Introduction to Minerals

Pamela J. W. Gore
Georgia Perimeter College

Objectives

1. Distinguish between rocks and minerals.
2. Distinguish the three basic subatomic particles, understand atomic mass, atomic number, radioactivity, isotopes, and ions.
3. Describe the various type of bonding in chemical compounds (ionic, covalent, metallic).
4. Describe the process of crystallization in minerals.
5. Distinguish the physical properties that are useful in identifying minerals.
6. List the eight most common elements of the earth's crust.
7. Briefly describe the silicon-oxygen tetrahedron.
8. List and distinguish among the common silicate minerals.
9. List the economic uses of some common minerals.
10. Describe the chemical classification of minerals.

Outline

Definitions

Physical Properties of Minerals

Chemical Properties of Minerals

  1. Basics of Chemistry
  2. Bonding
  3. Chemical Classification of Minerals
  4. Silicate Structures

Definitions

Mineral
  1. Naturally occurring
  2. Inorganic
  3. Solid
  4. Definite chemical composition
  5. Orderly internal crystal structure

Examples?

Link to crystal structure movies

Rock

An aggregate of one or more minerals

Examples?

Polymorphs

 Two minerals with the same chemical composition, but a different crystal structure.

Examples?

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Physical Properties of Minerals

  1. Color

    2. not always diagnostic (feldspar, quartz, fluorite)

    Feldspar can be green, pink white, gray, etc.

  2. Luster

    3. metallic
    non-metallic
          glassy or vitreous, dull, pearly,
          resinous, waxy, adamantine, silky

  3. Streak

    4. unglazed porcelain plate
    note color, odor if any

    Both of these samples are hematite; both have a reddish-brown streak

  4. Hardness

    5. scale of 1 to 10 (Mohs Scale)

    1. Talc
    2. Gypsum
      ________ fingernail
    3. Calcite
      ________ penny (copper)
    4. Fluorite
      _________ nail
    5. Apatite
      _________ glass
    6. Orthoclase feldspar (K feldspar)
    7. Quartz
    8. Topaz
    9. Corundum
    10. Diamond

  5. Cleavage

    6. Breakage along planes
    Related to crystal structure

    1 direction

    (muscovite, biotite)

    Muscovite (left) Biotite (right)

    2 directions at 90°

    (feldspar, pyroxene)

    Pyroxene

    2 directions not at 90°

    (amphibole at 60° and 120°)

    3 directions at 90° (cubic)

    (halite, galena)

    Halite

    3 directions not at 90° (rhombohedral)

    (calcite, dolomite)

    Cleavage fragments of calcite

    4 directions (octahedral)

    (fluorite)

    Cleavage fragments of fluorite

    6 directions

    (sphalerite)

  6. Fracture

    7. irregular breakage (no cleavage)
    breakage not along smooth planes

    Conchoidal fracture

    smooth curved fracture surfaces
    occurs in quartz, chert, obsidian, glass


    Rose quartz lacks cleavage; it has conchoidal fracture


    Conchoidal fracture in the igneous rock, obsidian

  7. Crystal form

    8. Some minerals that may or may not have cleavage GROW (not break) into crystals with flat sides.

    Examples -
    quartz
    pyrite

    Quartz crystals

  8. Density

    9. Density = mass divided by volume

  9. Specific gravity

    10. (similar to density)

    Weight of a mineral divided by weight of an equal volume of water.

  10. Magnetism

    11. Can be picked up by a magnet or may be a natural magnet

  11. Reaction to hydrochloric acid (HCl)

    12. Calcite effervesces in acid

    CaCO3 + 2HCl = CO2 + H2O + CaCl2

    Dolomite CaMg(CO3)2
    Must be scratched and powdered to fizz

  12. Taste

    13. halite, sylvite

  13. Fluorescence

    14. Some minerals glow in the dark under a black light (U.V. light)

    Due to excitation of electrons


    Fluorescent minerals under ultraviolet (black) light.

  14. Double refraction

    15. Light passing through the mineral is split into two rays. Causes an optical "doubling" effect.

    Calcite

    Calcite has the optical property of double refraction. In the photos above, the same sample of calcite is used. It is rotated over a thin dark line. Examine how the appearance of he line changes inthe different orientations of calcite.

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    Chemical properties of minerals

    A. Basics of Chemistry

    Atom - The smallest particle of matter with constant properties

    protons (+)
    electrons (-)
    neutrons (o)

    Nucleus of atom contains neutrons and protons.

    Electrons orbit the nucleus.

    In a stable atom, the number of electrons = the number of protons.

    Atomic number - The number of protons in the nucleus determines the atomic number

    change the number of protons and you change the element

    Ion - A charged particle, due to a change in the number of electrons

    Cation - positively charged ion (has lost one or more electrons)
    Anion - negatively charged ion (has gained one or more electrons)

    Isotope - A form of an element with a different number of neutrons

    Atomic weight (or mass number) = number of protons + number of neutrons

    Mass number   146C 
Atomic number 
				
			number of protons = _________
                        number of neutrons = _________



          126C 

                     number of protons = _________
                     number of neutrons = _________

    B. Bonding
    1. Ionic bonding involves electron transfer
      ex. Na+1Cl-1
      An electron has been transferred from the Na to the Cl

    2. Covalent bonding involves electron sharing

    3. Metallic bonding - electrons are free to move
      ex. metals (conduction of electricity)


    Click here to see a pie diagram of elemental abundances Return to Outline

    C. Chemical classification of minerals
    1. Native elements (metal)
      native gold (Au), native copper (Cu), native sulfur (S), native silver (Ag), graphite (C), diamond (C)
    2. Sulfides (metal + S)
      pyrite (FeS2), galena (PbS), sphalerite (ZnS)
    3. Sulfates (metal + SO4)
      gypsum (CaSO4 · 2H2O), anhydrite (CaSO4), barite (BaSO4)
    4. Oxides (metal + O)
      water ice (H2O), hematite (Fe2O3), magnetite (Fe3O4), corundum (Al2O3)
    5. Halides (metal + Cl or F halogens)
      halite (NaCl), fluorite (CaF2)
    6. Hydroxides (metal + OH)
      limonite (iron hydroxide), bauxite (aluminum hydroxide)
    7. Carbonates (metal + CO3)
      calcite (CaCO3), dolomite (CaMg(CO3)2)
    8. Phosphates (metal + PO4)
      apatite
    9. Other - borates, urananates
    10. Silicates (metal + Si and O)
      quartz (SiO2),
      potassium feldspar (KAlSi3O8),
      Ca Plagioclase feldspar (CaAl2Si2O8),
      Na Plagioclase feldspar (NaAlSi3O8)
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    Silicate Structures

     Based on silicate tetrahedron
    4 oxygen atoms and 1 silicon atom

    Click here for more information on the silica tetrahedron

    1. Single tetrahedra
      olivine

    2. Single chains
      pyroxene

    3. Double chains
      amphibole

    4. Sheets
      muscovite
      biotite

    5. Frameworks
      quartz
      feldspar
      potassium feldspars (orthoclase and microcline)
      plagioclase feldspars

    Return to Outline

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    Copyright 2000 Pamela Gore

    This page created by Pamela J. W. Gore
    Georgia Perimeter College, Clarkston, GA

    Created August 2, 1995
    Modified January 22, 1997
    Modified September 21, 1998
    Modified July 17, 1999
    Last modified August 20, 2000