Diamond vs. CZ
October 20, 2009 11:39 AM   Subscribe

Can you tell the difference between a diamond and a cubic zirconia?

Have you ever looked at a diamond and a cubic zirconia (same size and cut) side by side and could definitively could tell them apart?

If a well cut CZ was placed in a precious metal setting is there any way that the average person could tell it was not a diamond?

Almost every article I've read seems to agree that it is nearly impossible to tell the difference between a diamond and CZ without some sort of test or 10x magnification. Yet, every girl I've ever asked said that it is easy to tell the difference between the two. I have a hunch they are comparing a fairly plain CZ without many cuts set in cheap costume jewelery to well cut/faceted diamonds set in expensive metals. Any first hand experience would be interesting.
posted by comatose to Science & Nature (25 answers total) 4 users marked this as a favorite
.....the average person? No, no there isn't.

Your girlfriend? In a heatbeat.
posted by Wilder at 11:44 AM on October 20, 2009 [5 favorites]

An easy way to tell the difference, if you're the girlfriend, is to ask yourself "Is this rock way the hell too big for Boyfriend to afford?"
posted by ROU_Xenophobe at 11:47 AM on October 20, 2009

A cubic zirconia actually has a lot more "flash" than a diamond typically does, kind of crossing the line from "pretty" to "gaudy."
posted by explosion at 11:47 AM on October 20, 2009 [2 favorites]

sorry to be flip!

I have seen a piece done exactly like a Tiffany ring as a kind of back-up piece when the lady in question did not want to wear her $13,000 ring when travelling abroad. What I did notice is it seemed to need more regular cleaning/shining up to maintain the pretence.

(This may be the cut which was a modified emerald cut, so not as many facets to sparkle but the setting was recreated exactly)
posted by Wilder at 11:49 AM on October 20, 2009

Apparently a simple way to distinguish cubic zirconia from diamond is to get a hold of a black light and shine it on the stone. Diamonds will usually glow blue, cubic zirconia will glow a dirty yellow.

Someone once told me a simple way to tell if a diamond is real or not is to try and scratch it with another diamond. If it's CZ, it'll scratch much more easily than a diamond. Of course, then you've ruined the stone.

Don't tell a girl it's a diamond if it's not. She'll find out, eventually.
posted by np312 at 12:01 PM on October 20, 2009

I CZ always feels warmer to the touch. To me anyway. And yeah, it's more brilliant and shiny.
posted by greta simone at 12:02 PM on October 20, 2009

I *think* CZ......
posted by greta simone at 12:03 PM on October 20, 2009

Wikipedia on this subject

Of the properties listed, it sounds like "every girl" could distinguish them based on dispersion, specific gravity, flaws and color. Flaws and color can be "fixed" (just include some of both). I don't know about dispersion. Density is going to be pretty hard to fake without it being apparent. But if the CZ is in a ring, it will be hard to measure.
posted by DU at 12:05 PM on October 20, 2009

According to this page
Another trick used to detect Cubic Zirconia from diamond is to mark the stone with a grease pencil or felt-tipped pen. Natural diamonds attract grease, while Cubic Zirconia repels grease. You can also Inspect the facet edges with a 10x loupe to look for any chipping or slightly rounded (not sharp) edges that are telltale signs of Cubic Zirconia.
One thing we did at the office here once was to put a pencil mark on a piece of paper and put with the loose stone on top of it, in CZ you will see a circle, and not on a diamond. I can't find the original page which discussed that though
posted by bottlebrushtree at 12:14 PM on October 20, 2009

Best answer: The center stone on my wife's engagement ring fell out one day while she was working at our co-op preschool. Not having the money to blow on a new stone, we had it replaced with a CZ of an identical size and cut. It was indistinguishable from the original, but of course we didn't shine blacklights on it or anything.
posted by Xoebe at 12:15 PM on October 20, 2009

Cheap CZs look like mass-produced chunks of glass, which they are, and are usually set in a lower-quality setting. I suspect when someone says "anyone can tell" they are referring to lower-quality, machine-stamped CZs, not hand-cut CZs in an expensive setting, but I am not a diamond-expert.

I have heard that a CZ will hold the fog from your breath, which a diamond won't.
posted by crush-onastick at 12:20 PM on October 20, 2009

Not sure if one can tell with the naked eye but most women want their rings insured. Then the jig will be up.

We found out that the ring my ex bought me was a crappy piece (still not 100% if it was fake) that looked good on the finger but value estimation proved it was junk. Part of me was angry for the ex--he totally got taken by a mall, chain jewelry store. The platinum band was worth far more and that is what my husband used as partial down payment from his broker aunt. Now I have a real ring that I always get compliments on.

Good luck and be honest. If you can't afford a diamond but want to marry, tell her. Then get one when you can down the road.
posted by stormpooper at 12:25 PM on October 20, 2009

Consider also the entire presentation of the stone. You are unlikely to see CZs in a well made, expensive setting.

No, more likely, the setting will look cheap, too, because people buying CZ's don't have money to spend on the setting, either. The women that claim they can always spot CZs are likely getting tipped off by a low-quality setting as much as the stone itself. They can't quite put their finger on why they know it's a CZ; they just know.
posted by Cool Papa Bell at 12:35 PM on October 20, 2009

I can't tell if you're asking because you're simply curious or whether you're considering buying a ring and want alternatives to diamond. If the latter, don't neglect moissanite. On the Mohs hardness scale, cubic zirconia is 8.3, moissanite is 9.25, and diamond is 10. That means it's not quite as hard as diamond but it's still harder that most all other minerals (e.g. sapphire is 9.0) and should easily cut glass just like diamond. According to the linked article it's about a tenth as costly as diamond and even skilled jewelers cannot tell the two apart.
posted by Rhomboid at 1:03 PM on October 20, 2009 [1 favorite]

Oh and whatever you decide, make sure you disclose your choice to the ring's recipient. I don't think anyone's advice in this thread should be construed as license to deceive.
posted by Rhomboid at 1:06 PM on October 20, 2009

I've also heard if you sprinkle water on the stone, on CZ the water will sheet, on a diamond it will bead.
posted by Acacia at 1:15 PM on October 20, 2009

Response by poster: I am really just curious if you can tell the difference by looking at them, not what kind of "tests" might be able to distinguish between the two.
posted by comatose at 1:42 PM on October 20, 2009

Best answer: Cheap CZ is horrible, and looks too blue and without the fire of diamond. A top-grade CZ, though, is a whole different story.

There's a jeweller near my office that sells nothing but top-grade CZ jewellery, in beautiful, classic (i.e. copy) settings. One lunchtime I was browsing in there and a man came in with the classic Tiffany blue box. Inside was a genuine 2ct classic Tiffany round-cut solitaire diamond engagement ring, probably £25,000. He wanted an identical CZ ring, so he could take the diamond back to Tiffany and get a refund under the 30-day returns policy and propose to his girlfriend with the fake, costing £300, making her think she was getting the real thing. The store had to order in the correct sized ring but I stood at the counter as he and the assistant compared the genuine ring with the display copy and you couldn't tell the difference with the naked eye.

After he'd left the sales assistant told me that, since the credit crunch, they'd done a ton of business with people looking either to buy a fake instead of a diamond or to get a replica for a diamond they were intending to return, like that guy.
posted by essexjan at 2:26 PM on October 20, 2009 [2 favorites]

Is there a good place/recommended place in the US or in Colorado
that sells high quality top grade CZ?
posted by digividal at 2:59 PM on October 20, 2009

Best answer: Side by side, yes I could tell (my first engagement ring was a CZ which I wore while we shopped for my second, sapphire, engagement ring). For me, the difference had something to do with the colors reflected by the two stones. The diamond was much more colorful than the CZ (someone above called it "fire" - the CZ had less fire). And yes, the CZ dulled pretty quickly (although shined right up when I cleaned it). Fog test works, too :)
posted by echo0720 at 4:52 PM on October 20, 2009

Best answer: An attorney I worked with had a pin made for herself that was a 'scales of justice' theme. In each scale, there was a sparkly gem - one was diamond, the other CZ. At a glance, they were indistinguishable but once one stopped and looked, the difference was rather obvious. The CZ lacked the depth of "fire" that the diamond had.

So, yeah, laypeople can tell the difference, even if the setting of the stones is identical.
posted by LOLAttorney2009 at 5:36 PM on October 20, 2009

There is a difference in refractive index of about 0.25, which means that two identically shaped shaped stones would look very different, though there is nothing stopping you from cutting CZ so that it has the same total internal reflection characteristics (the "sparkle") as diamond. However, the difference in dispersion, the amount by which it separates white light into separate colours, (the "fire") will still be noticeable.
posted by alby at 5:37 PM on October 20, 2009

Also, if the diamond/CZ is big enough the difference in temperature to the touch might be noticeable. Diamond is an extremely good conductor (thereby "sucking" the heat out of your hand and feeling cold) whereas CZ is an insulator.
posted by alby at 5:39 PM on October 20, 2009

I worked in the diamond business for 7 years, so I know I can easily spot the difference with my naked eye. To somebody completely untrained (typical guy), I could see how they wouldn't be able to tell the difference. But to somebody who's looked at a lot of diamonds with a lot of attention (typical women), it's pretty obvious.
posted by TruthAboutDiamonds at 7:03 AM on October 21, 2009

Look into Moissanite a.k.a. silicon carbide. It's nearly as hard as diamond on the moh scale and has the advantage of sparkling more than diamond because of a higher refractive index.

posted by robofunk at 9:31 AM on October 21, 2009

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