If your gems are looking lackluster you can revive them and get them looking like new by dropping them into a a bowl of warm water that has had  a few drops of dish liquid in it. Let this sit for about 15 minutes. Then scrub gently with a soft toothbrush. Rinse and dry. The soap will have dissolved any grease or oils so they will sparkle. This can be done to any type of jewelry EXCEPT pearls.