Classification of Rocks Classifying Rocks Igneous rocks are classified according to their origin, texture, and mineral composition. Origin Did it harden inside the earth or on the earth’s surface? Texture Is it fine or coarse grained? Mineral Composition Is it dark colored, which is low in silica or light colored, which is high in silica? from lava from magma Which of the following igneous rocks are extrusive? How do you know? 1 2 3 4 5 6 7 8 9 This sediment can include minerals, small pieces of plants or other organic matter. It is compressed over a long period of time before creating a rock. Sedimentary rocks are formed by sediment that is deposited over time, usually as layers at the bottom of lakes and oceans. Fossils can be found in sedimentary rock. Sedimentary Rock clastic chemical organic from from from rock particles once living organisms… plants & animals dissolved minerals in solutions or water that crystallizes Categorized by: particle size plant • shale • coal • rock salt • sandstone • limestone • gypsum • conglomerate animal Metamorphic Rocks Metamorphic rocks are formed when other rocks are exposed to years of heat and pressure. Foliated: grains are arranged in layers, or “bands.” slate Non-foliated: no layered “bands.” marble schist phylite gneiss quartzite Metamorphic Rocks Follow the arrows! granite marble limestone Metamorphic Rocks Shale Slate Sandstone Quartzite That was fun!