![Top curves](../../../../jsp/jahia/templates/GSL/gsl_templates/img/keystage3/main_top_grad.gif)
Schist, Anglesey
![schist hand specimen](../../../../webdav/site/GSL/shared/images/education_and_careers/RockCycle/RocksAroundBritain/Schist%20resized.jpg)
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.
Porth Darfach schist, Angelsey, North Wales
![Phil Williams, www.geograph.org.uk/photo/158823](../../../../webdav/site/GSL/shared/images/education_and_careers/RockCycle/RocksAroundBritain/PorthDarfachSchist%20xtrawide.jpg)
Phil Williams, www.geograph.org.uk/photo/158823
![Bottom curves](../../../../jsp/jahia/templates/GSL/gsl_templates/img/keystage3/bottom_curve.gif)