[Observations/teaching points] Look closer: What are these rocks made of? [Teacher information] Rock Names: An igneous rock, similar to granite, called granophyre [“grano-fire”] A sedimentary rock called quartzite, a hard sandstone. An igneous rock called dolerite [basalt has even finer crystal size]. A sedimentary rock called conglomerate. Looks like concrete! [Interpretation/comments] 
Use a magnifier. Pinkish rock contains white and pink minerals [quartz and feldspar] as interlocking crystals rather than grains. Pale grey rock has similar sized fragments of quartz sand grains, cemented together by quartz. Black rock contains mostly small black crystals with a few grey ones. Mixed coloured rock contains bits of various sizes including pebbles of different rocks and quartz sand grains cemented together. Some of the pebbles are recognisable rock types e.g. the pinkish rock.