The Emerald Gemstone is a 7.5 - 8 on the Moh's Scale of Hardness. It is a good gemstone for use in rings, pendants and earrings. Clean your Emerald with a soft, dry cloth. Avoid sudden temperature changes, household chemicals, and avoid ultrasonic jewelery cleaners. Emerald is often treated with oil to fill fissures and fractures as are characteristic to the gem.
You should NEVER clean an emerald in an ultrasonic cleaner, because this oil could be removed or damaged, making the fissures more visible. In addition, do not clean an Emerald in hot soapy water, since this too may remove this oil.