Minerals of Earth

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Chapter 5

• Minerals of Earths Crust

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Sect. 1 What is a Mineral?

• Objectives
• Define mineral
• Compare the two main groups of minerals
• Identify the six types of silicate crystalline
  structures
• Describe three common nonsillicate crystalline
  structures

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Mineral

• Gold, grain of sand, calcite
• Natural, usually inorganic solid that has a
  characteristic chemical composition, an orderly
  internal structure, a characteristic set of
  physical properties

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Characteristics of Minerals

• 1. Is it inorganic?
• 2. Does it occur naturally?
• 3. Is it a crystalline solid?
• 4. Does it have a consistent chemical
  composition?
• If YES to all four questions, then its a MINERAL

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Kinds of Minerals

• 20 common minerals that make up Earths crust
• Two main groups
• Silicates
• nonsilicates

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Silicate Minerals

• Contains combination of Si, O, make up 96 of
  earths crust
• Quartz- only Si O
• Feldspars-orthoclase- Si, O and K, plagioclase-
  Si, O, and Na, or Ca, or both
• Ferromagnesian minerals- Si, O, Fe, Mg
• Examples- olivines, pyroxenes, amphiboles,
  biotite

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Silicate Minerals
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Nonsilicate Minerals

• Approx 4 of Earths crust
• Do NOT contain Si O
• Six major classes of nonsilicate minerals

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Carbonates

• Compounds that contain a carbonate group (CO3)
• Dolomite CaMg(CO3)2, Calcite CaCO3

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Carbonate
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Halides

• Compounds that consist of Cl, F combined w/ Na,
  K, or Ca
• Halite NaCl, Fluorite CaF2

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Halide
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Native elements

• Elements uncombined with other elements
• Silver Ag, Copper Cu, Gold Au

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Native element
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Oxides

• Compounds that contain O and an element other
  than Si
• Corundum Al2O3, Hematite Fe2O3

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Oxides
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Sulfates

• Compounds that contain a sulfate group (SO4)
• Gypsum CaSO4 ? 2H2O, Anhydrite, CaSO4

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Sulfates
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Sulfides

• Compounds that consist of one or more elements
  combined with sulfur
• Galena PbS, Pyrite FeS2

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Sulfides
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Crystalline Structure

• Crystal- a solid whose atoms, ions, or molecules
  are arranged in a regular, repeating pattern
• Minerals that form in a large space may grow into
  one or more large crystals
• The mineral will take the shape of 1 of 6 major
  crystal systems

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Crystalline Structure of Silicate minerals

• Many kinds of silicate minerals- 1 building block
  4 oxygens, 1 silicon

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Arrangements of silicate minerals

• Isolated tetrahedra- Mg, Fe,olivine
• Ring silicates
• Single chain silicates-pyroxenes
• Double chain silicates-amphiboles
• Sheet silicates-muscovites, biotite
• Framework silicates-quartz

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Crystalline structure of nonsilicate minerals

• Have an extreme diverse chemical composition
• Vast variety of crystalline structures

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Sect.2 Identifying Minerals

• Study properties of minerals
• Use properties to identify classify them

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Color

• Most noticiable characteristic of minerals
• It is one of the least reliable characteristics
  b/c many minerals have several varieties with
  different colors

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Varieties of quarts
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