Tourmaline is often found is association with quartz and is a common inclusion. When black it makes a very powerful stone for personal energy protection: in other colours the quartz acts to strongly amplify and broadcast the tourmaline''s innate energies. Tourmalines can also be multi-coloured - bi-coloured ones having 2 colours present within / adjacent to each other; watermelon having a pink central core within a green outer layer. The latter ones make one of the very best crystals for working with the heart and high heart centres. Green and pink tourmalines are good with the heart; blue and indicolite good with the throat and 3rd eye; orange and red with the lower chakra centres. However the most frequently used tourmaline is black. This is a hugely useful crystal for grounding, balancing and in absorbing and clearing the energy field or negative EMFs - hence their usefulness next to the TV or computer.