Identifying Diamonds to Imitations

Diamonds have been a very desirable gemstone for millennia. The most common imitations are Cubic Zirconia and Moissanite. Cubic zirconia and moissanite are very difficult for a layman to differentiate from a diamond, they both look very similar to diamonds and have a similar brilliance.

How to identify an imitation

  • Diamonds are harder than any other material available. A simple scratch test gives usually a high degree of accuracy. It is possible to buy a diamond scratch pen with a sapphire (hardness 9) or borazon(hardness 9.75) needle and scratch the diamond to see if it leaves a mark. This method is usually not preferred as it can leave a mark on the diamond. When analyzing worn jewellery if you notice any wear and tear on the diamond you can be sure the stone is not a diamond. The lack of wear and tear is on itself not a proof that the stone is a diamond.
  • Density testing, the mass density of diamond is 3.51g/cm³ compared to 5.65g/cm³ for zirconia. Thus, a zirconia with the same dimensions as a 1ct diamond will weigh approximately 1.6ct.
  • Thermal conductivity, diamonds are the best thermal conductors on earth meaning that heat spreads extremely fast in a diamond. The presidium tester uses this feature of the diamond to identify if a stone is natural. With the needle it heats the diamond up to a certain temperature and identifies how long it takes for the diamond to cool down.
  • To identify a diamond from an imitation we can also keep in mind typical optical characteristics of diamonds, if you can see any naturals or other remnants of the rough diamond, typical diamond inclusions, graining, etc… you can also be sure you have a diamond in your hand. Synthetics usually have curved lines and air bubbles that are present in their structure
  • A clear visible point can be observed when looking at edges of facets of diamonds. In diamonds these edges will be perfectly straight due to the hardness of the material, in other stones you will usually identify that the edges are rounded.
  • The cold sensation. Due to the high thermal conductivity a diamond always feels colder than a simulant. This only lasts until the stone reaches body temperature.
  • The line test. This test is well known and very easily checked but only useful for round diamonds. To verify if a stone is a diamond draw a line on a piece of paper and set the diamond table down on the line. If the line stays visible the stone is not a diamond.
  • An experienced diamond trader can identify the difference in brilliance between a diamond and a simulant. This has to do with the refractive index of diamond. It has a particular brilliance that can be immediately identified.

Diamonds love grease, an easy way to test if a diamond is real is to put some grease on the table of the diamond, then stick it to glass window. If it sticks, it’s a diamond!