In the past, people believed if their diamond could scratch glass, then it was real. While this may be a damaging truth to genuine gems, many fake diamonds do as well. Over the years, the craftsmanship of a diamond simulant (notably cubic zirconia (CZ) selections) has been constructed to fool a variety of interested parties, including jewelers who use the naked eye as their guide towards authenticity. Today, there is a multitude of techniques that help individuals purchase genuine diamonds and not fall victim to extremely convincing fakes.

An important part of detecting a real diamond is to recognize the characteristics that make cubic zirconia both similar and different from genuine diamonds. For starters, CZ possesses a hardness of 8.3 on the Mohs scale compared to the diamond's hardness of 10. While CZ can come in colored or colorless versions like real diamonds, they are optically flawless, whereas a diamond always contains some sort of flaw or defect in their composition.

While trained gemologists are seasoned in the ways of detecting a simulated diamond, the untrained eye may also catch on to glaring inconsistencies. For example, the color of a CZ may display a gray tone when exposed to prolonged amounts of sunlight. In many cases, individuals prefer to run specific tests on their diamond to make sure it is real. They wish to verify authenticity by checking qualities, such as the weight, thermal conductivity, light dispersion, visual optics, refractive index, and level of fluorescence.

An array of diamond tests exists with some better suited for unmounted diamonds than ones placed in a setting. Below is a run-through of some of the most commonly used methods of diamond detection:

Some individuals have been able to detect cubic zirconia by marking their stone with a grease pencil or felt-tipped pen. Since natural diamonds attract grease and a CZ does not, a simulant will repel grease. The transparency of a stone is also helpful. If you are able to turn over your gem and read through it after placing it over newsprint, chances are you do not possess a real diamond. It is important to know that this test is not 100% reliable, as some real diamonds are cut shallow and will fail this test.

The facet edges of a stone also establish authenticity. A cubic zirconia often showcases chipping or slightly rounded edges. When the edges of a stone are not sharp, you may suspect that your gem is not a real diamond.

With the "fog test," one may create fog on their gem in the same manner they would a mirror. If the stone stays fogged for 2 to 4 seconds, you may have a CZ on your hands because a real diamond instantly disperses heat before you can indicate fog. The disadvantage with this test is that accumulated dirt and oil on a stone will affect reliability.

Some people use the "U.V. test" to weed out diamond impostors and prove the worth of their gem. A high percentage of diamonds produce the color blue when placed under a black light (ultra violet light). This is often a good test since 99% of all diamond simulants do not. Seeing a medium to strong blue color is a good indication that you possess a diamond. On the downside, it also proves the worth of your gem. Diamonds with blue fluorescence are sometimes 20% less in value than those that do not. Therefore, not seeing blue fluorescence doesn't necessarily mean the stone is a cubic zirconia, but instead, may indicate a diamond with higher value.

Carat or gram scales come in handy to authenticate a diamond by analyzing its weight. Cubic zirconia weighs about 1.7 times more than diamonds under the same dimension and shape conditions.

With the "loop test," visual characteristics of a diamond are analyzed through a magnifying lens to establish its true identity. One should look for the cuts of the diamond (facets), check the girdle (frosty and faceted means diamond, waxy and glossy means it is a fake), spot small cracks and pinpoints (characteristics of a diamond), and locate setting stamps. Stamps that show "10K, 14K, 18K, 585, 750, 900, 950, PT, Plat" increase the chances of possessing a real diamond because CZ is not often set in real gold or platinum.

Overall, it is important to know that not all the tests and techniques used to differentiate a CZ from a real diamond are 100% reliable and conclusive. Often times, a diamond that passes an assortment of tests with flying colors can be trusted as a natural diamond.