What the same money buys
This is a shopping question, so here is a shopping answer. Fifteen hundred dollars, spent on the loose stone, in five different materials. Every circle below is drawn at the real face-up size that budget reaches, on one scale.
$1,500 on the stone, five waysRound brilliants, drawn at their true face-up widthAustralian retail ranges for loose stones in 2026, worked back to the weight the budget reaches. Diamond figures are for a well cut round in G colour and VS2 clarity; the imitations are sold on size and clarity rather than graded, so their per-carat prices vary more between sellers than the stones vary between each other.
The imitations win the size argument, and it is not close. If the only thing you are optimising for is how much stone sits on a finger, cubic zirconia beats everything ever mined and costs less than the ring box.What has changed is the row in the middle. Ten years ago the honest choice was a small natural diamond or a large imitation, and for most budgets the imitation was the only way to have any presence on a hand at all. Lab-grown diamond removed that trade. A 1.3 carat lab-grown round now costs what a big moissanite used to, and it is a diamond: same carbon, same crystal, same grading scale, same hardness, graded by the same labs.Natural diamond0.25 ct · 4.1 mm acrossAround $6,000 a carat for a well cut G VS2 round.
Lab-grown diamond1.3 ct · 7.1 mm acrossAround $1,100 a carat for the same grades, from an IGI graded stone.
Moissanite4 ct · 10.3 mm acrossAround $350 a carat, less again as the stones get bigger.
White sapphire5 ct · 11.1 mm acrossAround $300 a carat for a clean, well cut stone.
Cubic zirconia10 ct · 14.0 mm acrossUnder $20 a carat, so the budget is not the limit. Taste is.
The short versionIf you want the cheapest thing that looks like a diamond, buy cubic zirconia and plan to replace it. If you want the cheapest thing that is a diamond, buy lab-grown. Most people asking this question want the second one and do not realise it now sits in their budget.
The six stones people mean
The trade word for a stone that imitates diamond without being one is a simulant. It is worth knowing, because it is the word a seller has to use when they cannot use the word diamond. Six turn up in Australian shops and on Australian marketplaces, and each one gives itself away differently.
What you are actually being offeredHardness bars drawn to one scale. Prices are Australian retail for the loose stone.There isn't one you can see. Separating lab-grown from mined takes a screening instrument, and the stone arrives with an IGI or GIA report that says laboratory-grown on the front. This is the only row on the list that is a diamond.Rainbow. Moissanite splits light into colour two and a half times as strongly as diamond, which reads as flashes of green and orange where a diamond flashes white. Under a loupe the back facet edges appear doubled. Both tells get stronger above about 1.5 ct.Weight, then wear. CZ is about 1.7 times as dense as diamond, so a stone cut to the size of a 1 ct diamond weighs nearer 1.7 ct. Within a year or two of daily wear the polish has gone soft and the stone looks like frosted glass.It doesn't sparkle enough to be mistaken for a diamond. Sapphire bends light gently, so a white one reads as clear and glassy, and it looks grey between cleans. Hard-wearing, and honestly not a diamond substitute.Flat and watery from the moment you see it, and chipped along the girdle inside a couple of years. Topaz splits cleanly in one direction, so a knock that a sapphire shrugs off takes a flake out of it.The best natural imitation for fire, and the softest thing here. Facet edges round off and the stone loses its crispness. Doubled facet edges give it away, the same as moissanite.Hardness is the Mohs value, which is a ranking rather than a measurement: see the section below on what that number hides. Prices move with the exchange rate and with how much cutting labour a seller has paid for.
A seventh worth naming, because people are still sold it: quartz, marketed under place names like Herkimer diamond and Bristol diamond. It is rock crystal. It has the optical character of a clean piece of window glass, and the only thing diamond about it is the word in the listing.Glass and cut lead crystal sit below all of it. They are what costume jewellery uses, they are perfectly honest at the price, and nobody looking at one across a table is in any doubt.Lab-grown diamondCarbon. The same crystal as a mined diamond.
Mohs 10
$800 to $1,800 a caratMoissaniteSilicon carbide, grown in a furnace.
Mohs 9.25
$200 to $600 a caratCubic zirconiaZirconium dioxide, stabilised with yttrium.
Mohs 8 to 8.5
$5 to $30 a caratWhite sapphireCorundum, the same mineral as a blue sapphire.
Mohs 9
$150 to $400 a caratWhite topazAluminium fluorosilicate.
Mohs 8
$20 to $80 a caratWhite zirconZirconium silicate. A natural stone, not cubic zirconia.
Mohs 6.5 to 7.5
$80 to $250 a caratWhy moissanite gets spotted
Sparkle is three separate things, and mixing them up is what makes this conversation confusing. Brilliance is white light bounced straight back at you. Fire is white light split into its colours on the way through, so you see green and orange and violet. Scintillation is the pattern of flashes as the stone, the light or your head moves.Two measured properties set the first two. How strongly a stone bends light decides how much comes back. How unevenly it bends the different wavelengths decides how much of that arrives as colour. Plot every stone on the page against both and the shape of the problem appears.
Every stone on this page, on the two properties that matterRefractive index across, dispersion up. Both are measured constants of the material rather than opinions about it, and the dashed lines run through diamond.
Diamond is not top of either axis. Cubic zirconia carries more fire than it, and moissanite sits alone in the corner above and to the right of both, which is the whole story. Two and a half times the fire sounds like winning, and in a jeweller's spotlight it looks like it. Under a Queensland midday sun or a restaurant's LED downlights it reads as a rainbow where a diamond reads as a white flash, and that overshoot is what people are describing when they say a stone looks fake. Nothing to do with quality. Too much of a good thing.There is also a mechanical tell that takes ten seconds. Moissanite is doubly refractive: light entering it splits into two paths, so looking through the flat top at a slight angle with a loupe, the back facet edges appear as two lines instead of one. Diamond is singly refractive and never doubles. Zircon doubles too, and strongly. Cubic zirconia and sapphire do not.Splits more of it into colour
Quartz
White topaz
White sapphire
White zircon
Cubic zirconia
Diamond
Moissanite
Bends light more strongly, so more comes back
Values as published in standard gemmological tables: diamond 2.42 and 0.044, moissanite 2.65 to 2.69 and 0.104, cubic zirconia 2.15 and 0.060, zircon 1.93 to 1.99 and 0.039, sapphire 1.76 and 0.018, topaz 1.62 and 0.014, quartz 1.54 and 0.013. Cut quality still decides how much of any of it you actually see.Why the pen-shaped tester is not the answerCheap diamond testers measure how fast a stone carries heat away, and silicon carbide carries heat almost as well as diamond, so moissanite passes as diamond on a thermal probe. That is why the trade moved to combination testers that also check whether the stone conducts electricity. If someone waves a pen tester at a stone and it beeps, you have learned that it is not glass and not cubic zirconia. You have not learned that it is a diamond.
What the Mohs number hides
Diamond is 10 and moissanite is 9.25, so they look like near neighbours. They are not. Mohs is an ordinal scale: it records which mineral scratches which, in order, and says nothing about by how much. Measure the same materials with an indenter and the gaps open up.
Resizing a ring or retipping a worn claw means heat near the stone. Diamond, moissanite and sapphire take a torch without complaint. Cubic zirconia can craze and go cloudy, and topaz can fracture, so both usually have to be unset first and reset afterwards.That bench detail is the running cost nobody mentions at the point of sale. Ask before you buy whether the stone can stay in the ring during ordinary repairs, because on a soft simulant a twenty-minute job becomes an hour, every time, for the life of the ring.
The same seven stones, on a measured hardness scaleBars are approximate Knoop hardness from published tables, as a share of diamond. The number at the end of each row is the familiar Mohs grade, printed alongside so the compression is visible: one step from 9¼ to 10 on Mohs is nearly a threefold jump in what a diamond will actually resist.
The number that decides how a ring ages is not 10 though. It is 7. Ordinary dust, on a Melbourne windowsill or a Perth building site, contains quartz, and quartz is Mohs 7. Anything at or near 7 is being sanded a little every day it is worn. That is why cubic zirconia goes cloudy, why white topaz loses its edges, why zircon softens, and why moissanite and sapphire hold their polish for decades.Hardness is only half of durability, and the half people quote. The other half is toughness: resistance to chipping rather than scratching. Topaz is hard and not tough, because it cleaves cleanly in one direction. Zircon is brittle at the girdle. Diamond, for all its hardness, has cleavage planes too, which is how a doorframe occasionally takes a corner off one.Diamond
10
Moissanite
9¼
Sapphire
9
Topaz
8
CZ
8½
Zircon
7
Quartz
7
What an insurer seesA contents policy pays to replace what was lost. A $40 stone in a $900 setting is a $940 claim, less the excess, so there is not much point specifying it separately. A valuation on an imitation stone values the metal and the labour and says so on the certificate. If part of the plan is a ring that is worth something, that plan needs a diamond in it.
About that phrase
People arrive at this topic through an old expression, so it is worth answering directly. A poor man's diamond is not a mineral. The phrase has been attached to white sapphire, white topaz and rock crystal quartz for well over a century, to cubic zirconia from the 1970s once it became cheap to make, and to moissanite since about 2015. It describes an assumption about the buyer, not a stone.We do not use it, for the obvious reason and for a second one. It implies the only motive for choosing something other than a diamond is that you could not reach one, and that is frequently untrue. Someone choosing a sapphire because their grandmother wore a sapphire is not economising.The phrase does get attached to one thing wrongly and often enough to correct. A lab-grown diamond is not cubic zirconia and is not a simulant of anything. Cubic zirconia is zirconium oxide, a different substance that has been made to look like diamond. A lab-grown diamond is carbon in diamond's crystal structure, grown in a reactor rather than in the mantle, graded by GIA and IGI on the same scale as mined stones and sold with a report that says so. Our guide on telling lab-grown from natural covers what genuinely separates those two, which is provenance and nothing else.
The four precious stones
The other question that arrives beside this one: what are the top four precious stones? Diamond, ruby, sapphire and emerald. The trade calls them the big four, and everything else has historically been filed as semi-precious.
The big fourWhat each one is underneath the trade name, and whether it survives a handGIA and most of the modern trade avoid the term semi-precious, because it implies a ranking of rarity and value that the two categories do not actually describe.
The division is Victorian marketing rather than gemmology, and the clearest proof is amethyst. It sat in the precious category for centuries and was priced like it, until enormous deposits were found in Brazil and Uruguay in the 1800s and it became one of the cheapest stones in the case. Nothing about the mineral changed. Meanwhile a fine unheated Kashmir sapphire or a Burmese ruby will outprice almost any diamond per carat, from the semi-precious side of a line that supposedly ranks them below it.This matters here because a coloured stone is the one alternative on this page we would recommend without hedging. It is not pretending to be a diamond. Sapphire is Mohs 9, comes in every colour including colourless, and Australia mines its own in central Queensland and around Inverell. If the appeal of an imitation is really that you want to spend less on something that is unmistakably itself, a sapphire does that and a cubic zirconia does not.Diamond
Carbon, mined or grown.Mohs 10
The default because it survives anything, not because it is the rarest thing in the case. Plenty of coloured stones are rarer.Ruby
Corundum, coloured red by chromium.Mohs 9
As hard-wearing as a sapphire, because it is a sapphire with different trace elements. Fine Burmese material outprices diamond per carat.Sapphire
Corundum, in every colour but red.Mohs 9
The one alternative we would put in an everyday engagement ring without adding a caveat. Australia mines its own, mostly in Queensland and northern New South Wales.Emerald
Beryl, coloured green by chromium or vanadium.Mohs 7.5 to 8
Hard enough on paper and brittle in practice, because the colour comes with internal fractures. Beautiful, and it wants a bezel and a careful owner.When an imitation is right
There are cases where a simulant is the sensible purchase and anyone telling you otherwise is selling. There are more cases where it is a false economy. The line between them is mostly about carat weight and about whose decision it is.
Where we would land, given the ring
The arithmetic behind the left column is worth stating plainly, because it is the only genuinely strong argument for an imitation. At 1 carat, moissanite saves you something like seven hundred dollars against a lab-grown diamond. At 3 carats it saves you four thousand or more, because diamond prices climb steeply with size and moissanite prices barely do. If the look you want is large and the budget is fixed and small, that gap is real and no amount of principle closes it.Between about half a carat and two, which is where most Australian engagement rings sit, the gap is a few hundred dollars on a purchase of several thousand. Our budget guide works through what that money reaches once the setting is in the sum. At those sizes we would spend the difference every time and stop thinking about it.For the record, we sell lab-grown and natural diamonds and we do not sell simulants. Not out of snobbery: at the sizes most people buy, the price difference stopped being the point, and we would rather not set a stone we expect to look worse in five years than it does today. If what you want is a four carat moissanite, we are cheerfully the wrong shop, and Australia has good ones.Buy the imitation
You want 3 carats and up, and the whole budget is under two thousand. This is where the price gap reopens and moissanite is the only way to get there.
It is a travel ring, a stand-in while the real one is being made, or a copy of something you own and would rather not wear to the shops.
The person wearing it has told you they do not care about diamond. That is information, not modesty.
It is a fashion piece with a few years in it, not a ring that has to look the same in 2060.
Buy the lab-grown diamond
You are shopping between about 1 and 1.5 carats. The difference is a few hundred dollars and it buys you the material, the report and a resale floor.
It is a proposal and the two of you have never discussed it. A surprise imitation is a decision made on someone else's behalf.
You want it insured for something, valued honestly, and resettable in thirty years.
You want a jeweller to be able to size it or retip a claw without unsetting the stone first.
Not sure which side of the line you are onTell us the budget, the size you have in mind and whether the ring is a surprise. We will tell you what a diamond reaches at that number and where an imitation would genuinely buy you more, including when the answer is that you should go elsewhere and buy the big stone.
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