To re-cap from last time, a diamond simulant (a “fake” diamond) is NOT diamond. A simulant is something which resembles a diamond visually, but the physical properties are totally different (i.e. it is “simulating” being a diamond). They can be both natural or man-made substances.

Some common simulants include:

  • Cubic Zirconia
  • Moissanite
  • Glass
  • Plastic
  • Natural and synthetic spinel
  • Natural and synthetic sapphire
  • Yttrium Aluminium Garnet (“YAG”)
  • Gadolinium Gallium Garnet (“GGG”)


I thought it would be useful to give you some tips and tricks which will help you identify a simulant diamond. Unlike identifying a synthetic diamond (TBD in my next blog!) most of these are tests which you can do at home.


  1. Read Through Effect

Well proportioned simulants can display a “read-through” effect. This means that when you place the simulant over some written text, that text will be visible through the simulant. With natural diamond, the text would not be visible.


See my Instagram post for a video of this in action –


  1. Polish Quality

Diamond is a lot harder than simulants therefore it will take a high-quality polish producing very sharp facet junctions (i.e. the edges between each facet. Facets being the “faces” or “sides” of the stone). Due to their relative softness, simulants’ facet junctions appear more rounded, and in general, most simulants quickly show signs of wear, with scratches and visible markings.


See my Instagram post for an example of a cubic zirconia with low polish quality –


  1. Blue Flashes

When light enters a diamond, it is “refracted” within the stone and then “reflected” out of the stone. “Fire” (often also called sparkle) is the name of the flashes of colour that you see coming out of the diamond as a result of this refraction and reflection. Some simulants have a much higher dispersion rate than diamonds so they will show significantly more fire. This often manifests as lots of deep blue and purple flashes. You will still get flashes of these colours in a natural diamond, but they will be far fewer.


To see what I mean by these deep blue/purple flashes have a look at my Instagram video –


  1. Doubling

If you look at some diamond simulants under magnification, you will see “doubling” of the facet junctions i.e. you’ll see two edges when in reality there is only one (a bit like when you’ve had one too many drinks…!). This will not happen with natural diamond…unless you have indeed had one too many drinks!


  1. Weight

Diamonds and simulants have very different masses and therefore a simulant which has the exact same mm dimensions as a diamond could have a very different weight!


To see an example of this, have a look at my Instagram video –


  1. Thermal Diamond Tester

Diamond has very high “thermal conductivity” (that is, it transfers heat easily), so we can use a clever piece of kit called a Thermal Diamond Tester to identify natural diamond. The tester has a little probe which you place on the stone, and within seconds the machine will tell you if it is a natural diamond or not! Usually with a big beep!


To see the Thermal Diamond Tester in action, have a look at my Instagram video –


It’s important to note that these methods are not fail safe! If you are really unsure about whether your stone is a diamond, take it to your local jeweller and they will be able to tell you straight away, failing that, come and visit us at Celsteel!