School of Environmental Sciences Photomicrographs - metamorphic rocks Click on an image to enlarge it and see a brief explanation The following images show metamorphic rocks. Some of these metamorphic rocks were produced when rocks were altered by an increase in temperature during contact metamorphism.  Others were formed when rocks were altered by temperature and pressure changes during regional metamorphism and these rocks show a foliation (an alignment of minerals). In these thin sections you should be able to recognise fine, medium and coarse crystal sizes.  Also try to identify the following: granoblastic texture, porphyroblastic texture, schisosity, gneissose banding and hornfelsic texture. .