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Black Tourmaline (Schorl) 
Source: Found throughout the world predominantly in Sri Lanka, Brazil, Africa, USA, Australia, Afghanistan, Italy, Germany and Madagascar
Chakra: Earth, protects all
Zodiac: Capricorn
General: Black Tourmaline is the most effective blocker of curses, psychic attack, and ill-wishing.  It protects against mobile phone emanations, electromagnetic disturbance, radiation, and negative energies of all kinds.  Wear around your neck or place between yourself and the source of electromagnetics.  Place point out from the body, it draws off negative energy and clears blockages.  Gridded around the house or open space, it affords protection on all levels.  Connecting with the base chakra, Black Tourmaline grounds energy and increases physical vitality, dispersing tension and stress.  Clearing negative thoughts, it promotes a laid-back attitude, encouraging objective neutrality with clear, rational thought processes.  It also instils a positive attitude no matter what the circumstances and stimulates altruism and practical creativity.
Beneficial For: Claimed to be beneficial for – Negative energies, debilitating disease, immune system, arthritis, pain relief, realigning spinal column, protection, detoxification, spinal adjustments, balancing male-female energy, paranoia, hand-eye co-ordination, assimilation and translation of coded information, bronchitis, emphysema, pleurisy, pneumonia, energy flow, and removal of blockages.1
Emotional Healing: Claimed to be beneficial for anxiety, stress, suicidal thoughts, self-harming, drug abuse, soothes panic attacks especially those caused by confined spaces, and fears of dentists and doctors. 
Practical Uses: Wear to protect you against moaners, whingers, complaining neighbours or emotional vampires who burden you with their problems but will take no action to remedy them.
Workplace: To repel electromagnetic negative energy this stone should be worn or kept close when using computers or other electronic equipment.  Also hold for a few minutes when you need to use all your concentration, or when you need to wake up your mind, such as first thing in the morning.2
References:
Judy Hall, “The Encyclopedia of Crystals”, Bounty Books, London, 2015
Cassandra Eason, “The Complete Crystal Handbook”, Sterling Publishing, New York, 2010