According to legend, anyone who takes black rock or sand from the Hawaiian islands will suffer until the native elements are returned. Research states that Pele considers the rock and sand her children, and punishes anyone who takes them with a streak of bad luck. Pele's Curse.
When I visited Hawaii in the 80's I wasn't aware of this legend. Having a small collection of shells at home, I thought it would be nice to bring back a small souvenir from the islands, so I brought back two small pieces of lava rock. Small mind you - no bigger than a nickel. Well, "bad luck" soon followed.
I never thought much of it - you know, things happen. But then my 9 month old cat got injured several times in a short time frame, and finally succumbed to an illness that she had been tested negative for. I took notice. A few weeks went by, I thought about all the things that had happened and realized that my bad luck started shortly after coming back from my island vacation.
After further research I realized the only thing that had changed in my life were these rocks. After reading that taking anything natural from the islands is considered bad luck, I promptly put the rocks into the mail and sent them back "home". My luck quickly changed to "good".
So was it Pele's Curse? I don't know, but guaranteed I have not and will not bring back any native elements from Hawaii. My souvenirs now are small trinkets, photos and life long memories.
See article on Black Sand Beaches.