In theory, you can distinguish a diamond simply by looking at it. No other gem has properties that exactly match a diamond’s. However, this becomes difficult when examining set stones. Often, you can’t see enough to make an accurate assessment. In addition, today’s simulants imitate diamond’s appearance much more closely.

Distinguishing Diamonds by Their Appearance

You can’t make a positive diamond identification with your eyes alone. Nevertheless, the following features will often tell you if a gem is a diamond or not. Gemologists must educate their eyes by looking at many gems. You won’t always be in your lab when presented with a prospective diamond.

Look for these features as you examine diamonds and other gemstones.


The ability to separate white light into rainbow hues, dispersion is one of diamond’s most endearing qualities. How much dispersion, or fire, you see from a gem depends on its optical properties and cut. Although not all diamonds show the same amount of fire, the majority behave within a limited range.

Other gems usually show much more or much less dispersion. As you become familiar with diamonds, you’ll learn to distinguish quickly gems that have too much dispersion, like cubic zirconia