can carry into any showroom, opal shop or online listing. The rest of this handbook is the education; that chapter is the tool.

We wrote our Sapphire Buyer's Handbook because sapphire is the stone our family has mined and cut across three generations, back to the Ceylon gem fields of the 1960s. We wrote this one because we are an Australian house, opal is Australia's own stone, and it deserves buyers who can see it properly. You do not need to buy anything from us for this book to do its work. Our only advice on choosing, here and in every chapter that follows, is the same advice we give across a desk in Sydney: buy the stone you cannot stop looking at — once you know exactly what it is.

— Anna, FGAA Gemmologist, Ministry of Gems, Sydney

What Opal Is — and the Kinds That Matter

Opal is the one major gem the four Cs cannot describe — so before you can judge it, you need to know what it is, how Australia made it, and which of its families you are actually looking at.

The overwhelming share of opal ever dug in Australia would not hold your eye for a second. Miners call it potch: grey, amber or honey-coloured silica with no fire in it, and they shift tonnes of it for every parcel that flashes. The strange part is that potch and precious opal are chemically the same stone — hydrated silica, nothing more. The difference is architecture, on a scale no eye can see.

An accident of stacking

Precious opal is built from spheres of silica a few hundred nanometres across. Where those spheres grew to a uniform size and settled into an orderly grid, the gaps between them diffract light — white light goes in, pure spectral colour comes out. Where the spheres are jumbled or mismatched, light passes through unbothered, and you have potch. Sphere size sets the palette: smaller spheres return only blues and violets; it takes larger spheres, still perfectly ordered, to return red. That is why a stone that flashes red is scarcer than one that flashes blue — nature had to do something harder for longer.

Black opal is not black; it is a dark stage on which colour performs.

Australia holds this stage almost alone because of the Great Artesian Basin. A shallow inland sea covered much of the continent's interior in the Cretaceous. When it retreated, its sediments weathered for millions of years; groundwater dissolved silica from those sediments and carried it down into faults, seams and the voids left by shells and bone, where it slowly gelled and hardened. The great fields — Lightning Ridge, Coober Pedy, White Cliffs, Andamooka, the Queensland boulder country — all ring the margins of that vanished sea.

The families a buyer meets

Six names cover nearly everything you will be offered.

• Black opal — play-of-colour over a dark body, the classic Lightning Ridge stone and the most expensive form of opal.
• Dark opal (sometimes "semi-black") — the middle ground: body darker than grey, not quite black.
• Light and white opal — pale to milky body, Coober Pedy's staple.
• Crystal opal — transparent to translucent stone of any body tone. The name describes see-through-ness only; opal has no crystal structure at all.
• Boulder opal — Queensland opal formed in thin seams within ironstone, cut with the host rock left naturally attached.
• Matrix opal — colour dispersed through the pores of the host rock itself, as in Andamooka matrix and the Yowah nuts.

Body tone, taught properly

The trade grades an opal's background darkness on a scale from N1 to N9. Learn to use it and you will never again be at the mercy of the word "black" in a listing.

Judge face-up. Mentally switch off the play-of-colour — you are grading only the backdrop behind it. N1 is the darkness of wet ink or black glass. N4 is the lightest tone still called black. N5 and N6 are dark opal: think slate, or strong black tea. N7 to N9 are light opal, ending at N9, the white of milk. Do this in soft indirect daylight — for us in Sydney that means a south-facing window; in the northern hemisphere, north-facing.

Why does black command the premium? Contrast. The diffracted colour is the same physics in every family, but against a dark stage it reads saturated and complete, while against a white body some of it washes out. A red flash on an N1 body burns; the identical flash on N9 whispers.

Two things to do this week. First, whenever a stone is offered to you as "black", ask for its body tone as an N-number, in writing — an honest seller will give it without hesitation, and every opal we offer states it as a matter of course. Second, put a dark stone and a light stone side by side under the same window and watch what the background does to identical colour. Ten minutes of that is worth a chapter of theory.

Boulder's ironstone is not a trick

Newcomers sometimes flinch at boulder opal because it is "opal stuck to rock" — it sounds like the assembled doublets they have been warned about. The distinction matters. In a doublet, a person has glued a thin slice of opal to a dark backing. In boulder, nature did the attaching: the silica precipitated inside a crack in the ironstone a hundred million years ago, and the cutter has simply followed the natural seam. The join is undulating and irregular, the face often gently domed along the seam's own contours. It is one stone, made that way in the ground. Assembled stones get a chapter of their own later in this handbook; boulder does not belong in it.

One consequence for your wallet: boulder is properly priced per stone, not per carat — the chapter on the fields explains why.

Where the value hides

The costliest error in this corner of the market is paying black-opal money for a dark stone — an N5 or N6 described loosely as "black". The N-scale in writing is your protection. The happiest discovery runs the other way: dark opal and boulder both put colour on a dark stage at a fraction of black opal's price, and a brilliant N6 will outshine a sleepy N2 in any honest light. Brightness — the subject we take up next — can matter more than body tone, and the market has not fully priced that in. Crystal opal with strong colour is another quiet corner where knowledge beats budget.

Buy the stone you cannot stop looking at. The families and the N-scale exist so you know precisely what it is you cannot stop looking at — and what it should cost.

Play-of-Colour: Learning to Read the Fire

Opal is the only major gem you must watch rather than merely look at — here is how diffraction, the order of colours, brightness and pattern turn moving light into value.

The first thing an experienced opal buyer does in a strange room is turn most of the lights off. A dealer's office lit by six downlights makes every opal in the parcel look magnificent, because each stone has six chances to catch a beam. Under one lamp, the truth comes out. Some stones keep burning. Most go quiet.

That single habit — one light, slow rotation, patient eyes — is the whole discipline of this chapter. But it helps to know what you are actually watching.

What is happening inside the stone

Opal is not coloured the way a sapphire is coloured. There is no pigment, no chromium, no iron doing the work. Precious opal is built from millions of microscopic silica spheres, and in the valuable material those spheres are close to identical in size and stacked in an orderly grid. The gaps between them act like a diffraction grating: white light enters, is split into its spectral components, and only certain wavelengths emerge to your eye. Turn the stone, change the angle, and different wavelengths win. That is play-of-colour — not a colour the stone has, but a performance the stone gives.

Sphere size decides the repertoire. Small spheres can only diffract the short wavelengths — blues and violets. Only the largest, most uniformly packed spheres can return red. This is worth holding onto, because it explains the entire price structure of the gem: red is not more beautiful than blue by decree. It is rarer because the physical structure capable of producing it is rarer. A stone that can flash true red can usually produce every other colour as well; a blue-only stone has told you the ceiling of what it will ever do.

The order of colours

So the value order runs: red rarest, then orange, yellow, green, and blue as the workhorse of the species. Red fire on a black body tone — the famous red-on-black of Lightning Ridge — is the summit of the opal world, and priced like it.

But here is where buyers get into trouble. The hierarchy of colours seduces people into paying for a whisper. A dull stone with a faint smudge of red is routinely priced above — and bought above — a stone with no red at all that blazes green and blue across its whole face. In our experience that trade is almost always wrong.

Brightness: the biggest lever

Brightness — how vividly the play-of-colour ignites, graded in the trade along a scale running roughly from subdued through bright to brilliant — moves price more than any other single factor. A brilliant stone announces itself from across a desk. A subdued stone needs you to hunt for its colour, tilting and squinting. Whatever the colours involved, the brilliant stone is the better gem and, over time, the one you will keep reaching for.

Buy the fire you can see across the room, not the colour you were told to want.

This is also where value hides for the buyer of ordinary means. Brilliant blue-green material is the sane luxury of the opal world: the structure is commoner, so the price is kinder, yet the visual performance can be electrifying. Saving money on colour order costs you nothing you will notice on the hand. Saving money on brightness costs you the reason you wanted an opal.

The named patterns

How the colour is organised across the face has its own vocabulary, and its own hierarchy.

Pinfire — pinpoint dots of colour, densely scattered. Charming, common, the entry point. Flash — larger areas that ignite together as the stone moves. Rolling flash — a band of fire that travels across the face as you turn the stone, one of the most theatrical effects opal offers. Broad flash — great sheets of colour lighting most of the face at once; on a bright stone, this is spectacular and still attainable. Harlequin — angular, mosaic-like patches of colour set edge to edge like a chessboard. True harlequin is extraordinarily rare; most stones offered under the name are broad-patch or flagstone material wearing a borrowed title. If a seller says harlequin, ask them to defend the word. Genuine examples are collectors' stones, and collectors know it.

As a rule of thumb, larger and more distinct colour patches command more than fine, diffuse ones — but pattern never rescues a dull stone. Brightness first, always.

Directionality

Two stones can show identical fire face-on and be very different gems. Rotate each through a full turn under your single lamp, then tilt it away from you through an arc. Some stones fire from every angle. Some fire through perhaps half the turn. Some perform only when viewed dead face-on and go to sleep the moment they tilt — and a ring spends its life tilting on a moving hand. A face-on-only stone should be priced accordingly, and it is a defensible saving for a pendant, which hangs still at a fixed angle. It is a poor choice for a ring you hope will flash across a dinner table.

The viewing discipline

When Anna assesses an opal in Sydney, the routine does not vary: one light source directly overhead, the stone face-up as it would sit in a mounting, rotated slowly through a full circle, then tilted through its arc. Face-up, because that is how the stone will live; slowly, because fast rotation blurs a stone's dead zones into apparent life. Daylight has its place too — soft indirect light from a south-facing window here in the southern hemisphere, north-facing in the north — but the single lamp is where brightness and directionality confess.

Do this with the next three opals you are shown, anywhere. One lamp. Full rotation. Face-up. You will be surprised how quickly the parcel sorts itself — and how differently it sorts from the price tags.

The Fields: Lightning Ridge to Winton — and Ethiopia

Where an opal was dug is written into what it is worth — which is why the one question every buyer should ask is the one least often answered plainly.

The Australian opal fields are places you must want to reach. Lightning Ridge is a nine-hour drive north-west of Sydney; Coober Pedy sits nine hours above Adelaide in country so hot the town lives underground; Winton is a day's drive beyond Brisbane into western Queensland. Nothing about these places is convenient, and that inconvenience is part of the price of every stone that comes out of them.

Lightning Ridge: where black opal lives

Black opal — opal with a dark body tone that makes the play-of-colour burn rather than glow — comes overwhelmingly from one small district in northern New South Wales. Lightning Ridge produces it as "nobbies", rounded nodules, and as seam opal in thin horizontal bands. The dark potch backing that gives black opal its depth is a signature of this ground; no other field on earth produces it in commercial quantity. That scarcity is the whole story of black opal pricing. When a dealer says "black opal", the unspoken second half of the sentence is "from Lightning Ridge", and you are entitled to make them say it aloud.

The South Australian fields

Coober Pedy is the volume producer: white and light opal, and the lovely transparent material called crystal opal, mined there since the First World War. Light opal is where careful buyers find honest beauty at accessible prices — a bright crystal opal with good pattern can be a fraction of the cost of a dark stone that flashes no harder.

Andamooka, to the south-east, is famous for its matrix opal — porous material that is routinely darkened by cooking in sugar solution and then acid to deposit carbon in the pores. Treated Andamooka matrix can be striking and is entirely legitimate, but the word treated must travel with the stone. Sold bare, at treated prices, it is a good buy; sold as natural black opal, it is not.

Mintabie, once a significant producer of dark and crystal opal, is closed: the South Australian government shut the township and the land was returned to the Anangu Pitjantjatjara Yankunytjatjara people. Mintabie stones still circulate, but only from old stock — worth knowing when a seller cites the field, because new production is impossible.

Boulder country

Queensland's fields — Winton, Quilpie, Opalton, Yowah, Koroit — produce boulder opal: veins of precious opal formed in cracks in ironstone, cut with the brown host rock left naturally attached as a backing. The ironstone does what the potch does at Lightning Ridge — it darkens the stone from behind — so a fine boulder opal can show black-opal fire at a substantially lower price. This is the field where value hides in plain sight.

One warning about money here. Because the ironstone backing is heavy, per-carat pricing on boulder opal is close to meaningless — two stones of identical face size can differ enormously in weight. Buy boulder opal by the stone, judged by its face, not by the carat. A seller quoting an attractive per-carat rate on boulder material may simply be selling you ironstone by weight.

What the field does to the price

As a rule of thumb from our own buying: for the same brightness and pattern, a Lightning Ridge black opal sits at the top of the market, boulder opal from Queensland well below it, dark Coober Pedy or old Mintabie material between, and light opal below that. The field is not a snobbery; it is shorthand for body tone, stability and scarcity. This is precisely why provenance gets blurred at the counter — every step up the list is a step up in price, and a vague answer always drifts upward.

Ethiopia, honestly

Ethiopian opal from the Welo district, mined in commercial quantity since the late 2000s, deserves a fair hearing. At its best it is genuinely beautiful — vivid, large, often with patterns Australian fields rarely produce — and it is dramatically cheaper. We have no quarrel with the material. We have a quarrel with silence.

Most Welo opal is hydrophane: it absorbs water. Soak it and it may turn translucent and lose its play-of-colour for hours or days; over years, some material crazes — develops fine cracks — or yellows. Its porosity also makes it easy to treat: hydrophane takes dye readily, and smoke treatment can darken it into a convincing imitation of black opal. A smoked Ethiopian stone offered as Lightning Ridge black opal at even a tenth of the Australian price is still a swindle, because you are buying a different material with a different future.

An Ethiopian opal sold as Ethiopian is a bargain; sold as Australian, it is a fraud.

None of this makes Welo untouchable. Disclosed, priced as what it is, kept away from water and worn with a little care, it is a legitimate way to own spectacular colour. Undisclosed, it is the single biggest trap in the modern opal market.

Asking the provenance question

Do this before any opal purchase. Ask three questions and ask for the answers in writing, on the invoice: Which country and which field is this from? Is it hydrophane? Has it been treated in any way — smoked, dyed, sugar-acid, or impregnated? An honest dealer answers in seconds and writes it without flinching. Hesitation, or an answer like "it's natural opal" that dodges the country, tells you what you need to know. For significant stones, an independent laboratory report confirming natural, untreated, solid opal settles the matter.

Every opal we offer is assessed in Sydney by Anna, our FGAA-qualified gemmologist, with field of origin stated wherever we can establish it and every treatment named. That is not a virtue we claim; it is simply what the invoice is for.

Doublets, Triplets, Synthetics and Treatments

Assembled stones, treated matrix and laboratory opal all have a legitimate place in the market — provided the label matches the stone — and every one of them can be caught by a buyer who knows to look at the side, not the top.

Tilt an opal ring on its side under a lamp and look at it edge-on, the way almost nobody in a shop ever does. The face-up view is where opal seduces; the profile is where it confesses. A solid stone shows one material from crown to base. An assembled stone shows a sandwich — and once you have seen the layers, you cannot unsee them.

The honest sandwich

A doublet is a thin slice of precious opal cemented to a dark backing — black potch, ironstone or black glass. The dark base does the same job a black opal's body tone does naturally: it stops light passing through, so the colour play blazes against darkness. A triplet goes one step further, adding a clear domed cap of quartz or glass over an even thinner opal slice. The cap protects the sliver and magnifies the fire.

Neither is a fake. They are legitimate constructions that put genuine opal colour on a modest budget, and generations of Australian jewellers have made them honestly. The wrong in an assembled stone is never the assembly. It is the silence about it.

An assembled opal disclosed is a bargain; an assembled opal concealed is a theft — the stone is identical, only the sentence changes.

Spotting one in under a minute

Three checks, no instruments beyond your eyes and a loupe.

The profile. Turn the stone side-on. A doublet shows a perfectly flat, ruler-straight junction between the colourful layer and the dark base — nature almost never draws a line that clean through an opal. A triplet shows two junctions, with a glassy dome on top.

The cap. A triplet's quartz dome reflects light like glass, not like polished opal, and the colour appears to sit slightly below the surface, as if under a watch crystal. Solid opal's colour lives in the surface itself.

The setting. Be doubly alert with bezel-set stones and closed backs, because they hide precisely the edges that would confess. We do not assume a bezel-set opal is assembled — but we never pay a solid-stone price for one whose profile we cannot inspect, and neither should you. Ask for the stone unset, or for the seller's written description.

One care note: doublets and triplets are glued. Prolonged soaking can cloud the cement line or lift the layers, and ultrasonic cleaners are a reliable way to ruin them. Warm water, mild soap, a soft cloth, briefly.

The price ladder, and roughly why

Solid opal sits above doublet, and doublet above triplet, usually by a wide margin at each step. The logic is volume and permanence. A solid stone is opal all the way through: it can be repolished if scratched, remounted freely, and passed down. A doublet contains perhaps a couple of millimetres of actual opal; a triplet, a film thinner than a fingernail. Damage the cap or the cement and there is little material to rescue. As a rule of thumb, a fine triplet is priced as attractive jewellery; a fine solid black opal is priced as a gemstone. Both prices can be fair. Paying the second price for the first article is the disaster this chapter exists to prevent — and it is also where value hides: a well-made, honestly sold doublet is one of the cheapest routes to genuine black-opal colour that exists.

Treated matrix: smoke and sugar

Matrix opal — colour flashing through a porous host rock — is often darkened to imitate black opal's body tone. Two old methods persist. Sugar–acid treatment, long applied to Andamooka matrix, soaks the stone in sugar solution and then acid, leaving carbon in the pores. Smoke treatment, common on porous Ethiopian hydrophane, achieves the same darkening with heated, smouldering wrappings. Under the loupe, treated material shows fine dark speckling concentrated in pores and cracks rather than an even natural tone. Treated matrix is a pleasant, affordable stone when sold as exactly that. Sold as natural black opal, it is not.

The laboratory opal

Gilson-type synthetic opal has existed since the 1970s and is easy to like: bright, regular, cheap. It is also, once known, easy to recognise. Face-up, the colour patches show a cellular, scale-like structure the trade calls lizard skin — orderly polygons with distinct edges, too tidy for geology. Side-on, the colour runs in parallel columns down through the stone, like a stack of organ pipes. Natural play-of-colour is directional chaos; synthetic play-of-colour is architecture. Newer resin-bound imitations feel warmer and lighter in the hand than stone. None of this is villainy — laboratory opal in fashion jewellery, labelled as such, harms no one.

Impregnation and dye

Porous hydrophane opal drinks whatever it sits in, which makes it the natural target for resin impregnation (to stabilise crazing-prone material) and dye (those improbable purples and electric blues are nobody's discovery; they are dye). Colour concentrating in surface-reaching cracks is the giveaway. Treatments are legitimate when disclosed. Undisclosed, they collapse at the first resale valuation, and the buyer inherits the loss.

The question that protects everyone

All of this folds into a single sentence to say before money moves: "Is this stone solid, natural and untreated — and will you put that in writing?" An honest seller answers in seconds and writes it on the receipt. A seller who hedges, reassures or takes offence has answered too, just not in words. Every opal we release is assessed in Sydney by Anna, our FGAA-qualified gemmologist, and described on paper as exactly what it is — because a description you cannot hold is a description you do not have. Turn your own opal jewellery on its side under a good lamp. Whatever you find, you will finally know what you own.

Value and the Checklist

How opal is actually priced — body tone, then brightness, then pattern — and the eight questions that separate a fair deal from an expensive lesson.

Watch a buyer work a parcel at Lightning Ridge. Each stone gets perhaps three seconds: face up on the black pad, a slow tilt under the lamp, then either the keep pile or a small push away. Nobody weighs anything until the end. The weighing is book-keeping; the deciding happened in the tilt. That habit tells you nearly everything about how opal is actually priced.

The order of value

Opal is valued in a strict sequence. Body tone comes first — the darkness of the stone itself, with the play-of-colour mentally switched off. The Australian trade grades it face-up from N1, a true black, to N9, nearly colourless, and every step down that ladder moves the price, because a dark base makes the same fire read brighter, the way stars need a night sky.

Brightness comes second, and it is the great leveller. A brilliant crystal opal on a light base will outsell a sleepy stone on a black one. Then pattern and colour range: broad, rolling flashes outrank pinfire; named patterns — harlequin above all — carry premiums; and a stone showing red alongside green and blue outprices blue-green alone, largely because red is the rarest colour the silica sphere structure produces. Note the order, though. A dull red is worth less than a brilliant blue, and buyers who chase red at any cost routinely overpay for exactly that.

Size and shape come last. This surprises people trained on diamonds, and it is where opal money is most often misspent.

Carats measure the wrong thing

Opal is quoted per carat, but carat weight rewards depth, and depth in opal is often dead weight — a thick base of colourless potch under a thin band of fire. What you are actually buying is the face: the play-of-colour across the top of the stone, measured in millimetres of spread. A 3 ct stone with a 14 mm × 10 mm face can be a better purchase than a 6 ct stone showing less. When comparing stones, set the per-carat figure aside for a moment and ask what each one costs per unit of face.

This is also why two 5 ct opals can differ a hundredfold in price with a straight face on both invoices. One is a pale N8 pinfire cut from a bulk parcel; the other an N2 black gem with broad rolling red-green fire and no sand, no crazing, no dead windows in the pattern. Both are, on paper, "natural solid opal, 5 ct". The paper is not lying. It is just not saying anything.

Two honest places to save. Free-form stones — cut to follow the colour bar rather than ground down to a calibrated oval — often deliver more face per dollar, because nothing was sacrificed to fit a standard mount. And boulder opal, with its natural ironstone backing, gives dark-toned face at a fraction of black-opal money; you accept the host rock, and the trade prices it openly for what it is.

An opal offered to you wet is answering a question you have not yet asked.

Red flags at the point of sale

A wet, oiled or waxed stone. Water and oil deepen tone, flatter the fire, and — critically — make hydrophane material and fine crazing temporarily invisible. Insist on seeing the stone bone dry, ideally after it has sat dry for days. In soft indirect daylight — a south-facing window here in Sydney; north-facing for northern-hemisphere readers — a dry stone tells the truth.

Crazing. Fine spider-web cracks across the face under a 10× loupe. Do not accept "it adds character". It is structural, and it spreads.

A seam at the girdle. Rotate the stone and study its side profile. A perfectly flat, dark junction line low on the stone suggests a doublet or triplet — a slice of opal cemented to a backing. Assembled stones are legitimate when sold as such, at assembled-stone prices. Glimpsed rather than declared, they are the point of this chapter.

"Black opal" at light-opal money. There is no such thing as a bargain black opal from someone who knows what they are holding. A grey N5 described as black, or a smoked Ethiopian stone called black opal without another word, is priced to exploit a name.

Silence on provenance. "Where was it mined?" should produce a field name — Lightning Ridge, Coober Pedy, Koroit, Winton, Welo — not a shrug or "Australia, probably."

Eight questions for any opal seller

• Is this a solid opal, a doublet or a triplet? Good answer: immediate and plain, with an offer of the loupe and the girdle.
• Where was it mined? Good answer: a field, not a continent.
• Is it hydrophane, and has it been treated — smoked, sugar-acid, dyed, impregnated? Good answer: the seller knows the words and puts the facts in writing. Treatment disclosed is commerce; treatment concealed is fraud.
• What is the body tone on the N scale? Good answer: a number, with the chart on the counter to check it against.
• Has this stone been wet or oiled recently? Good answer: "It has been dry in this tray for weeks — take it to the window."
• Is there any crazing, and do you guarantee against it appearing? Good answer: a joint inspection under the loupe and a stated return period, written down.
• What is the face-up measurement, and what does the price reflect? Good answer: millimetres before carats.
• What documentation comes with it? Good answer: a receipt stating natural solid opal — or the assembled or treated truth — plus origin, weight, dimensions and tone. The seller's claims, made permanent.

A seller with nothing to hide finds these questions boring. That is what a good answer sounds like: mild, specific, and slightly amused you asked.

Every opal we offer is assessed dry, in Sydney daylight, by Anna, our FGAA-qualified gemmologist, and described on paper exactly as she found it. We would rather lose a sale to a dry stone than win one with a wet one. Buy the opal you cannot stop looking at — after it has answered all eight questions.

Living with Opal

Opal asks a little more of its owner than sapphire does — and repays the courtesy for generations, provided you ignore the folklore and follow the physics.

The best-loved opal we ever re-polished arrived in Sydney looking finished. Thirty years on a gardener's hand had ground the dome to a grey haze, and its owner assumed the fire had simply gone out. Twenty minutes on the wheel took off perhaps a tenth of a millimetre. The colour underneath was untouched — it had been waiting behind the scratches the whole time. That stone tells you nearly everything about living with opal: it is softer than you would like, tougher than its reputation, and almost always repairable.

The honest number

Opal sits at 5.5 to 6.5 on the Mohs scale. For context, ordinary household dust is full of quartz, which is 7. This means the world itself is mildly abrasive to opal in a way it is not to sapphire at 9. A sapphire ring can be worn while renovating a house. An opal ring worn the same way will collect a fog of fine scratches within a year or two — not cracked, not dead, just dulled.

We see no point softening this. Opal is not a stone for every finger on every day, and a seller who tells you otherwise is optimising for the sale, not for your next decade.

Where opal belongs

The consequence is simple: opal is a pendant-and-earrings-first stone. At the collarbone or the ear it meets nothing harder than fabric and hair, and a fine crystal opal can pass through three generations there without a mark. This is also where value hides quietly — a top gem in a pendant will cost you the same as that gem in a ring, but the pendant version will still look new when your grandchildren inherit it.

Rings are not forbidden. They are conditional. An opal ring wants a bezel — a full collar of metal around the girdle rather than exposed claws — and an owner willing to take it off for gardening, gym, dishes and beach. A well-made bezel in 18ct gold is inexpensive insurance relative to the stone it protects, and it is the single cheapest upgrade you can specify when commissioning. Where buyers overpay is the reverse: a fragile high-domed opal in a delicate claw setting, bought for the look, back within two years for repairs that cost more than the bezel would have.

The water myths, retired

Two pieces of folklore refuse to die: that opal must be stored in water or glycerine to stop it "drying out", and that it should be oiled. Both are wrong for solid Australian opal, and the second is actively harmful.

Australian precious opal from Coober Pedy, Lightning Ridge, Mintabie or the Queensland boulder fields formed in some of the most stable silica on earth. It contains water, but that water is bound within the structure; it does not evaporate on your dressing table, and it cannot be topped up from a glass. Soaking does nothing. Glycerine and oils are worse than nothing — they seep into any surface-reaching feature, attract grime, and can leave a stone looking greasy and darker than the day you bought it. If a seller's care card tells you to oil an Australian opal, treat it as you would a jeweller who cannot spell carat.

The water folklore exists because of a different stone, and knowing which stone you own is the whole game.

The exception — and the reason the myth survives — is hydrophane opal, most of it Ethiopian. Hydrophane is porous by nature: it drinks water, perfume, hand soap and skin oil, changing colour and transparency as it does, sometimes temporarily, sometimes not. Hydrophane must be disclosed at sale, in writing. If you own one, keep it away from liquids entirely. If you were never told which type you have, that silence tells you something about the seller.

What actually damages opal

The real enemies are duller than folklore. Never put opal in an ultrasonic cleaner; the vibration can propagate any internal weakness. Never subject it to heat shock — the classic accident is hot soapy washing-up water straight after a cold morning, or a jeweller's torch used near the stone during a resize; a competent bench removes the opal first. Prolonged storage in aggressively dry environments — a dehumidified safe, a bank vault sachet-packed with desiccant, a sunny display case — is worth avoiding as a matter of caution, particularly for hydrophane and for any stone whose provenance you are unsure of. Room conditions in a drawer, wrapped in a soft cloth and kept apart from harder gems that could scratch it, are all a solid opal ever asks.

Cleaning is correspondingly simple: lukewarm water, a drop of mild detergent, a soft cloth or the softest brush you own, and a thorough dry. Doublets and triplets — assembled stones with glued layers — should never be soaked at all; wipe them with a barely damp cloth so moisture cannot creep into the adhesive line.

Scratches are maintenance, not mourning

Because opal is soft, it scratches; because it is opal, the scratches are shallow. A professional re-polish removes a whisker of material and returns the dome to glass. In our workshop this is routine maintenance, like servicing a watch — done every decade or so on a working ring, perhaps once a generation on a pendant. Budget for it mentally when you buy, and a scratched opal stops being a tragedy and becomes a Tuesday.

Wear it anyway

Every argument in this chapter could be read as a case for the safe. It is the opposite. An opal locked away is a coloured pebble; its play-of-colour only exists in moving light, on a moving person. The heirloom opals we see — the ones with letters and stories attached — are invariably the worn ones, re-polished twice, remembered on a specific grandmother at a specific table. Set it sensibly, clean it gently, take the ring off before the garden. Then wear it, because a stone this alive was never meant to be stored.

Referenced in this handbook: Australian opals. Every stone we sell is assessed in-house by our FGAA-qualified gemmologist, with treatment disclosed.