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What is a mineral? Objectives • Define a mineral. • Describe how minerals form. • Identify the most common elements in Earth’s crust. What is a mineral? What is a mineral? • Earth’s crust is composed of about 3000 minerals. • Minerals form rocks and shape Earth’s surface. • Some have played a role in shaping civilization. What is a mineral? Mineral Characteristics • A mineral is a naturally occurring, inorganic solid with a specific chemical composition and a definite crystalline structure. What is a mineral? Mineral Characteristics Naturally Occurring and Inorganic – they are formed by natural processes. – they aren’t alive and never were. What is a mineral? Mineral Characteristics Solids with Specific Compositions – All minerals are solids . – Unique chemical composition. – Vast majority are made from compounds. Fe2O3 SiO4 NaCl What is a mineral? Mineral Characteristics Definite Crystalline Structure – A crystal is a solid in which the atoms are arranged in repeating patterns. Tetragonal Cubic Triclinic Orthorhombic Hexagonal Monoclinic What is a mineral? Mineral Characteristics Definite Crystalline Structure Cubic What is a mineral? Mineral Characteristics Definite Crystalline Structure What is a mineral? Minerals From Magma • Magma is molten material found beneath Earth’s surface. • Rapidly cooling magma = Small crystals • Slowly cooling magma = Large crystals What is a mineral? Minerals From Magma What is a mineral? Minerals from Solution • Saturated: a solution holds as much solute as possible (filled-up) – Precipitation: solids form out of saturated solutions. – Evaporation: elements left behind arrange into crystals (evaporites). What is a mineral? Mineral Groups • About 30 minerals are common in Earth’s crust. • These are mostly the rock-forming minerals. • Vast majority of minerals are made up of only eight common elements. What is a mineral? Mineral Groups What is a mineral? Mineral Groups Silicates – Silicates are minerals that contain silicon and oxygen, and usually one or more other elements. – 96 percent of the minerals in Earth’s crust. – Most common minerals: feldspar and quartz What is a mineral? Mineral Groups Carbonates – One or more metallic elements + the carbonate ion, CO3. – limestone, coquina, and marble. (calcium carbonate) What is a mineral? Mineral Groups Oxides – Oxides are compounds of oxygen and a metal. – Hematite (Fe2O3) and magnetite (Fe3O4) are common iron oxides and good sources of iron. What is a mineral? Mineral Groups What is a mineral? Section Assessment 1. Match the following terms with their definitions. ___ B mineral ___ C crystal ___ D magma ___ A silicate A. minerals that contain silicon and oxygen, and usually one or more other elements B. a naturally occurring, inorganic solid with a specific chemical composition and definite crystalline structure C. a solid in which the atoms are arranged in repeating patterns D. molten material found beneath Earth’s surface What is a mineral? Section Assessment 2. What are the two ways that minerals can form from a supersaturated solution? Mineral crystals can precipitate, or drop out of solution if the solution becomes supersaturated. Minerals can also form when liquid evaporates from a supersaturated solution leaving behind the elements which may begin to arrange into crystals. What is a mineral? Section Assessment 3. Identify whether the following statements are true or false. _______ true There are about 30 common minerals in Earth’s crust. _______ false Slowly cooling magma produces small crystals. _______ false Coal is a mineral. _______ true Silicates are the most common minerals on Earth. _______ true Well-defined crystal shapes are rare. End of Custom Shows This slide is intentionally blank.