Tumbled Shungite (price is for one, intuitively chosen).

Shields from EMF. Grounds spiritual energy to bring it to the earth plane. Protects, calms, and relaxes.

Every stone does more than is listed here. The best way to choose is to use your intuition. Just because someone says a stone does or doesn't do something, doesn't make it true for you. I encourage you to use them as you feel called.