It might not be as odd as some, but the cliffs along Penarth beach are home to literally thousands of tons of pink calcite. It's quite surreal to walk along Penarth beach just after some really wet weather (when there are quite often areas of landslide from the cliffs), and to see hundreds of chunks of the stuff just lying along the beach, as if the world's biggest blancmange just exploded!
Penarth beach is also AMAZING for fossil hunting too, if that's your thing. It's also a great time to go down there at the moment too, as tons of fresh rock has been washed off the cliffs after the recent weather.