How To Spot a Fake Diamond

So what do you look for before buying, and how can you test the stone after it is bought?
This article discusses the comparison between real and fake diamonds, and gives you some ideas on how to spot a fake diamond. A fake diamond should be referred to as a "diamond simulant", of which cubic zirconia is probably the best known. For those of you who are in the market for diamond jewelry, diamond simulants have their place in the jewelry business; they are a good inexpensive choice for earrings, pendants, and costume jewelry.  They can also be a good interim choice until you can afford the real thing.

But if you want the real thing, then how do you spot the fake or the simulant?

Before You Buy

Five things to look for before you buy:

  1. If the stone being described is referred to as a "________ diamond", then it actually must be a diamond. Synthetic diamonds, clarity enhanced diamonds, and fancy colored diamonds are diamonds.... fake diamonds aren't.
  2. If a "deal" on a diamond is too good to be true.... it probably is, just walk away. If it is such a good deal, it will be there tomorrow.
  3. Buy only from reputable jewelry shops. Lessen your chances of being duped into buying a phoney by actually choosing a jewelry shop that has a name. Reputable jewelry shops protect their business interests by delivering the actual goods. The chances of them risking their credibility for selling fakes are low.
  4. Inquire about the stone’s authenticity. Assess the knowledge of the jeweler who’s recommending the stone sale to you. Does he know what he is talking about? If he is suspicious and unsure, that’s a warning sign. Hold your wallet and take extra precautions with your dealings with him.
  5. Does the jewelry shop offer a diamond certificate? The Gemological Institute should authenticate genuine diamonds with a certificate. So when you purchase a diamond, ask for a GIA or AGS certificate, as these are the two useful grading certificates.

If You Have Already Bought

You have bought what you think is a diamond, how can you be sure that it is the real thing and not a fake?

Comparing Fake Diamonds with Real Diamonds

Diamond simulants and synthetics fool even experts when they are compared side by side with real diamonds. So if it is difficult for the experts do you stand a chance?

Fake diamonds have been around for hundreds of years. Before the advent of modern day material technology, fake diamonds were made out of glass, and often referred to as "paste". (The term was used because the glass had to be in a molten state with the consistency of pasta before it was pressed into the diamond shaped molds. There have been many other "fake diamonds" over the years and with the introduction of new synthetic materials, like zirconium and Moissanite,  it has become much harder to separate the real diamonds and the fakes.

Before you start to compare a potential fake diamond with the real thing, it is first necessary to define what constitutes a fake diamond. To be a true "fake", the impostor must be sold or represented as a "diamond" when it is actually a completely different material.  If the stone is described as a "_____ diamond" or a man-made diamond, or a lab created diamond, then assuming that the seller is reputable, it is a diamond.  Some people consider these as fakes, but in reality they are diamonds, they are just not naturally occurring diamonds.

When something looks like a diamond but is actually a different material (not carbon), then the correct term is "diamond simulant".  The most common type of diamond simulant is Cubic Zirconia, but more recently, Synthetic Moissanite has crates a near perfect diamond look alike, with material properties that are very similar to a real diamond. Both of these are can be difficult to distinguish from the real thing, even for experts.

How can you tell the difference when you compare what you think is a fake diamond with a real diamond? The best method is to test the properties of the stones. The table below compares some of the properties of diamond and the most common alternates or “fakes”.

Properties of Diamonds and Simulants
Type Hardness Specific Gravity Other Properties
Paste Diamond 5-6 2.4-4.2 Low thermal conductivity, used since 1700
Cubic Zirconia 8.5 5.80 Usually no inclusions, low thermal conductivity.
Use started in 1976 to present.
Moissanite 9.25 3.21 May have brown tint, resistant to heat, inclusions occur as fine white tubes, high thermal conductivity.
Use started in 1998 to present.
Diamond 10 3.52 Inclusions usually appear as black specks or fissures, very high thermal conductivity.
Earliest documented use in 1476 to present.


The Difference Between Fake Diamonds and a Real Diamonds


This is the easiest comparison criterion for identifying Cubic Zirconia. Cubic Zirconia has a much higher specific gravity than diamond, and so a stone of equal size will be 1.6 to 1.7 times heavier than a diamond.
Paste may be heavier or lighter depending on the composition, and so it can appear similar to diamond.
The specific gravity of Moisannite is virtually identical to diamond, and hence can easily be mistaken as such when comparing weight alone.


Paste diamonds may contains small air bubbles, which is a definite give-away.
Cubic Zirconia is usually very clear, with no inclusions or faults. If the diamond is being offered at what appears to be a low cost, then suspicions should be aroused.

Thermal Conductivity

Paste and Cubic Zirconia both have low thermal conductivity compared to diamond. Using a good quality thermal gem tester should allow you to pick these imposters from the group.

Other Signs to Look For

Look at the setting.  Diamonds are normally set in good quality gold (18ct) or platinum.  If the setting looks cheap or is silver or stainless steel, then its likely that it is not a diamond.

What Else Can you Do?

There are a number of techniques that are described on-line, but to be honest, the best way is to take the stone to a trained gemologist.

identifying and grading diamonds is a complex process which involves a great deal of knowledge and expertise. You should not use the information on this page to make decisions on the value or authenticity of any particular stone. If you are not sure, always consult with a reputable diamond professional.


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