What “more fire” actually means
Three different things happen when light hits a cut stone, and the trade uses three different words for them. Most people mix them up, and some jewellers are happy about that.
- Brilliance is the white light bouncing straight back at you.
- Scintillation is the sparkle as the stone or your hand moves.
- Fire is the rainbow. Light entering the stone, splitting into its colours, and coming back out as flashes of red, blue and green.
Fire is measured as dispersion. A diamond’s is 0.044. Moissanite’s is 0.104. That is not a marketing rounding, it is a measured optical constant, and it means moissanite throws roughly two and a half times the coloured light a diamond does.
In practice: in a restaurant, at night, under those small warm ceiling lights, a moissanite will flash colour across the table in a way a diamond simply does not. That is the whole thing. That is what people notice, and it is the one thing a ring is actually for.
The part that does not flatter us
Some people find high dispersion too much. In direct sunlight a large moissanite can throw so much colour that it reads as showy, and there is a subset of buyers who look at it and think “disco ball.” That is a real aesthetic objection and we are not going to pretend it is not. If you want a stone that mostly returns white light and stays quiet, a diamond does that better. Ask us for the smaller carat weights, or a step cut like an emerald or asscher, which mutes fire considerably.
Will anyone be able to tell?
Across a table, no. Not your friends, not her mother, not the people at work. The two stones look enormously alike and the differences run the wrong way for a casual observer, because the moissanite is the brighter of the two.
Under a loupe, a jeweller can tell in seconds, and you should know exactly how. Moissanite is doubly refractive. Look through the top of the stone at magnification and the facet edges on the far side appear doubled, like slightly out-of-register printing. A diamond is singly refractive and shows no doubling. Any competent gemologist checks this first.
There is also a testing issue worth knowing. A basic diamond tester measures thermal conductivity, and moissanite conducts heat well enough that it will read as diamond on a cheap tester. Testers that also measure electrical conductivity separate them instantly. If someone waves a pen-shaped gadget at your ring and announces it is a diamond, they have not proven anything.
So: a professional can tell, easily, and will. Which is exactly why the strategy of hoping nobody finds out is a bad one, and the strategy of saying it out loud is a good one.
Will it last?
Yes, and this is where the comparison gets interesting rather than apologetic.
Hardness is not toughness. Hardness is resistance to scratching, and a diamond wins that at 10 to 9.25. But moissanite at 9.25 is still the second hardest thing you are likely to encounter. Ordinary life contains almost nothing that scratches either.
Toughness is resistance to breaking, and here the diamond has a genuine flaw. A diamond has perfect cleavage in four directions, meaning there are planes inside the crystal where the atomic bonds are weaker. Strike a diamond at the wrong angle against a door frame and it can split cleanly. It is rare, but every jeweller has seen it. Moissanite has no cleavage plane at all. There is no line along which it wants to break.
It will not cloud. It will not go dull. It does not need re-cutting, and it does not turn yellow with age. Warm water, a drop of dish soap and a soft toothbrush, roughly once a month, is the entire maintenance schedule.
What it costs, and why
Roughly a tenth of a diamond of the same size and grade. That is not a discount and it is not a compromise. It is what happens when a stone’s price reflects the cost of producing it rather than the cost of controlling how much of it reaches the market.
What most people do with the difference is instructive. They do not buy a tenth of a ring. They buy the ring they actually wanted — the carat weight they had in their head, the setting they liked rather than the one they could stretch to — and keep the rest for the wedding, or the deposit, or the year off.
