Subject: black sand why does it not go rusty from the salt sea water

On a New Zealand sea shore I found black sand.  took it home and dried it out 
and put a magnet to it, the blk sand  attached itself to the magnet there for 
it must be steel  as it came from the sea shore why does it not go rusty from 
the salt in the sea

Re: black sand why does it not go rusty from the salt sea water