|
Clerical:
Leftover Exam #2 returned - Exam #2 Grade Distribution.
Quizzes 9-12 are posted.
Themes of the Day:
- Chemical Bonding & Crystalline Structures (continued)
- Physical Properties
- Mineral Classification
- Silicate Subclasses
- Important Minerals
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
- 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
Mineral Classification
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)
- Ore Deposit Origins
- Plate Tectonic Settings of Some Common Types of Ore Deposits
- Mining Methods
- Worldwide Distribution of Ores
|
