Diamond earrings become dirty through frequent wear. They pick up oil from your skin and hair, causing the metal to become worn and the stone to lose its luster. For mild build-up, try a home cleaning remedy to add a bit of shine back to your favorite pair of diamond earrings. For more intense grime, consider having your earrings professionally cleaned.
more at: http://www.wikihow.com/Clean-Diamond-Earrings