• JFile: :read: Unable to open file:
  • JFile: :read: Unable to open file: /home/ronab886/public_html/components/com_jsn/assets/js/socialconnect.min.js?v=2.3.3
5 ways not to spot a fake diamond

5 ways not to spot a fake diamond

An article recently appeared in Business Insider entitled ‘5 ways to spot a fake diamond’. In this article, a 20th Century Decorative Arts expert discussed the ways to distinguish between a real diamond and a simulant (something that looks like a diamond but isn’t one), giving 5 ‘easy ways’ to tell if the stone you have is actually a diamond.

Sounds great hey?  

The only problem is that each part of the author’s 5 step plan is almost as flawed as a Pique 3 diamond. Let’s have a look at these points in turn.


A Pique 3 diamond - the imperfections severely compromise the beauty and durability of this gemstone.  Image copyright J Griffiths.

Step 1 - Look at the diamond and setting through a loupe.

A 10x loupe is the most valuable tool in any gemmologist’s arsenal. Well nearly. The eye and the brain are actually the most important tools they have. A well-trained and informed gemmologist can pick up details that a newcomer misses.  

The article states: “A fake stone would be perfect – absolutely perfect”. The problem is, diamonds may look absolutely perfect too! This is why we have the ‘Flawless’ grade.  

The reader is then advised to look at the diamonds edges, noting that a real stone will have sharp edges and a fake one will have rounded edges. And yes, for the most part, a diamond’s absolute hardness means that they will take and retain a fabulously sharp facet edge. But what if the stone had been rattling around in a jewellery box with other diamonds for the last 50+ years? As a result of poor treatment, even a diamond may have damaged facet edges that appear to be rounded. 


A diamond showing sharp facet edges, an abraded sapphire, and the rounded edges of a cubic zirconia.  Images copyright Gem-A.

And what about this setting the stone in a precious metal? Over 10 years of working in the industry, I have seen diamonds set in all manner of strange materials. Going further back in time, platinum only appeared in jewellery on a regular basis from around 1890. Until that date, if you wanted to increase the white appearance of your stones, the only metal option was silver. We didn’t start making white gold until WW2.

Step 2 - Rub sandpaper against the stone.


This is a terrible piece of advice! In gemmology school, we talk about working with hardness ‘pencils’ (sticks tipped with a crystal point) and utilising scratch testing. We emphasise that this is a last resort option, and that one should work from softest through to hardest. We also make it absolutely clear, that as a destructive test method, this should be done under magnification, on a small, unnoticeable part of the gem under test.

By using sandpaper, you have thousands of tiny crystal grains pointing in random directions. Instead of one crystal, you have thousands potentially scratching your stone. 

The bigger issue here is that the author doesn’t go into what the sandpaper is made of. There are diamond sandpapers are available on the market. These sheets are impregnated with industrial diamonds (the ones not pretty enough to make it to jewels). Given that diamond can cut diamond, this sandpaper is always going to scratch everything.  


Step 3 - Do the fog test.

This rather vague test relies on the high thermal conductivity of a diamond. And yes, a diamond will wick heat away from something much faster than many of its simulants. BUT. If you breathe hot air on a diamond, you are also breathing out moisture. As a result of this, water droplets cling to the surface of the stone and give a fogged appearance.  

We use this quality when working out the colour of a diamond. Because we get distracted by the lustre of the stone (how shiny it is), we ‘huff’ on the diamond to reduce the reflection of light so that we can see the actual colour of it more clearly.

Step 4 - Hold it in the light and see how it sparkles.

You know what, this isn’t a bad idea.  

It’s kind of what all gemmologists actually do with gemstones. The only problem is that the explanation of what light does inside the diamond is wrong. When light enters a diamond, it returns to the eye as brilliance and fire. Brilliance is the white light (as is correctly stated). But fire (rainbow light) is something that happens inside the stone as well, so you will see both white light and rainbow coloured light inside a real diamond. Quite the opposite of what the article claims.


A diamond showing appreciable fire.  Image copyright Gem-A.

Granted, a number of diamond simulants show much more fire than a diamond does. In the case of synthetic moissanite, you’ll see nearly 3 times as much. It’s a flashy looking stone.  

Step 5 - Look at the stone’s refractivity.

Refraction is the slowing and apparent bending of light as it enters a more optically dense material. We’ve all seen it when the straw in our G&T seems to bend in the glass. 


A drink showing the bending effect of light on the appearance of the straw. A G&T was severely damaged in the making of this image.

And yes, the spot or line test does work. But only for a loose, well-cut, modern round brilliant. If you were to try this test on any other cut of diamond, or even on one of the early round cuts manufactured before 1919 (when Marcel Tolkowsky revolutionised diamond cutting) then even the diamond will fail the test.  


So to summarise, yes. There are lots of ways of identifying diamonds. But it takes time to learn them and there’s a lot more to it than meets the eye.  

Sadly, there is a lot of confusion and misunderstanding in the world about some of our most valuable, precious, and downright pretty resources. If in doubt, speak to an expert. If you would like to learn even more, come and talk to me or to my colleagues at Gem-A and we’ll gladly teach you how to identify diamonds and many, many more gemstones.  

Whatever you do, stay away from the sandpaper. 

Facebook Twitter Google+ Pinterest LinkedIn

Leave a comment


Log in

fb iconLog in with Facebook

Get Your Sparkle Fix

Sign up to get the latest Shiny Pretty news, info,
offers & more


Check out our Privacy Policy & Terms of use
You can unsubscribe from email list at any time