How do you tell the difference between diamonds, cubic zirconia, etc.?

January 15, 2017 4:57 PM

How can I lean to tell the difference between cubic zirconia, diamond, and other stones? According to my internet research, cubic zirconia has more "dispersiveness" and "fire" than diamond, but diamonds have more "brilliance" than cubic zirconia. Can I train my eye to tell the stones apart with those properties? What does the "brilliance" look like, and how does that differ from "dispersiveness" and "fire"? Any other tips for differentiating stones used in jewelry would also be welcome. For example, if you have tips related to rubies, emeralds, or pearls, please share!
posted by mortaddams to Clothing, Beauty, & Fashion (6 answers total)

Best answer: The easiest tell between a diamond and a CZ is the thermal conductivity. Breath on a CZ and it will cloud over with condensation. A diamond will not.
posted by janell at 5:23 PM on January 15, 2017 [10 favorites]

Best answer: If you sort of rub real pearls across your teeth (don't "bite" it), it feels kind of rough and gritty. Fake pearls feel smooth.
posted by If only I had a penguin... at 5:53 PM on January 15, 2017 [4 favorites]

Best answer: I think that brilliance vs fire: diamonds and cubic zirconia absorb and transmit a different spectrum of light. In practice, diamonds reflect natural light as "white light" and intensely, given the same amount of input light. CZ tends to be more "sparkly" with a spectrum of wavelengths and less intensely, given the same amount of input light.

If you're interested, a whitepaper on the transmissivities of different diamonds/CZ.
posted by porpoise at 6:21 PM on January 15, 2017 [1 favorite]

Best answer: CZ is much denser than diamond, almost double. Zirconia has a specific gravity (density relative to water) of around 5.5-6, diamond is roughly 3.5. CZ stones have more heft to them.

It also means that CZ stones are smaller than diamonds for the same carat size. For example, a 1 carat round CZ stone is a little more than 5.25 mm across. A 1 carat diamond would be a little under 6.5 mm.
posted by bonehead at 10:55 PM on January 15, 2017

Best answer: I'm currently reading "Stoned" by Aja Raden. She says:

Is a diamond really any better than a cubic zirconia?

The natural response is "yes." But I can tell you, as a jeweler, that most jewelers can't tell them apart ... not outside of their settings, anyway. At first glance, it's always the cheap setting that gives away the CZ. If you were to set a CZ in an expensive setting, and set it well, I couldn't tell it from a diamond, not with 100 percent certainty, not without an electronic testing pen that would shoot a little bit of light into it and back, electronically reading the refractive index.

posted by purpleclover at 11:36 PM on January 15, 2017 [5 favorites]

That book looks great, purpleclover, thanks for posting it!
posted by fiercecupcake at 5:22 AM on January 16, 2017