Here you see a sculpture using small pebbles which I collected on the beach in Dieppe.
Of course, you can use larger pebbles and stones, but the larger the stone, the larger the magnet needs to be.
And the larger the magnet, the more you must be careful that they don't crash together! I used 46 pebbles, 134 mini magnets S-05-02-N52N
and 16 larger magnets S-05-08-N