You may want to put them in a ceramic or earthenware bowl of dry sea salt or in the earth. Resonating sound - Purify your crystals with the resonating sound of a bell. You can cleanse a roomful of crystals by ringing the bell above them, but the best way is to purify crystals one at a time. Smudging - Burn a wedge of dried herbs, waving the smoke over and through the crystals. Clean seawater is another option.
Some people suggest leaving the container on a window ledge for three days before the full moon.
Earth burial - If you feel they are safe enough, you can bury your crystals in the ground. This is recommended particularly if they have been negatively influenced by someone. You may even want to give them back to the earth so they can rest and circulate in nature. Amethyst bed - Put your crystal in a bed of amethyst clusters. Mountain crystal bed - Put small stones on a bed of mountain crystal which cleans without needing cleaning itself.