Tourmaline is formed magmatically in acid plutonites, particularly in pegmatites, where it forms freely grown, large and many coloured crystals.
Tourmaline was probably already known in antiquity, but was always equated with other stones depending on its colour. It was not until the 18th century that it appeared as the 'stone of wisdom, that is clear and resistant to all vagaries of fate...' (Bernardus Caesius). According to Arabic traditions, tourmaline is a stone of the sun that strengthens the heart and protects from nightmares. Though less colourful than other varieties, black tourmaline (also known as schorl) is one of the most popular stones for spiritual purposes.
Spiritually black tourmaline is an ideal stone for psychic protection for anyone who works or lives in challenging places or circumstances. Carrying or meditating with one of these stones can help keep your auric field clear of imbalance, even in the presence of destructive energies. Black tourmaline crystals act like etheric vacuum cleaners, clearing the body and your surroundings of negativity and disharmony. In addition, where such influences are not a problem, this stone can provide high levels of purification which serve to elevate the consciousness.
Emotionally black tourmaline is a strong grounding stone that disperses tension and stress. It removes negativity and thus encourages happiness.
Mentally black tourmaline balances right and left hemispheres of the brain and transmutes negative thought processes into positive ones. Tourmaline assists in understanding yourself and others. It takes you deep into your inner being, promoting self-confidence and diminishing fear. Banishing any feeling of victimization, tourmaline attracts inspiration, compassion, tolerance and prosperity.
Physically black tourmaline defends against debilitating disease, strengthens the immune system, treats dyslexia and arthritis, provides pain relief, and realigns the spinal column. 
Cleanse black tourmaline regularly by placing under running water and allowing the stone to dry in sunlight.