Moissanite vs Lab Grown Diamond: The 2026 Australian Comparison

We sell both. We have no preference, and no commercial reason to talk you into either one.

That sounds like a small thing. It is not. Almost every comparison of moissanite and lab grown diamond you will read online is published by a business that sells one of them, and it reads exactly the way you would expect. The moissanite sellers tell you diamonds are an inflated marketing construct. The diamond sellers tell you moissanite looks fake. Both are talking their book. Our lab grown diamond designs start at AU$1,350 and our moissanite designs start at AU$800, and either way we make the ring, so the honest version costs us nothing.

Here is what actually separates them.

What each one actually is

Lab grown diamond is crystallised carbon. Same chemistry and same cubic crystal structure as a mined diamond, grown in a chamber over weeks rather than in the mantle over aeons. A diamond tester reads it as diamond because it is diamond.

Moissanite is silicon carbide. Carbon and silicon in a hexagonal crystal structure. It occurs in nature only in vanishingly small quantities, mostly in meteorite fragments, which is why essentially all of it on the market is grown. It is a genuinely different mineral with its own properties, not an imitation of anything.

That difference in structure is where every other difference on this page comes from.

Is moissanite a lab grown diamond?

No. It is a different mineral.

The confusion is completely understandable, and I do not blame anyone for it. Both stones are grown in a laboratory. Both are colourless. Both are sold in the same shapes, in the same settings, at the same jewellers, often on the same page. The phrase "lab grown" describes how a stone was produced, not what it is made of, so a lab grown moissanite and a lab grown diamond sit under the same umbrella term while being chemically unrelated.

The useful mental model: lab grown diamond is diamond made in a different place. Moissanite is a different stone entirely, which happens to also be made in a lab.

Hardness and durability

Diamond is 10 on the Mohs scale. Moissanite is 9.25. Sapphire, for reference, is 9.

In practical terms both are hard enough for daily wear over a lifetime, and this is a much smaller differentiator than the numbers suggest. The Mohs scale is ordinal, not linear, so the gap between 9.25 and 10 is wider than it looks on paper. But the things that scratch a 9.25 stone in ordinary life are limited to diamond itself and a handful of industrial abrasives. Sand will not touch either. Steel will not touch either.

Where the difference shows up is facet edges over decades. A moissanite worn hard for thirty years may show very slight softening on the sharpest edges of the crown facets, visible under magnification. A diamond will not. If you work with your hands in a hostile environment, that is a real if minor point for diamond.

Neither stone is immune to chipping. Hardness is resistance to scratching. Toughness is resistance to breaking, and diamond has cleavage planes, meaning a sharp knock at the right angle on the point of a marquise or the corner of a princess cut can take a chip out of it. Moissanite is actually slightly tougher than diamond in that specific respect. Anyone who tells you a diamond cannot chip has not worked at a repair bench.

The optics, and why moissanite throws more colour

This is the real difference between the two stones, and it is the one you can see across a room.

Two numbers matter.

Refractive index is how much the stone bends light, which drives how much of the light entering the top comes back out the top instead of leaking through the bottom. Diamond is 2.42. Moissanite is 2.65 to 2.69. Moissanite is the brighter stone, marginally.

Dispersion is how much the stone splits white light into its component colours, which is what the trade calls fire. Diamond is 0.044. Moissanite is 0.104. That is not a marginal difference. Moissanite disperses light more than twice as strongly as diamond, and that is why a moissanite under a spotlight or in direct sun flashes distinct reds, blues and greens where a diamond returns more white light and finer, tighter flashes of colour.

Moissanite is also doubly refractive: light entering the stone splits into two rays. Cutters orient the stone to hide this through the table, but look in from an angle under magnification and you can see facet junctions appear doubled. Diamond is singly refractive and never does this. It is one of the ways a gemmologist separates them in seconds.

There is one more practical number. Diamond has a specific gravity of 3.52 and moissanite 3.21, so a moissanite is about ten per cent lighter than a diamond of the same physical size. This is why moissanite is properly sold by millimetre measurement rather than carat weight. A stone described as "1 carat equivalent" moissanite means 6.5mm across, the same face-up size as a one carat round diamond, while actually weighing a little under a carat. Compare millimetres, not carats, or you will compare the wrong thing.

The disco ball question

At small sizes, under 1 carat equivalent, most people cannot reliably pick moissanite from diamond in normal light. The extra fire reads as liveliness.

Above about 1.5 carat equivalent, and especially in direct sunlight or under LED downlights, the difference becomes obvious to anyone paying attention. A large moissanite throws big saturated rainbow flashes. Some people love this. It is the reason they chose the stone. Others look at it and find it too much, and describe it as looking like a disco ball or a prism.

I cannot tell you which of those two people you are, and neither can a website. This is the single strongest argument for looking at both in person before you commit, in daylight and under artificial light, at the actual size you are considering. It is a preference, not a defect, and it is the thing people most often change their mind about after seeing the stones side by side.

Round brilliants maximise the effect because their facet arrangement is designed to maximise dispersion. Step cuts, emerald and asscher, minimise it dramatically because their long parallel facets return broad flashes rather than scattered spectral colour. If you like moissanite but not the rainbow effect, an emerald cut solves the problem almost entirely. That is a genuinely useful trick and hardly anyone mentions it.

Price at the same size

Moissanite costs a fraction of lab grown diamond at the same face-up size, and the gap widens as the stone gets bigger. At around 1 carat equivalent it is a meaningful saving. At 3 carat equivalent it is the difference between a decision you make quickly and a decision you think about for a month.

Lab grown diamond prices have fallen substantially since 2020 as production capacity scaled up, which has narrowed the gap at smaller sizes. It has not closed it and it is not going to.

The other thing that changes with the stone choice is where the rest of the budget goes. On a moissanite ring, the metal, the setting labour and any accent stones make up a much larger share of the total, so paying for a properly made setting is proportionally more of the cost and proportionally more important. On a lab diamond ring, the centre stone dominates.

Certification

Different systems, and the difference is real.

Lab grown diamonds are graded by diamond laboratories on the standard diamond scales. Ours are IGI certified, with the report number laser inscribed on the girdle so you can look up the grading yourself. Colour on the D to Z scale, clarity on the IF to I scale, and for round stones an actual cut grade. That report is a meaningful, independent, comparable document. We explain how to read one here.

Moissanite is graded by GRC, which confirms the stone's identity, dimensions, colour range and cut quality. It is a real certificate from a real laboratory and it is worth having. It is not the same instrument as a diamond report, because moissanite is a manufactured material with far less variation between stones, so there is less to grade. Two colourless moissanites of the same size from reputable production are close to interchangeable in a way that two lab diamonds of the same carat weight genuinely are not.

The practical upshot: with a lab diamond, the certificate is doing a lot of work, and you should read it. With moissanite, the certificate confirms what you bought, and the cut quality and the setting matter more than the paperwork.

Resale, for both

Neither one holds value. I am not going to dress this up.

Lab grown diamonds depreciate, and depreciate faster than most buyers expect, because production costs keep falling and a comparable new stone gets cheaper every year. Moissanite has effectively no secondary market at all: it is priced low enough new that nobody shops for it used.

For completeness, mined diamonds are not the investment they are marketed as either. A private seller buys at retail and sells at trade, and that spread eats most of the value before you start. The difference is that a mined stone has a floor and the lab grown ones do not have much of one.

Choose either stone on the basis that you want to wear it. Neither is a store of value, and any seller implying otherwise is selling you something other than a ring.

Scored comparison

Scores are out of 10, from our bench, for a ring worn every day. Where the difference is a matter of taste rather than quality we have said so instead of pretending one wins.

Category	Lab grown diamond	Moissanite	Notes
Hardness	10	9	10 vs 9.25 on Mohs. Both fine for daily wear. Diamond holds facet edges better over decades.
Chip resistance	8	9	Diamond has cleavage planes. Moissanite is slightly tougher against a knock.
Brightness	9	10	Higher refractive index gives moissanite a small edge in light return.
Fire	Taste	Taste	Diamond 0.044 dispersion, moissanite 0.104. More is not better, it is different.
Looks like a diamond	10	8	Moissanite is convincing under 1ct equivalent, distinguishable above 1.5ct in bright light.
Price at same size	6	10	Moissanite is a fraction of the cost, and the gap widens with size.
Certification depth	10	7	IGI diamond report with full grading and girdle inscription vs GRC identity and quality report.
Resale value	3	2	Both poor. Buy to wear, not to hold.
Colour stability	10	10	Neither yellows, clouds or changes over time. Both are chemically inert.
Range of shapes and sizes	9	9	Both available in every standard shape. Very large sizes are far more attainable in moissanite.
Ethical simplicity	9	9	Both avoid mining entirely. Energy source of the production facility is the live question for both.

Add the numbers up and you get a near tie, which is the honest result. The scores are not the point. The rows where you disagree with our weighting are the point.

How to decide

Four questions, in order.

Do you want the stone to be diamond? Some people care about this and some do not, and neither position is wrong. If the answer is a firm yes, stop reading, buy the lab diamond, and be happy. Trying to talk yourself out of it will not work, and I have watched people try.

How big is the centre stone? Under 1 carat equivalent, the visual difference is small and the price difference is smaller, which pushes towards diamond. Above 2 carat equivalent, the price difference becomes large and the visual difference becomes obvious, which makes it a real decision rather than a default.

Do you like fire or do you find it distracting? Look at a large moissanite in direct sunlight before you answer. If your reaction is delight, the choice is made and you have saved a great deal of money. If your reaction is that it looks busy, you want diamond, or you want moissanite in a step cut.

Where do you want the money to go? A moissanite centre with the savings spent on a heavier band, a better setting and a wider metal choice is a genuinely good ring. So is a modest lab diamond in a simple solitaire. Both of those beat an overreached centre stone in a setting that was not paid for properly, which is the most common mistake we see.

If you are still stuck, come and look. We make everything in our Southbank, Melbourne studio and you can book an appointment to see both stones in the same light, at the same size, in the same setting. Fifteen minutes with the two of them in your hand settles this faster than any article can. If you are not in Melbourne, we do design consultations by video call and we will send you a free ring sizer before anything is cast.

Or browse first: moissanite engagement rings and lab grown diamond engagement rings.

FAQ

Is moissanite a lab grown diamond?

No. Moissanite is silicon carbide, a different mineral with a different crystal structure. Lab grown diamond is crystallised carbon, chemically identical to mined diamond. Both are grown in a laboratory, which is where the confusion comes from, but they are not the same stone.

Can a jeweller tell the difference between moissanite and a diamond?

Yes, quickly. A moissanite tester separates them on electrical conductivity in seconds, and under magnification a gemmologist will see doubled facet junctions in moissanite that never appear in diamond. Neither test is something you can do at home.

Does moissanite look fake?

Not at smaller sizes. Above roughly 1.5 carat equivalent, in bright light, the extra dispersion produces rainbow flashes that read as different from diamond to people who are paying attention. Whether that reads as fake or as beautiful is genuinely a matter of taste, and it is why we recommend seeing one in person.

Which is better value, moissanite or lab grown diamond?

Moissanite is cheaper at every size and the gap widens as the stone gets larger. Value depends on what you want, though. If having a diamond matters to you, a moissanite is not good value at any price, and if it does not matter to you, moissanite is very hard to beat.

Do both come with a certificate?

Yes. Our lab grown diamonds are IGI certified and laser inscribed on the girdle with the report number. Our moissanite is GRC certified. Both certificates come with the ring.

Which one do you recommend?

Neither, in the abstract. We make both and the margin is not the deciding factor for us. The answer depends on whether you want the stone to be diamond, how large you want it, and how you react to fire, and the only way to answer the last one is to look.