Say No to Crack has a neat article on the ten strangest vintage comic book ads. This one is Kryptonite Rocks:
This one never made sense to me. Be a friend to superman by buying Kryptnotastic rocks? Kids were supposed to buy them to keep the rocks out of the hands of villains. Makes a tiny bit of sense, but why wouldn’t the government just destroy them all or send them into space?
I convinced a couple kids on the school bus to buy them for protection in case Superman was exposed to red Kryptonite and came after them. They felt this was a logical reason, and received this upon ordering:
Painted green rocks - they lost 3 weeks allowance, I got a great laugh. Then they went back to arguing whether or not Superman would come out of retirement to raise the Titanic.