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A Medicine Wheel is made of stones. There were about 20,000 medicine wheels in North America, before the Europeans came. Medicine wheels are places for energy and healing, teaching and understanding. They are used for times of reflecting on life, and for joyous celebrations.
The Medicine Wheel represents all of creation. all races of people, animals, birds, fish, insects, trees,and stones, the sun, moon and earth are in the circle of the medicine wheel. Each stone tells part of the story. The circle is all of the cycles of nature, day and night, seasons, moons, life cycles, and orbits of the moon and planets.
Another site: What is a Medicine Wheel?