Never clean emeralds in an ultrasonic cleaner or with soap. Some emeralds, especially those found in antique jewelry, are oiled using a green-colored oil are filled with an epoxy resin to hide flaws. Ultrasonic cleaning will remove oils and fillers, thereby exposing perhaps a paler or more flawed emerald.

Should this happen to you, the emerald can be reoiled as needed. Ionic cleaners are safe to use for emeralds and other jewelry.