The pendants are made of shungite, which is  is a powerful stone to shield you from the electromagnetic radiation given off by electrical equipment. Shungite has been studied extensively for the treatment of depression, trauma, and all sorts of mental/emotional problems. It is said to absorb and eliminate anything that is a health hazard to human life.

Please notice it is normal that shungite may contain few quantities of pyrite and leave some powder residue after touching.