The following tests can help you determine if a stone is a real diamond, i.e. natural or lab-grown, or a fake diamond, i.e. moissanite, cubic zirconia, zircon, white topaz or white sapphire:
- Position the stone at the contact point of an electronic diamond tester. The tester does not react if the diamond is a fake; a beep sounds and an indicator lights up if the diamond is real.
- In a common heat test conducted by many jewelry stores, a fake diamond will heat up while a real diamond quickly disperses the heat.
- Cubic zirconia and other fake diamonds typically weigh from 40%-70% more than what a real diamond with the same “carat size” would weigh according to a gemstone size-weight chart.
- A fake diamond sends out a rainbow like effervescence while a real diamond emits a characteristic white shine, which is commonly called the diamond’s “brilliance.”
- Fog up the stone with your breath. On a real diamond, the fog will evaporate almost immediately. A fake diamond will fog up for 2-4 seconds the first time you breath out, and with each exhaled breath the stone fogs up more as condensation builds up.
- Check to see if your stone scratches by rubbing it on the surface of sandpaper. If the stone gets scratched, it is a fake. Caution: Do not attempt to bang against the stone with a hammer. While the surface of a real diamond cannot be scratched, it can be chipped.
- Turn a loose (un-mounted) stone upside down and place it on a newspaper. If you can read right through it, or even decipher distorted smudge marks from the newspaper print, the stone is a fake. However, take into account that a real diamond that is poorly cut, i.e. lacking proportion, will also enable you to read the newspaper through it.
- Real diamonds are flawed; fakes present an illusion of flawlessness, masking the fact that they are not real. Most real diamonds will show inclusions (internal imperfections) through a jeweler’s loupe or a 1200x microscope. Cubic zirconia, when fashioned to perfection, does not contain any inclusions. Lab-grown diamonds, which pass all the other tests, also lack the imperfections that are inherent in most natural diamonds.
- Place the stone under a UV light or a black light. A real diamond will reflect medium-dark blue fluorescence. This test is not conclusive as the absence of blue does not necessarily prove that the stone is a fake – it may just be a better quality diamond. Moissanite may reflect green, yellow or gray fluorescence under UV light.
- Ask your jeweler for a detailed certificate from a recognized independent gemological laboratory to authenticate the genuineness of your stone.