Agate, moonstone, or hematite all work well and also obsidian if you can charge it well.
I would try obsidian or hematite because its like a mirror that will “turn the tide” of gossip. Make sure you charge the stone with your intention. I also know that a binding spell works for these things.
Perhaps this will help it lists the metaphysical properties of different types of gemstones – http://www.birthday-horoscopes.net/metaphysical-gemstones.htm