In this artwork, fine grains of magnetite, a natural form of magnetic ore, move in response to a powerful magnet rotating inside the stone. The particles line up, south pole to north pole, creating jagged spikes that swirl around the center of the bowl.
Push the sand around and watch it pull itself back together; hold a handful of sand at the bottom of the bowl and watch the sand dance in your hand.
The magnetite here was collected locally; in fact, navigational charts sometimes warn mariners of false magnetic readings from San Francisco's magnetite-peppered shores.
© The Exploratorium, 1996