Classifying Rocks • Rock- a mixture of minerals and other materials • Rocks are classified or grouped by: • 1) Mineral Composition and Color • Mineral Composition or the minerals that make the rock. • (Must use physical properties like color, streak, and luster to identify minerals) • Color: the colors of the minerals make the rock either light or dark • 2) Texture- • Grains – particles of minerals 3) Origin- how rocks are formed 3 Types of Rocks 1. Igneous 2. Sedimentary 3. Metamorphic
Igneous Rock Notes Igneous Rocks are formed from melting and cooling magma and lava. Intrusive Igneous Rocks are formed from cooled magma (inside the Earth) Extrusive Igneous Rocks are formed from cooled lava (exterior or out the Earth) Large mineral grains = Cooled slowly Small fine mineral grains = Cooled quickly Magma rises up because molten material is less dense than the solid rock around it. Igneous rocks are sometimes called parent rocks because they come from inside the Earth. All rocks come from igneous rocks originally.All rocks came from Volcanoes originally!
Intrusive Rocks • Are formed from magma • They have large mineral grains • slow cooling
Extrusive Igneous Rocks • Are formed from lava • Small mineral grains • Cool quickly
These igneous rocks have the same mineral composition Rhyolite Granite Intrusive Cools slowly Large mineral grains • Extrusive • Cools quickly • Small mineral grains
Andesite Extrusive or Intrusive? Did this rock cool slowly or rapidly?
Basalt Extrusive or Intrusive? Did this rock cool slowly or rapidly?
Pegmatite Extrusive or Intrusive? Did this rock cool slowly or rapidly?
Welded Tuff Extrusive or Intrusive? Did this rock cool slowly or rapidly?
Scoria Extrusive or Intrusive? Did this rock cool slowly or rapidly?
Sedimentary rocks are formed by compaction and cementation of sediment • Sediment is the particles that make up sedimentary rock. • Sediment may include pieces ofrock, shell, or bone. • Most sediment comes from erosion. • In erosion, moving water, wind, or ice loosens and carries away pieces of rock. • When the moving water, wind, or ice slows down, it drops the sediment. • This is called deposition. • Layers of sediment build up over millions of years. • Newest layers press down on older layers. • This squeezes the sediment together. • The squeezing is called compaction • . • Water seeps between sediment particles. • Dissolved minerals in the water form crystals. • The crystals “glue” the sediment particles together. • This is called cementation
Sedimentary rocks have layers or they have pieces of rock and other materials embedded in the rock. Sedimentary rocks are the only rocks that have fossils in them. *Igneous and Metamorphic rocks can be changed into sedimentary rocks if they are broken down into sediment.
Sedimentary rocks are classified by the kind of sediments they are made of. • There are three major groups of sedimentary rocks: • Clastic rock is made of rock particles. The particles can be tiny or huge. Sandstone is clastic rock. Sandstone is made of particles of sand. • Organic rock is made of the remains of plants and animals. • “Organic” means alive or once living. Limestone is organic rock. • Limestone is made of bones and shells • Chemical rock is made of dissolved minerals that came out of solution and formed crystals. Rock salt is chemical rock. Rock salt forms when a solution evaporates and leaves behind crystals of halite
Conglomerate Clastic, organic or chemical?
Shale Clastic, organic or chemical?
Sandstone Clastic, organic or chemical?
Bresccia Clastic, organic or chemical?
Rock into a Metamorphic Rock. Igneous and Sedimentary rocks can change into metamorphic rocks through heat and pressure The deeper a rock is buried the more heat and pressure is added to the rock. Metamorphism occurs between 200-800 degrees Celsius. (Hot but not quite melted) Rocks melt above 800 degrees Celsius. (become igneous) When rocks change into a metamorphic rock its appearance, texture, crystal structure, and mineral content can also change. There are 2 types of Metamorphic Rocks Foliated- mineral grains lined up in bands/lines Non foliated- mineral grains are not lined up in lines/bands
marble limestone Heat = pressure
Slate Shale Heat = pressure
Quartzite Sandstone Heat = pressure
Gneiss Granite Heat = pressure
Gneiss Foliated or non foliated?
Hornfels Foliated or non foliated?
Schist (Muscovite Schist) Foliated or non foliated?
Phyllite Foliated or non foliated?
Marble Foliated or non foliated?
Match the Rock Type with it’s Characteristic