Black Tourmaline is a stone of  protection. It works through clearing the emotional consciousness. It also aids in focusing on new goals and in the development of new ideas. Black tourmaline absorbs negativity/low vibrating frequencies and grounds them, so that these frequencies cannot cause any harm. This crystal also absorbs electromagnetic frequency radiation (EMF smog- harmful radiation that often comes from electronics such as cell phones, computers, radios, etc.)
(this listing is for one raw/rough Black Tourmaline crystal, and is approximately 3/4"-1" in size)