B is for Black sand beaches

The North Islands beaches along most of the western coastline are remarkably different than those along the east.  Many of the rivers that drain the volcanic North Island flow out west, taking with them the dark coloured eroded sediments from past volcanic eruptions.  These sediments are very fine, almost dust like, and so get carried along the coastline by the currents and waves to form long glistening beaches.  On closer scrutiny, the ‘black’ colouring is from the moisture in the sand as the particles themselves are more of a grey colour.  The different sized particles are slightly different shades of grey and as a wave recedes, a rainbow of these shades is left behind in amazing patterns of art.