This document discusses different types of rocks and their properties. It describes the three main types of rocks - sedimentary, metamorphic, and igneous rocks - and provides examples of each type. Key details about each rock type are given, such as sedimentary rocks often containing layers and fossils, metamorphic rocks usually being harder than sedimentary rocks and containing thin layers, and igneous rocks generally being the hardest and containing crystals. The document also discusses where rocks come from and the composition of the Earth's crust.