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Definitions

Definitions. Element A form of matter that cannot be broken down into simpler form by heating, cooling, or chemical reactions Mineral Naturally occurring solids consisting of one or more elements in specific proportions Rock

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Definitions

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  1. Definitions • Element • A form of matter that cannot be broken down into simpler form by heating, cooling, or chemical reactions • Mineral • Naturally occurring solids consisting of one or more elements in specific proportions • Rock • Naturally occurring aggregates or combinations of one or more minerals

  2. Periodic Table

  3. Most Abundant Elements in the Earth’s Continental Crust • Oxygen (O) – 46.6% • Silicon (Si) – 27.7% • Aluminum (Al) – 8.1% • Iron (Fe) – 5% • Calcium (Ca) – 3.6% • Sodium (Na) – 2.8% • Potassium (K) – 2.6% • Magnesium (Mg) – 2.09%

  4. Atomic Number / Atomic Weight • Atomic Number – number of protons in the nucleus (matched by equal number of electrons) • Atomic Weight – number of protons and neutrons in nucleus • Ions - Atoms with unequal number of protons and electrons are called ions • Cations have net positive charge (Ca+) • Anions have net negative charge (Cl-) • Isotopes - Atoms in which the number of neutrons varies from the number of protons (C12 and C14)

  5. Atomic Bonding • Covalent – atoms share electrons to fill outer shell • Ionic – Atoms gain or lose electrons to fill their outer shell (NaCl) • Metallic – shared by many atoms as in a cloud • Intermolecular – atoms bond to form molecules that have weak residual charges • Very strong • Strong • Moderate with freely roaming electrons • Weak – van der Waals

  6. Electron Valence and Electronegativity • Atomic nucleus • protons • neutrons • Electrically neutral atom has equal number of protons and electrons • Electrons fill valence shells from “inner to outer” • Cations- want to “give” electrons • K+ • Ca2+ • Anions- want to “take” electrons • Cl- • O2-

  7. Valence and Proportion • Superscript numbers indicate net electric charge AFTER electrons are either donated, received or shared • Subscript numbers indicate the number of atoms of that element needed to balance equation • Al23+O32- – corundum • Multiply valence state (superscript) by number of atoms (subscript) for each cation and anion • Multiplied values should cancel out for a balanced equation • Al (3x2)=6 vs O (-2x3)=-6 • Chromophores – impurities within the crystal or atomic lattice influence the color of a mineral • Cation substitution must have same valence state (e.g. Cr 3+ for Al 3+) • Substituting cations should be similar in size • Dictated by the ability of the atomic lattice to incorporate the new ion with minimal deformation or distortion

  8. Mineral Structure • Crystal - Unrestricted growth produces a regular geometric form • Atomic lattice – the orderly arrangement of ions or atoms expressed in three-dimensional form • Crystal structure – this form is directly related to a minerals atomic lattice

  9. Mineral Characteristics • Color – Most obvious but generally not a good indicator • Corundum (Al2O3) white to light gray • Chromium (Cr+3) = ruby • Titanium (Ti+3) = sapphire • Luster – good indication between metallic and others • Vitreous (glassy), adamantine (diamond), silky, pearly, earthy (dull) • Streak – color of mineral in its powdered form • Hematite – reddish-brown • Quartz - none

  10. Mineral Characteristics (cont’d) • Hardness – Mohs Hardness scale (p.89) • 1 – Talc • 10-diamond • Cleavage – tendency for minerals to break along planes of weak bondage (not the same as crystal faces) • Halite – cubes or 3-directions all perpendicular • Calcite – rhombs or 3-directions not perpendicular • Micas – perfect basal cleavage Fracture • Fracture – minerals that don’t have cleavage • Quartz – conchoidal

  11. Mineral Characteristics (cont’d) • Crystal Form – the 3-dimensional geometric shape minerals naturally grow into when the right conditions are met • Specific Gravity – the density of a mineral • Controlled by elemental make-up • Taste and smell – • halite (rock salt) have an easily identifiable taste (don’t try this on the lab samples) • Sulfur bearing minerals have a rotten-egg smell • Effervescence – fizzing or bubbling produced when HCl is applied (calcite)

  12. Cleavage PlanesFig. 3.23 • If you can see one plane on one side of a mineral specimen there MUST be a corresponding plane on the other side • Planes • 1,2 or 3 only • Perpendicular or non-perpendicular only • Look for shiny surfaces that spectrally reflect light • Not the same as crystal faces • Remember this is the real world

  13. Rock Forming Minerals • Over 3,000 mineral varieties on Earth • Only a few make up the most common rock-forming minerals • O & Si dominate Earth’s crust and mantle • Silicates are the most common rock-forming minerals

  14. Common Rock-forming Minerals(five major groups) • Silicates – (SiO4) most common w/silicon + oxygen • Olivine, Pyroxenes, Amphiboles, Micas, Quartz, Feldspars • Carbonates – (CO32-) carbonate ion complex and oxygen w/other atoms • Calcite • Oxides – (O2-) oxygen w/metallic ions • Hematite, Magnetite, Corundum • Sulfates – (SO42-) sulfur, oxygen and other metals • Gypsum • Sulfides – (S2-) sulfur and other metals (no O2) • Galena, Pyrite

  15. Silicates vs Non-silicates(Table 3.1 & 3.2) • Quartz (agate) • K-feldspars (orthoclase) • Ca-feldspars (plagioclase) • Micas (biotite) • Olivine (peridot) • Pyroxene • Amphibole • Clay minerals • Carbonates – calcite, dolomite • Oxides – hematite, magnetite, corundum • Sulfides – galena, pyrite • Sulfates – gypsum, anhydrite • Native – gold, silver, copper, diamond

  16. Minerals • Quartz – • One of the most common minerals, large group of varieties, found in igneous, meta and sed rocks, stable at surface, glass, paints, abrasives, computer chips, polarimeters, spectrographic lenses • Orthoclase – K-feldspar • Very common, found in felsic igneous rocks, some metamorphics, low-grade gems, w/qtz and kaolin makes porcelain, electrical insulators, dental products • Calcite – • Found in rock cavities, as cement for sed rocks, as carbonate deposits, used in polarizing prizms, construction (cement (lime) and ornamental stone (marble), fertilizers and chemical industry

  17. Minerals • Olivine – • Found in mafic and ultramafic igneous rocks, can be found as beach sand from volcanic islands, used in manufacturing of basic refractories, or as magnesium ore, gem quality peridot • Micas - • Found in igneous (pegmatities and granites) and metamorphic rocks (schists and amphibolites), used for elect and heat insulation, paper products, fireproof paint and dry lubricants • Hematite – • Found in extrusive igneous rocks and secondary mineral of sed deposits (oxidizing environment), most important iron ore, red ochre pigments and polishing powders

  18. Minerals • Galena – • Hydrothermal deposits w/qtz commonly, main ore of lead w/silver byproduct • Pyrite - • Found in igneous volcanic and hydrothermal deposits, as a diagenic deposit it replaces fossils or forms nodules, used to manufacture sulfuric acid and then treated to produce iron, gold, copper, nickel, etc • Halite – • From evaporation of saline waters, can form huge deposits at depth that migrate upward forming domes, used in fertilizers, food processing and chemical production

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