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Chapter 20

Chapter 20. Rocks and Minerals. The Geosphere is made up of Rocks and Minerals:. Minerals:. A naturally formed inorganic crystalline solid, composed of an ordered arrangement of atoms with a specific chemical composition . (pg.no.533).

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Chapter 20

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  1. Chapter 20 Rocks and Minerals

  2. The Geosphere is made up of Rocks and Minerals:

  3. Minerals: • A naturally formed inorganic crystalline solid, composed of an ordered arrangement of atoms with a specific chemical composition. (pg.no.533)

  4. In everyday usage, minerals are a part of our diet (“vitamins and minerals’’) and minerals provide the raw materials needed for industry (aluminum for cans, iron for steel, etc). • A mineral is a naturally formed, inorganic crystalline solid, composed of a determinable and ordered arrangement of atoms with a specific chemical composition. (pg.no.508)

  5. (pg.no.509)

  6. Grains of the mineral halite (table salt)

  7. Minerals are formed by crystallization the growth of a crystalline solid from a liquid or gas. • Crystallization starts when atoms begin to bond with each other in a particular geometric pattern. • As more and more atoms bond to the microscopic crystal, repeating the underlying pattern, the crystal grows. (pg.no.514)

  8. CRYSTALLIZATION IN MAGMA: • Magma is composed primarily of the elements found in the silicate group of minerals—namely, silicon and oxygen, plus aluminum, potassium, sodium, calcium, iron, and magnesium. When magma starts to cool, atoms in the hot liquid lose kinetic energy. Attractive forces then pull the atoms into orderly crystalline structures. Minerals crystallize from cooling magma in a systematic fashion, based on their respective melting points. (pg.no.515)

  9. High-silica-content minerals have low melting points. They are the first minerals to melt and the last minerals to crystallize. Low-silica-content minerals have high melting points. They are the last minerals to melt and the first minerals to crystallize. (pg.no.515)

  10. CRYSTALLIZATION IN WATER SOLUTIONS: • Minerals crystallize from water solutions in two main settings. The first is associated with the final stages of magma crystallization— magma generally contains from 1% to 6% water. When a body of magma is nearly solidified, this very hot water circulates through fractures in the new rock and often into the surrounding rock—hydrothermal activity. These water solutions usually contain many dissolved mineral constituents. The solutions become chemically saturated as the temperature decreases, causing various minerals to precipitate. These minerals are often deposited in cracks, and sometimes within the rock matrix itself.(pg.no.516)

  11. Rock Types: • Igneous rocks: Igneous rocks are formed by the cooling and crystallization of hot, molten rock. The word igneous means “formed by fire.” Plutonic igneous rocks are formed when molten rock below Earth’s surface—magma—cools. (pg.no.517)

  12. Sedimentary rocks:Sedimentary rocks are formed at or near Earth’s surface from the cementation or compaction of sediment—rock, mineral, shell, or solid organic fragments carried by water, wind, or ice and deposited in low-lying areas. Sedimentary rocks also form when minerals precipitate out of water solutions at or near Earth’s surface. Sandstone, shale, and limestone are common sedimentary rocks.(pg.no.518)

  13. Metamorphic rocks: Metamorphic rocks are formed from older, preexisting rocks (igneous, sedimentary, or metamorphic) that were transformed in Earth’s interior by high temperature, high pressure, or both—without melting. The word metamorphic means “changed in form.” For example, marble is metamorphosed limestone, and slate is metamorphosed shale.(pg.no.518)

  14. End of The Chapter

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