A friend of mine wrote that she was having trouble with some sort of negative energy that possibly could be considered demonic, and she asked about some stones for this. I thought I’d share what I’d said in my email since protection questions come up quite often
“Black stones are very protective, so yes, I’d go with the black kyanite (which she already had). Black tourmaline would be my first choice, as it is said to transmute negative energy to positive, and be protective that way. There’s also a huge list here http://crystalsandjewelry.com/goodies/metaphysical/crystals/stones-by-use and you could surely find something you already have on it.
When I have an person bringing in negative energy like this, one thing I do is a ritual grid at home, and leave it in place until the negative energy has passed. I had one set up for almost 2 years to deal with a person I used to have to deal with, but in the end they freaked me out a little but nothing worse happened.
And of course, clear out your own energy field regularly throughout the day. Duck in the bathroom if need be. Taking less nasty around with you helps.”
Another point that she and I discussed elsewhere is that while black stones are protective, even black obsidians also have a tendency to bring things to the surface energetically. This can be super useful in most situations, to get something out and deal with it is best. Sometimes, though, it feels like too much or for some other reason you may not want it. In those cases, I’d avoid obsidians in favor of another protective stone, or program and ask the obsidian to avoid this type of energy.
And as always, arrange your activities so that you deal with the person in question’s negative energy as little as possible. Often a combination of that practical stuff and energetic boost together make for the best situation possible.