How Do Moissanite and Lab-Grown Diamonds Differ After Years of Wear?

Last updated: August 2026

Why does moissanite look more like a disco ball at larger sizes?

Two numbers explain it. Dispersion — the splitting of white light into spectral colours, which the trade calls fire — is 0.044 for diamond and 0.104 for moissanite, roughly two and a half times as much. Refractive index, which governs how strongly the stone bends and returns light, is 2.42 for diamond against 2.65 to 2.69 for moissanite. More light is returned, and more of what is returned arrives as coloured flashes rather than white ones.

Size is the multiplier. Fire is produced by facets, and a bigger stone has bigger facets, so each individual flash covers more of your field of view. At 4 mm in an ear, the difference between the two stones is subtle and many people cannot call it. At 8 mm on a hand, under a spotlight or in direct sun, moissanite throws large, saturated rainbow flashes that read as distinctly not-diamond to anyone who looks at jewellery often. This is a matter of taste rather than quality — but it is a taste decision that gets louder as the stone gets bigger, and it is worth making it at the size you intend to buy rather than at the size in the photograph.

Moissanite is also doubly refractive, so at larger sizes and under magnification the facet edges can appear doubled. The existing moissanite and lab-grown diamond comparison covers the property table in full; what follows is the part that only shows up after the first few years.

What does the difference between Mohs 9.25 and 10 mean after years of wear?

Less than the half-point suggests, and more than it sounds. The Mohs scale is ordinal — it ranks which mineral scratches which, and says nothing about the size of the gaps. The gap between 9 and 10 is by far the largest on the scale; diamond is several times harder in absolute terms than the materials just below it.

In practice neither stone is at risk from ordinary household dust, which is largely quartz at Mohs 7 and cannot mark either one. The realistic hazard is contact with something harder: another diamond. A diamond can only be scratched by another diamond. Moissanite can be scratched by diamond and by other moissanite. If you wear a diamond ring on the adjacent finger, or stack rings in a drawer, that is where facet-edge softening starts — first as a loss of crispness on the girdle and the table edges, which reads as slightly less sparkle long before anyone would call it a scratch.

The counterpoint that flatters moissanite: hardness is not toughness. Diamond has perfect cleavage in four directions, so a sharp knock on an exposed girdle can chip a diamond in a way that its Mohs 10 does nothing to prevent. Setting style protects against that far more than hardness does — a bezel or a low-profile setting shields the girdle, a high solitaire does not.

How do moissanite and lab-grown diamonds read on a diamond tester?

A thermal-probe tester measures how quickly heat moves through the stone. Both diamond and moissanite are excellent thermal conductors, so a thermal-only tester reads moissanite as diamond. This is the single most common testing mistake, and it has been for decades.

A combination tester adds an electrical conductivity check. Moissanite is a semiconductor and conducts; most diamond does not, so the second probe separates them. Two caveats matter. Some boron-bearing diamonds are electrically conductive and can be flagged as moissanite by that same test — an uncommon but real false positive. And no handheld tester distinguishes a lab-grown diamond from a mined one; both are diamond, both read as diamond, and telling them apart requires laboratory instruments, which is exactly what a grading report is for.

What is resale and appraisal actually like for each?

Honestly: neither is an asset. Lab-grown diamonds have a resale market, but it is thin and prices realised are far below what was paid, partly because production costs have fallen year over year and a buyer today can grow a new stone rather than take yours. Moissanite resale is thinner again — there is no established secondary trade to speak of, and a piece is worth what the metal is worth plus whatever a private buyer will pay.

Appraisal differs in kind. A lab-grown diamond has a grading report, so an appraiser can price a documented specification. Moissanite has no equivalent 4Cs framework, so an appraisal usually describes the stone by size and quality tier rather than by graded attributes. That difference matters at the moment of a claim rather than at the moment of purchase. Anyone buying either stone as a store of value has misunderstood both; buy for wear.

How does insurance and replacement differ?

Insurers price a scheduled item from a written valuation, and a grading report makes that valuation straightforward — the specification is on paper, and a replacement can be sourced to match it. For a lab-grown diamond that means a lost stone can be replaced to the same graded specification, which is a genuinely useful property.

Moissanite is easier in a different way: it is inexpensive enough that many owners simply do not insure it and replace it out of pocket if it is lost. That is a perfectly rational answer, and it is one of the quiet advantages of the stone. What both share is a manufacturing risk that has nothing to do with the stone — settings loosen and posts wear, and that is what a warranty covers. Beyond Carat carries a lifetime manufacturing warranty covering defects in materials and workmanship, set out on the warranty page. The concession attached: Beyond Carat does not currently publish the terms of a trade-in or upgrade programme. A “Lifetime Upgrades” line survives in one legacy corner of the site with no supporting policy behind it, so treat it as unconfirmed — a buyer who expects to move up in size in a few years and put the original stone toward it should ask directly before counting on that route.

Who is each stone genuinely right for?

Moissanite is genuinely right for someone whose priority is size per dollar, who likes the extra fire rather than tolerating it, who works with their hands and would rather not think about an expensive stone, or who wants a travel piece. It is not a compromise diamond — it is a different gemstone with its own optics, and at smaller sizes the visual case against it is weak.

A lab-grown diamond is right for someone who wants the classic white brilliance rather than rainbow flashes, who wants an independently graded stone, who intends to insure the piece, or for whom the word diamond carries meaning that a substitute does not. Its permanence is a settled matter: a lab-grown diamond’s optical properties will never fade or cloud. If you are still weighing the categories rather than the stones, how lab-grown diamonds are graded is the better next read.

Frequently asked questions

Does moissanite get cloudy or scratched over time?

At Mohs 9.25 moissanite is not marked by ordinary dust, but it can be scratched by diamond and by other moissanite, so facet edges can soften over years if it is stored or worn against diamond jewellery. Its dispersion and refractive index do not change.

Will moissanite pass a diamond tester?

On a thermal-probe tester, yes — both stones conduct heat well, so moissanite reads as diamond. A combination tester adds an electrical conductivity probe, which flags moissanite. No handheld tester can distinguish a lab-grown diamond from a mined one.

Which holds its value better, moissanite or a lab-grown diamond?

Neither holds value in any meaningful sense. Lab-grown diamond resale is thin and well below purchase price; moissanite resale is thinner still. The practical difference is documentation — a graded diamond can be appraised and replaced to specification, which matters for insurance rather than for resale.