Black tourmaline is a mineral that is formed in igneous and metamorphic rocks, particularly in granite and schist. It is a complex borosilicate mineral that contains various elements, including iron, aluminum, magnesium, and lithium. The formation process involves the crystallization of magma or the metamorphism of existing rocks under high pressure and temperature conditions. As the rocks cool, the black tourmaline crystals form in fractures and cavities within the rocks, often in association with other minerals such as quartz and feldspar.

Black tourmaline is believed to have a variety of metaphysical properties. It is considered a powerful grounding stone, helping to balance and stabilize energy within the body. It is also said to offer protection from negative energies, including electromagnetic radiation, psychic attacks, and negative thoughts.