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Earth’s Matter Minerals and Rocks Lesson 2.1 - Properties of Minerals For a substance to be a mineral, it must have all five of these characteristics 1. 2. 3. 4. 5. occurs naturally can form by inorganic processes (not part of living thing) has a crystal structure has a definite chemical composition and is a solid Minerals, Compounds, and Elements ● Almost all minerals are compounds ● Remember compounds are made of two or more elements bonded together ● Example: Quartz - one atom of silicon for every two atoms of oxygen ● Some elements occur in nature in a pure form: copper, silver and gold which are minerals as well. How are minerals identified? Each mineral has characteristic properties that can be used to identify it. ● color, streak, luster, hardness, density, crystal structure, cleavage, fracture, and special properties (bend light, glow, conduct electricity) How are minerals formed? In general, minerals can form in three ways. ● from organic processes. (clam shells) ● crystallize from materials that are dissolved in solutions. ● as magma and lava cools. Lesson 2.2 - Classifying Rocks How do geologists classify rocks? ● To study a rock sample, geologists observe the rock’s mineral composition, color, and texture. ● Rocks are made of mixtures of minerals and other materials. About 20 minerals make up most of the rocks of Earth’s crust. Mineral Composition and Color ● A rock’s color provides clues to the rock’s mineral composition. ● For example, granite is generally a light-colored rock that has high silicon content. Basalt is a dark-colored rock that has a lower silicon content. Texture ● Most rocks are made up of particles of minerals or other rocks, which geologists call grains. ● Grains give the rock its texture. Texture is the look and feel of a rock’s surface. Origin ● There are three groups of rocks that form in different ways. ○ Igneous rock forms from cooling magma or lava. ○ Most sedimentary rock forms when small particles of rocks or organic remains are pressed and cemented together. ○ Metamorphic rock forms when a rock is changed by heat, pressure, or chemical reactions. Lesson 2.3 - Igneous Rocks How Do Geologists Classify Igneous Rocks? ● All igneous rocks form from magma or lava ● However they can look vastly different from each other ● Classified by their origin, texture, and mineral composition. (see a pattern forming) ● It may form on or beneath Earth’s surface. Extrusive - from lava that erupted onto surface. (exited Earth) Intrusive - from magma hardening beneath surface. (inside Earth) How Are Igneous Rocks Used? ● People throughout history have used igneous rock for tools and building materials. ○ Granite - build statues, fortresses, bridges, and public buildings. ○ Basalt - cobblestones and as a material in landscaping and roads. ○ Pumice - good abrasive for cleaning and polishing. ○ Obsidian - make sharp tools for cutting and scraping. Lesson 2.4 - Sedimentary Rocks How Do Sedimentary Rocks Form? ● Sediment is small, solid pieces of material that come from rocks or living things. ● Sedimentary rocks form when sediment is deposited by water and wind. ● Most sedimentary rocks are formed through a sequence of processes: weathering, erosion, deposition, compaction, and cementation. The Three Major Types of Sedimentary Rocks ● clastic rock is a sedimentary rock formed when rock fragments are squeezed together. (ex. shale, sandstone, conglomerate) ● Organic rock forms where the remains of plants and animals are deposited in layers. (ex. coal and limestone) ● Chemical rock forms when minerals dissolved in a water solution crystallize. (ex. limestone and rock salt) How Are Sedimentary Rocks Used? ● People have used sedimentary rocks for many different purposes, including for tools and building materials. ○ Flint used to make spearheads and arrowheads. ○ Sandstone and limestone are used as building materials. Limestone is used to make cement and steel. What Are Metamorphic Rocks? ● Any rock that forms from another rock as a result of changes in heat or pressure (or both heat and pressure) ● It can change both its shape and its composition. How Metamorphic Rocks Form? ● Pockets of magma can rise through the crust. The high temperatures of these pockets can change rock ● Collisions between Earth’s plates can also push rock down toward the heat of the mantle. ● Plate collisions cause great pressure to be applied to rock while mountains are being formed. How Metamorphic Rocks are Classified? ● according to the arrangement of the grains ○ either in parallel layers or bands are said to be foliated. (most common) ○ Nonfoliated grains are randomly arranged (ex. marble) How Metamorphic Rocks Are Used? ● marble and slate are important materials for buildings and sculptures. ● Ground up marble is also a component of toothpaste, plastics, and paper ● Graphite, the “lead” in pencils, is a mineral commonly found in metamorphic rocks. What Is the Rock Cycle? ● a series of processes that occur on Earth’s surface and in the crust and mantle that slowly change rocks from one kind to another. ● Forces produce a slow cycle that builds, destroys, and changes the rocks in the crust. ● The changes of the rock cycle are closely related to plate tectonics. ○ help drive the rock cycle by helping to form magma, the source of igneous rocks. ○ The collision of continental plates can be strong enough to push up a mountain range resulting in sedimentary rock