@Celt_mane In the UK rock salt from mines like those in Winsford, Cheshire, is used to grit the roads when it is actually perfectly good for human consumption and basically the same as that posh pink himalayan rock salt.
@Celt_mane To form, salt must crystallise around something. Rock salt is usually microscopic pieces of rock. The sea is so full of microplasrics that it crystallises around them. Rock salt is your safer alternative.