Distinuishing Simulants from the Real Thing

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Jun 4, 2002
I keep reading that some simulants are so good that even experts have difficulty telling them apart from real diamonds.

So how can experts tell them apart? Is it a matter of looking for something specific? Or is it something very subtle that only comes after looking at thousands of different stones? Do you need some sort of device to tell?

I saw the suggestion in one article that you should put a stone on a black background, and if you see a lot of black showing through, then its a simulant. But I've learned from my research that this is no foolproof test, as a lot of black would show through in a poorly cut diamond, and the index of refraction of CZ is high enough that very little black would show through for a well cut CZ.

Thanks for any advice!


Jun 4, 2002
I know the real dealers and pawn shops test with a device that runs an electrical current through the stone, checking whether its a diamond or moissanite, which is one of the best substitutes out there. Also, another clear test to tell whether its a diamond or moissanite is that moissanite is doubly refractive of colored light, so you'll see much more color come off of it. Other than that test, from basic tests, its hard to near impossible to tell whether its a moissanite or a diamond. Oh yeah, another thing is if you're checking the loose stones, moissanite will float while CZ and diamond sink? Correct me if I'm wrong but I believe thats how it goes.

Anyways, if you want more tests, I suggest you search in this forum. I believe theres another thread dealing with this.


Sep 3, 2000
Yttrium stabilizied CZ cut to ideal specs, such as the Van Graff and several other brands, look very much like diamonds face-up. Even these excellent simulants do not mechancially test or look like the real thing from the side or back.

There is a difference and experts are equipped to tell either visually or with small machines that thermal conductance rates or electronic conductance.

Simulants have a definite place in the market. The good ones stand out a great deal from the cheap CZ stones that never look like diamonds.

Moissanite is far from cheap and also does not look like a diamond. At least, not to me. Just because it equires a different test device does not mean much as I can tell a Moissanite without a device, only with a loupe.
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