Black Tourmaline CrystalSemi polished Black Tourmaline Point. An energetic semi polished natural Black Tourmaline crystal. Black Tourmaline is the first choice for protection from radiation and electromagnetic fields (EMFs). The flat base makes it perfect to put in front of electrical devices or in rooms to help shield us from the many frequencies we are constantly bombarded with mobile phone towers, routers, TV signals, computers, radio waves and smart meters to name a few.