In a small dish of earth, bury the stone for three days. Most of the time houseplants can be used for this. Put a toothpick or some sort of marker in the surface of the earth above where you’ve buried your stone, though, or you might never find it again. In addition, beware of using houseplant’s earth if the stone contains a lot of negative energy; it will be absorbed by the earth (which is why you’re using the earth to cleanse the stone), but it will in turn be absorbed from the earth into the houseplant, and the house is likely to die.