Polarised light micrograph of a local expression of mylonite, known as Pfitscher Schiefer, from Pfitschtal, South Tyrol, Italy. Mylonites are ductilely deformed rocks formed by the accumulation of large shear strain in ductile fault zones. They have a distinctive layered texture and a linear structure that shows the direction of the tectonic movement. Mylonites can have many different mineralogical compositions, as classification as mylonite is based on the textural appearance of the rock. Pfitscher Schiefer is a greenschist with serpentine, magnetite, tourmaline and breunnerite. Magnification: x60 when printed at 15 centimetres wide.