Now *that* is not what I was expecting! It must have some high ferrous content....but that would explain things. Andy.
Actually, magnetic sand is just sand with a high amount of the mineral called magnetite. Guess why it's called that!! Oh, and magnetite is black... Andy.
Did you manage to remove all of the black sand and fix the problem, though, George? Must be tough to get that off the neodymium magnets in the motor. Andy.