Themes of the Day:

• Minerals Defined
• Basic Chemistry Review
• Chemical Bonding and Crystalline Structures
• Physical Properties
• Important Minerals

Minerals Defined

• Definition
  • Occurs Naturally
  • Inorganic
  • Solid
  • Characteristic Chemical Formula
  • Crystalline Structure
• Mineral - Yes or No? Examples: coal (Kentucky's state "mineral"), cubic zirconia, pearl, mercury, glacier ice, volcanic glass, etc.

Musical Interlude: The Elements by Tom Lehrer (music by Sir Arthur Sullivan). Sing along!
Now also available in a Flash animation!!!

Basic Chemistry Review

• Minerals are built from atoms that are chemically bonded together in crystalline lattices.
• The Atom: Nucleus (Protons, Neutrons), Electrons
• Isotopes (variable numbers of neutrons) used for isotopic age dating
• Ions - charged atoms with # of electrons not equal to # of protons - important for bonding
  • Anions - negative charge - # of Electrons > # of Protons - ex. Chlorine (Cl^-), Oxygen (O^2-)
  • Cations - positive charge - # of Electrons < # of Protons - ex. Sodium (Na⁺), Magnesium (Mg²⁺)
• Periodic Table - helps predict ionic charges
• Ions with similar charges and sizes may substitute for each other in some minerals
• Abundance of elements in the Earth's crust:

  Element	Chemical Symbol and Common Ion(s)	Percent (by weight)
  Oxygen	O2-	46
  Silicon	Si4+	28
  Aluminum	Al3+	8
  Iron	Fe2+ or Fe3+	6
  Magnesium	Mg2+	4
  Calcium	Ca2+	2.4
  Potassium	K1+	2.3
  Sodium	Na1+	2.1
  All others		<1

Chemical Bonding and Crystalline Structures

• Bonding is what happens when ions share electrons.
• Four basic types
  • Ionic bonds - electron(s) completely transferred - e.g., Halite (NaCl) - tend to be brittle bonds
  • Covalent bonds - electron(s) more evenly shared - e.g., Diamond (C) - strong bonds (diamond is strongest)
  • Metallic bonds - transition metal nuclei swimming in a sea of shared electrons - e.g., Gold (Au) - malleable
  • Intramolecular bonds - including hydrogen bonds and Van der Waals bonds - generally weak (often feels greasy) - e.g., graphite (C) or talc (Mg₃AlSi₃O₁₀(OH)₂)
• Silicate minerals, containing covalently bonded SiO₄ tetrahedra are most common in Earth's crust and mantle - subclassification system for silicates based on linkages of the SiO₄ tetrahedra
• Unit Cell - smallest building block that has all of a mineral's structural and chemical characteristics
• Crystal Systems - mineral groupings based on internal symmetry - sometimes reflected in ideal crystal shapes - e.g. quartz and ice belong to the Hexagonal crystal system, halite is cubic
• Bond types and crystaline structure are directly related to physical properties (see below) - e.g. Diamond & Graphite

Physical Properties

• Habit - naturally occuring shape of crystals
• Cleavage - planar surfaces along which a mineral tends to break preferentially (related to weak bonding planes within a mineral's crystal structure - e.g., micas, halite, pyroxenes &amphiboles
• Fracture - non-planar breakage behavior of a mineral - e.g., choncoidal fracture in glass or quartz
• Hardness - resistance to scratching (also reflects bond strength) - Mohs' Hardenss scale
• Specific Gravity - very similar to density
• Color - often distinctive, sometimes variable or unreliable
• Streak - color of powdered mineral - not always the same as color of unpowdered mineral
• Luster - degree of reflectivity - e.g., galena - metallic, quartz - glassy, chalk - dull or earthy
• Special Properties:
  • Magnetism - a magnet is attracted to the mineral magnetite (Fe₃O₄)
  • Aroma (odor) - some sulfur-bearing minerals stink like rotten eggs when scratched
  • Taste - halite (NaCl - rock salt) tastes salty (duh!)
  • Acid Reaction - calcite (CaCO₃ - the mineral that makes up limestone) effervesces when you drop acid on it

Important Minerals

• Common Rock-Forming Minerals - mostly silicates
  Igneous Rocks
  • Ferromagnesian Minerals - Olivine, Pyroxene, Amphibole, Biotite - Dark in color, common in mafic rocks
  • Feldspars - Plagioclase, Orthoclase (K-feldspar)
  • Quartz
  Sedimentary Rocks
  • Quartz & Feldspar
  • Clay Minerals
  • Carbonate Minerals - Calcite & Dolomite
  • Evaporite Minerals - Halite, Gypsum
  Metamorphic Rocks
  • Most of the above, plus:
  • Micas, Garnet, Aluminosilicate Polymorphs (Andalusite, Kyanite, Sillimanite), and many more...
• Ore and Industrial Minerals
  • Native Elements - Gold, Silver, Copper, Sulfur, Graphite, Diamond
  • Oxides - Iron Oxides (Hematite, Magnetite, Limonite), Chromite, others
  • Hydroxides - Bauxite (aluminum ore)
  • Sulfides - many metal ores (Cu, Pb, Zn, Mo, Hg, Ni, etc.) - potential environmental hazards in mining and refining
  • Sulfates - Gypsum (main constituent of Sheetrock), Barite (drilling muds)
  • Halides - Halite (rock salt - many uses), Sylvite (K for fertilizer), Fluorite (Fluorine)
  • Carbonates - Calcite (many uses)
  • Phosphates - Apatite (P for fertilizer)