Can you tell a diamond is real by breathing on it?

THE ANSWER

Sort of. The fog test gives a rough clue but it is not reliable. Breathe on a diamond and the fog disappears almost instantly. Diamonds conduct heat very well. They disperse the moisture in about one second. Glass and cubic zirconia stay foggy for several seconds. But moissanite also clears quickly because it conducts heat well too. So the breath test cannot tell a diamond from moissanite. It only helps rule out glass or cheap fakes. For a real answer, you need a jeweller with proper testing equipment. The breath test is a party trick, not a reliable method.

NEXT STEP

Read the side-by-side stone comparison to understand the key differences, or browse lab-grown engagement rings if you are ready to start looking at real options.