A useful introduction to the wide range of rocks in existence and a clear way of showing how rock is used for sculptures, buildings, jewellery, kitchen tools. Present the children with a range of rocks (chalk, marble, sandstone, slate, volcanic). Using a nail, ask the children to 'scratch- test' which type of rock is the hardest, ranking them in order. Can the children explain why chalk is used on classroom blackboards? Why is marble used for building? Equally, the compilation of clips could be used as a clip to reinforce knowledge of rocks and their uses.