Diamonds are subjected to all sorts of treatments in order to enhance their beauty. Popular treatments include high pressure/high temperature treatments as well as coatings. These treatments can give the diamond a slightly different color and hide imperfections on the surface and within the diamond itself. While that’s a plus for people looking to buy less-than-perfect diamond jewelry to save money, it’s a bit of a dilemma for jewelers who are trying to determine the natural grading of a diamond. If it has been treated, it is generally worth less than a natural, untreated, diamond of the same visual quality. Knowing how to quickly and accurately test diamonds for coatings can keep a jeweler and you from paying too much for a treated stone.

A Simple Test For Coatings

One way that you can test a diamond for a coating is to scratch the pavilion lightly with a pair of jeweler’s tweezers. Since diamond is one of the hardest minerals known to man, this light scratching should do no damage, if it’s truly a natural, uncoated, diamond. If it is coated, however, the scratches should show up under magnification with an overhead fluorescent light, when the diamond surface is tilted approximately 45 degrees to your sight level. Even at only 10x magnification, the scratch lines should be fairly easy to spot. You can try the same test with a darkfield light and the scratches won’t be visible, so make sure you use the overhead fluorescent when you look for coatings.

If Unsure Ask A Jeweler

This is just one simple test to determine a coating on a diamond. There are a number of other tests that a jeweler can perform, if you suspect that the diamond you have is not a natural stone with no enhancements. Many grading laboratories will comment on some types of enhancements and not others on their lab reports, so the absence of a comment doesn’t mean it hasn’t been treated in some way.