Sold individually.  Size and shape may vary.  Black Tourmaline (also known as Schorl) is classified as a semi-precious stone and is a protective stone which repels and blocks negative energies and psychic attack. 
 
 
Black Tourmaline is one of the most powerful crystals for protection and elimination of negative energy. It also helps to absorb any electromagnetic energy, so make sure you keep a piece of Black Tourmaline next to your computer. It is also one of the best crystals for anxiety.