# CZ's vs. diamonds **URL:** \ **Category:** Factual Questions\ **Created:** [August 8, 2001, 2:14am UTC](https://boards.straightdope.com/t/czs-vs-diamonds/75393 "2001-08-08T02:14:52Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![El\_Zagna](https://avatars.discourse-cdn.com/v4/letter/e/d2c977/32.png) [@El\_Zagna](https://boards.straightdope.com/u/El_Zagna)\ **Post date:** [August 8, 2001, 2:14am UTC](https://boards.straightdope.com/t/czs-vs-diamonds/75393/1 "2001-08-08T02:14:52Z")
A thread over in GD got me to ask a question that has been on my mind for a long time. Can the untrained eye tell the difference between a cubic zirconium and a real diamond? ---
**Author:** ![samclem](https://avatars.discourse-cdn.com/v4/letter/s/a9a28c/32.png) [@samclem](https://boards.straightdope.com/u/samclem)\ **Post date:** [August 8, 2001, 2:18am UTC](https://boards.straightdope.com/t/czs-vs-diamonds/75393/2 "2001-08-08T02:18:55Z")
“Untrained?” Probably not. Trained. For sure. Kinda educated, maybe. And, as a professional, I can tell you that I have seen CZ’s that would “almost” fool my eye(but not my diamond tester). But they are few and far between.’ I have seen “ugly” poorly cut diamonds that, if they were super clean inside, would have made me think they were CZ’s. ---
**Author:** ![El\_Zagna](https://avatars.discourse-cdn.com/v4/letter/e/d2c977/32.png) [@El\_Zagna](https://boards.straightdope.com/u/El_Zagna)\ **Post date:** [August 8, 2001, 2:52am UTC](https://boards.straightdope.com/t/czs-vs-diamonds/75393/3 "2001-08-08T02:52:08Z")
Sam - So what is it that you look for? I have heard that real diamonds have more “fire”, but I’ve also heard the same for CZ’s. ---
**Author:** ![samclem](https://avatars.discourse-cdn.com/v4/letter/s/a9a28c/32.png) [@samclem](https://boards.straightdope.com/u/samclem)\ **Post date:** [August 8, 2001, 3:16am UTC](https://boards.straightdope.com/t/czs-vs-diamonds/75393/4 "2001-08-08T03:16:28Z")
NO way to tell you. CZ’s are usually totally flawless, even under a 10x glass. But MOST of them have “lack of fire.” You’d have to look at a few 100-1000 diamonds, and 10-100 CZ’s, and it might make sense. There are certainly some that are foolers at first glance. CZ’s, when worn, become “abraided” on their edges/facets, whereas, diamonds don’t. This is quickly discernible under 10X magnification. ---
**Author:** ![Gaudere](https://avatars.discourse-cdn.com/v4/letter/g/e495f1/32.png) [@Gaudere](https://boards.straightdope.com/u/Gaudere)\ **Post date:** [August 8, 2001, 7:12am UTC](https://boards.straightdope.com/t/czs-vs-diamonds/75393/5 "2001-08-08T07:12:56Z")
CZs tend to fluoresce more, in my experience–in particular a blue-purple flash. They also may have bubble flaws, which are quite rare in diamonds, and do not have the marked flaws that natural diamonds may have, and are almost never less than superior in color and clarity, and I cannot imagine one that has inclusions of another stone (as diamonds sometimes do) unless you’re going out of your way to trick someone. Tho’ samclem says an inferior cut diamond could be mistaken for a CZ, those I have seen have very uniform proportions and faceting, but may just be less _carefully_ cut than a diamond. Since diamonds are expensive, cutters want to maximize every point, so a stone may be cut shallow or deep or slightly cockeyed to compensate for the flaws and shape of the natural rough. Since CZ rough is so cheap, there is no need to go to such lengths. CZs are also more likely, IME, to have polished girdles (the line between the top and the point bottom of the stone) than diamonds, but that again is likely a product of their mass production vs. the personal attention most decent diamonds get. With the right experience _and_ equipment, you can tell. Just eyeballing it, if you know what you’re doing, will give you a good guess unless someone has a particuarly tricky CZ. Most CZs I have seen have not been in circulation long enough to become abraded, and they’re not _that_ much softer than diamonds. Even diamonds will chip at the edges if struck the right way. CZs are about 75% heavier than a diamond of the same size, so you can sometimes tell by weight, but since you’re dealing with such small items you’d need very accurate measurements and a very accurate scale to be able to tell the difference. CZs are not the only simulated diamond used; mossainite, white spinel and white sapphire are still common, or becoming popular. YAGs and GGGs, synthetic white garnets, are no longer used, though my dad used to have a YAG around the store. ---
**Author:** ![samclem](https://avatars.discourse-cdn.com/v4/letter/s/a9a28c/32.png) [@samclem](https://boards.straightdope.com/u/samclem)\ **Post date:** [August 9, 2001, 2:15am UTC](https://boards.straightdope.com/t/czs-vs-diamonds/75393/6 "2001-08-09T02:15:47Z")
**Gaudere** good post. I agree with you almost 100% Again, CZ’s usually are too clean inside. But they seldom have the “fire” of a diamond. I will investigate in the next few days whether CZ’s have polished girdles more than diamonds. We certainly have enough to tell. I guess we see a lot of “circulated” CZ’s, usually mounted in a real gold band, as we live close to a promoter of this kind of item. Wear 'em for a month and they get abraded. As to telling by weight, most of the CZ’s that come into our store are mounted in rings. So their weight is not ascernible. ---
**Author:** ![John\_Thurner](https://avatars.discourse-cdn.com/v4/letter/j/ea666f/32.png) [@John\_Thurner](https://boards.straightdope.com/u/John_Thurner)\ **Post date:** [August 9, 2001, 3:28am UTC](https://boards.straightdope.com/t/czs-vs-diamonds/75393/7 "2001-08-09T03:28:16Z")
I know all of you will cringe at my suggestion, but you all forgot to mention the scratch test. Take a known CZ, and if it can scratch the unknown stone, the unknown is also a CZ. If not, it’s diamond. Of course, I’m going by a very basic gemmology course given in a larger metal-smithing program, so that might have problems I don’t know about. But it’s really the easiest way to be certain as far as I know. ---
**Author:** ![John\_Thurner](https://avatars.discourse-cdn.com/v4/letter/j/ea666f/32.png) [@John\_Thurner](https://boards.straightdope.com/u/John_Thurner)\ **Post date:** [August 9, 2001, 3:30am UTC](https://boards.straightdope.com/t/czs-vs-diamonds/75393/8 "2001-08-09T03:30:30Z")
Oh, and make sure to scratch along the girdle where it won’t be noticeable. Because even if it is just a CZ, you still won’t want to ruin the stone. ---
**Author:** ![DanBlather](https://avatars.discourse-cdn.com/v4/letter/d/f4b2a3/32.png) [@DanBlather](https://boards.straightdope.com/u/DanBlather)\ **Post date:** [August 9, 2001, 6:26am UTC](https://boards.straightdope.com/t/czs-vs-diamonds/75393/9 "2001-08-09T06:26:18Z")
I was looking at biggish CZs to replace the tiny diamond in my wife’s ring, but they didn’t look “right”. One problem was the cost. I don’t think that there is an incentive to do a good job cutting the CZ when they are so cheap.