Stones
I first was formally introduced to the power of stones in a course I took at the Aletheia Psycho-Physical Foundation entitled Lythotherapy. Jack Schwarz explained basically that part of the reason a particular stone effects a person is because of the elements in a particular stone will resonate with a particular chakra, or organ in a person. The effect of stones are similar to ideas of homeopathy.
When I was in the border town of Mae Sai, Thailand I met a Burmese man who had set up a shop with his semi precious stones. He was very knowledgeable about stones and showed me some of his collection as well as briefly demonstrated how the stones are ground and polished.