Jump to content

How can you tell if a diamond is real


Recommended Posts

Easiest and most reliable way to tell is to ask a jeweler. Most will do this for free if you take the diamond into the store.


Whatever you do, do not attempt to scratch glass with your diamond as it may damage the diamond (even if real). Also, do not strike a diamond -- it will shatter!!

Link to comment
Share on other sites

  • 7 years later...

I heard there are quite a few things you can do to say a real one from a fake diamond.

  • Weight test (glass weights more than diamond)
  • Scratch test (diamonds scratch glass)
  • Breath test (diamonds keep no vapor)
  • Clarity test (you cannot read through a real diamond)

I think all these should help identify if a diamond is real. Other than that, it is good to be able to understand things like diamond clarity, color, cut, carat etc. For this, you can check out many pages on the Internet such as this one:


(link deleted by moderator)



Edited by hermann
Link to comment
Share on other sites

I'm not sure that reviving a 6 year old thread is worth it, considering it looks like gratuitous advertising for a vendor. In any case, all of the tests you mention above are relatively unreliable (some more so than others), and asking a jewellery professional is by far the easiest way.

Link to comment
Share on other sites

This is really bad advice from Ginger above ( in addition to spam) but it's an important and common question so I'll chime in anyway.


First to Ginger's list.


•Weight test (glass weights more than diamond)


Glass usually is about the same density as diamond. CZ is quite a bit heavier. In practical terms though, most gems are pretty light and it takes both a decent scale and a good reference for what it ‘should’ weigh to tell if it’s different. The 'heft' of a 1/2 carat and 3/4 carat are 50% different but it's still so small that you can't reallly use it as a separation method without taking careful measurements and a decent scale. For 99% of the population this makes it a useless test.


•Scratch test (diamonds scratch glass)


It’s true that diamonds scratch glass. Then again, so do CZ’s, Moissanite, sapphire and most of the other substitutes that you’re trying to separate. This does no good at all.



•Breath test (diamonds keep no vapor)

As with #1 above, this is basically correct but not very useful. You can’t really fog a diamond in the same way that you fog a mirror. It dissipates much more quickly than CZ and glass, which are the usual substitutes. The problem is that it takes a reference for what to expect and most people don’t have this benchmark and it’s pretty hard to do on very small stones.



•Clarity test (you cannot read through a real diamond)


You can’t read through most of the fakes either. To make it worse, if a diamond is badly enough cut you actually can see through it. This is the test that Jan is discussing above and it's correct that, upside down, diamonds look a bit different from CZ's but without a reference it's very difficult to explain what that difference is. Obviously this only works on unmounted stones. If you practice a bit, this is a helpful test but it's another one that doesn't apply for the majority of people and can't be used the majority of the time.



OK, so how DO you do it?


For gemologists, gem ID is a matter of accumulating evidence. Sometimes it's easy and sometimes it's a chore. There’s not usually a decisive test that doesn’t involve a certain amount of tools but there are some clues to look for on suspected diamonds are pretty easy. You’re not trying to make a positive ID, you’re trying to separate ‘probably a diamond’ from ‘probably not a diamond’ with a quick and dirty test. If you need a decisive answer, seek out a pro.


You’ll notice that most of the pro’s start and often end with a thermal and/or electrical probe. They cost about $100 and take about 5 seconds to do. I absolutely agree with the above that simply going to a pro who has one of these is by far the easiest and most reliable method for individuals to identify diamonds. Diamonds conduct heat and electricity differently than the substitutes and these tools are designed to spot that difference. If you’ve got one you already know this and if you don’t’ I would go out and buy one unless you're planning on getting into the business.



That said, here are a few more clues to look for:


Color. Nearly all substitutes that you come across are cubic zirconia or CZ and most CZs are really white. Most diamonds have a hint of color to them. 'D' color is a red flag but, more importantly, an 'L' color is a clue towards diamond.


Condition. CZ’s wear differently than diamonds. If a CZ is something other than brand new, you’ll usually see minor chipping around the edge of the table, the star facets, the girdle, etc. Glass wears even faster. You’ll often see scratches on the table and similar signs of wear on the fakes that aren't present in diamonds. If the mounting has significant wear and the stone is still perfect, that points towards diamond. If there's significant wear to the stone, especially if the mounting looks nearly new, that points towards a fake.


Context. Usually the mountings are different. If the quality of the materials or the craftsmanship of the setting seem out of line with the stone, that’s a bad sign. For example, 3 carat VVS diamonds are rarely set in 10k.


Inclusions. CZ’s are basically flawless. Diamonds almost always have inclusions. Look for crystals, feathers, spots, etc. Sometimes you can get tripped up by dirt or damage but there are certain inclusions that appear in diamond that NEVER are present in CZ's or glass. If it's absolutely clean, that points towards a fake, if it's full of junk, that points towards diamond. Mineral inclusions at the least rule out CZ as an option.


Symmetry. CZ’s are cut by machines and are usually pretty darned symmetrical. Diamonds are hand cut and often have minor variations if you look for details. Extra facets, naturals, unusually large or small tables, tall crowns, culets, out of round, off-center table or culet, etc. Old European cuts and out-of-square princess cut CZ’s are pretty rare for example.


Girdle treatments. There are several different ways the girdle on a diamond can be finished and rather few of them really look like the way CZ’s are finished. I don’t recall ever seeing a CZ with a faceted girdle for example. I suspect it could be done but the factories producing CZ by the ton don’t seem to do it so it’s an easy clue to look for.


Moissanite. Moissanite is doubly refractive. Look at the culet through one of the crown facets and you’ll see a doubling effect that is NEVER present in a diamond. It’s also a slightly ‘off’ color.

Edited by denverappraiser
  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...