click to hear magnets sing
Separate this pair of hematite magnets, toss in the air and they will create an amazing sound as they attract, repel and finally connect. They are really strong as you'll see if you put them next to anything magnetic. Bonus: Impress your friends by placing one on each side of your palm... they'll stay attached!

Searchable (under many names: "singing magnets, "chatter stones," "magna buzz," "buzzing hematite magnets," "rattlesnake egg magnets" to name a few!) on the internet.