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00:03:53
Join Exploratorium educator Ken Finn as he unlocks the mystery behind the black sand (a.k.a. magnetite) at Ocean Beach. This piece explores the origin of magnetite in the Sierra Nevada mountains, its journey down the Sacramento and San Joaquin rivers to the Bay, and the interesting physical properties of this mineral, plus some fun things you can do with it.

00:05:26
The ground under our San Franciscan feet is constantly on the move. Join Exploratorium educator Ken Finn as we visit some spots around town where exposed rocks reveal the tale of an active earth.