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Chapter 2 Section 2

Chapter 2 Section 2. Minerals. What is a mineral?. What are the components of a mineral? Naturally occurring Solid substance Inorganic Orderly crystalline structure Definite chemical composition Ex: Quartz  SiO 2 (silicon & oxygen) ALL rocks are COMPOSED of minerals.

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Chapter 2 Section 2

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  1. Chapter 2 Section 2 Minerals

  2. What is a mineral? • What are the components of a mineral? • Naturally occurring • Solid substance • Inorganic • Orderly crystalline structure • Definite chemical composition • Ex: Quartz  SiO2 (silicon & oxygen) • ALLrocks are COMPOSED of minerals

  3. 1. Naturally Occurring • Minerals are formed by natural, geologic processes • Must naturally occur in nature, cannot be man-made • i.e. synthetic gems are not considered minerals.

  4. 2 & 3. Inorganic Solid Substance • Minerals are a solid…. not a liquid…not a gas. • within temperature ranges that are normal for Earth. • Inorganic crystalline solids found in nature • Table salt is a mineral  inorganic • Sugar is not mineral  organic • Exception: many marine animals secrete inorganic compounds • calcium carbonate minerals (coral reefs and in shells)

  5. 4. Crystalline Structure • Atoms are arranged in an orderly, repetitive structure (crystal lattice) • Ex: gemstone opal isn’t a mineral has the same elements as quartz (mineral) but NO orderly internal structure

  6. 5. Chemical Composition Pyrite “Fools Gold” FeS2 Au • A mineral has a chemical composition defined by a chemical formula • Compounds made of 2+ elements • Exceptions: gold & silver  1 element (native form)

  7. How Minerals Form • 4 major processes by which minerals form: • Crystallization from magma • Precipitation • Changes in pressure and temperature • Formation from hydrothermal solutions

  8. Crystallization from Magma • Magma = molten rock • Magma cools elements combine to form minerals • Ex: quartz & feldspar • First to crystallize ones rich in iron, calcium, and magnesium • Each mineral begins to crystallize at a different temperature

  9. Precipitation Mono Lake, CA limestone towers (calcite) formed underwater from calcium rich springs  exposed as sea level drops • All water in Earth’s lakes, rivers, oceans etc. contain dissolved substances • Water evaporates  dissolved substances react to form minerals • Change in water temperature  dissolved material precipitates out • Supersaturated • Ex: limestone caves, Great Salt Lake, Utah

  10. Pressure & Temperature • Existing minerals subjected to changes in pressure and temperature • Increase pressure • Minerals recrystallize while still solid • Atoms rearranged  forms compacted minerals • Change in temperature • Minerals may become unstable • Form new minerals  stable @ new temperature

  11. Hydrothermal Solutions • Very hot mixture of water & dissolved substances • Have temps. between 100°C and 300°C • Solutions come in contact w/ existing minerals chemical reactions occur  new minerals • Solutions cool  elements combine • Supersaturated • Ex: Bornite and chalcopyrite (sulfur minerals) formed from thermal solutions

  12. Mineral Groups Fluorite - a halide Okenite - a silicate Galena - a sulfide • Common minerals, together with the thousands of others that form on Earth, can be classified into groups based on their composition. • Silicates • Carbonates • Oxides • Sulfates and sulfides • Halides • Native elements

  13. Silicate Structure (Fe,Mg)2SiO4) iron-magnesium silicate • Most common group • Silicon and oxygen combine to form a silicon-oxygen tetrahedron • Tetrahedron consists of 1 silicon atom & 4 oxygen atoms  silicate • Silicon-oxygen tetrahedra can form chains, sheets, & 3-D networks • Super strong bonds • Ex: olivine-millions of single tetrahedra

  14. Silicate Formation • Most silicate minerals crystallize from magma as it cools • Can occur at or near surface of Earth (temp. and pressure low) • Weathering & mountain building  form silicates • Can occur at great depths (temp. and pressure high) • Location during formation & chemical composition of magma determines which silicate minerals will form • Olivine: 1200°C Quartz: 700°C

  15. Carbonates • 2nd most common mineral group • Contain the elements: • carbon • oxygen • one or more other metallic elements • Calcite (CaCO3): most common carbonate mineral • Limestone & marble  rocks that are composed of carbonate minerals

  16. Oxides • Contains: • Oxygen • One or more other elements (usually metals) • Ex: Rutile (TiO2) • Form as magma cools beneath Earth’s surface • Titanium oxide • Ex: Corundum (Al2o3) • Existing minerals  heat & pressure • Aluminum oxide

  17. Sulfates and Sulfides • Contain the element sulfur • Sulfates = • Ex: Anhydrite (CaSO4) • Ex: Gypsum (CaSO4  2H2O) • Forms when mineral-rich water evaporates • Sulfides = • Ex: Galena (PbS) • Ex: Pyrite (FeS2) • Forms from thermal solutions

  18. Halides • Contains: • Halogen ion • One or more other elements • Halogens from Group 7A in periodic table • Includes fluorine and chlorine • Halite (NaCl) i.e. table salt • Fluorite (CaF2) used in making steel • Forms when salt water evaporates

  19. Native Elements • Minerals in relatively pure form • Ex: Gold (Au), Silver (Ag), Copper (Cu), Sulfur (S), Carbon (C) • Native forms of carbon are diamond and graphite • Some form from hydrothermal solutions

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