The white sands of Mykonos capture the imagination of beachgoers, but the black sands of San Francisco’s Ocean Beach can capture a magnet. Waves and currents have broken down iron ore in the local geology, mixing it with sand. The process gives some beaches in the area a dark dramatic look and causes many of the particles to convey iron’s ferromagnetic properties. In this hands-on exhibit at San Francisco’s Exploratorium, visitors can make bridges and other shapes out of the sand using the magnetic field created by two strong permanent magnets.
Credit: Craig Bettenhausen/C&EN
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