SILVER - is really a precious metal but I thought I would add it to this list because I use so much of it as an accent. Silver has been used as early as the fourth millennium B.C. It wasn't until the mining of it in America and Mexico, that the value attached to it fell so dramatically. When silver is combined with weaker healing crystals or stones, it intensifies their attributes, making them more powerful.(this is especially so for turquoise and coral) For stones that are too powerful for you, use silver as a filter to tone that stones energy down. Silver also encourages inner peace and has a calming effect. Silver will work on all chakras.