Geology of Durness

Above the Moine Thrust at Sango Bay are well developed metamorphic rocks knows as 'mylonites' that were once part of the Lewisian Gneiss (now deformed). Mylonite is a ductilely deformed rock formed by shear stress. It is generally attributed to be a metamorphic rock. In the photo above, small and abundant microfaults can also be seen slicing up the different coloured layers

These mylonites have formed by recrystallisation of the Lewisian basement as a response to shear pressure and deformation along the Moine Thrust. The recrystallisation of the rock has also allowed it to become smaller in grain size. Mylonites generally develop in ductile shear zones where high rates of strain are focused into thin layers. They are the deep counterparts to cataclastic brittle faults that create breccias (cataclasites also found present below cliff face).