Schist, Anglesey

The rocks of Anglesey include many that have been deeply buried, heated and altered, a process called metamorphism.

These rocks at Porth Dafarch originated as silts and muds on a sea floor some 600 million years ago, Later, they became deeply buried, squashed, and heated to temperatures approaching 500oC. During this process, the rocks have re-crystallised to form shiny mica-schist.

Phil Williams, www.geograph.org.uk/photo/158823