Minerals: The Building Blocks! Lecture Notes PDF
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2006
Brian Cousens
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Summary
This document is a lecture on minerals focusing on their properties, definition, and relation to Earth's composition. The text details various mineral groups and properties like hardness, density, color, and crystal form. Information on silicate minerals and other important mineral groups is discussed. The document further touches on mineral occurrences in different Earth's layers, like the core, mantle, and crust. It references gemstones and their relation to the Earth's structure.
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California Coastlines, 2006 ERTH 1006 Minerals: The Building Blocks! Chapter 2 © Brian Cousens, 2024 Minerals Review Definition: naturally occurring, inorganic, homogeneous solid, fixed structure and composition Bonding: ionic, covalent, Van der Waals 9 mineral groups...
California Coastlines, 2006 ERTH 1006 Minerals: The Building Blocks! Chapter 2 © Brian Cousens, 2024 Minerals Review Definition: naturally occurring, inorganic, homogeneous solid, fixed structure and composition Bonding: ionic, covalent, Van der Waals 9 mineral groups Silicate minerals: silica tetrahedra – Isolated, single chain, double chain, sheet, framework 2 Minerals Review (con’t) Mineral properties: lustre, hardness, density, colour, streak, twinning, magnetism – habit, cleavage, fracture 3 1812 Carl Friedrich Mohs Hardness: Moh’s Scale Vickers Indentation Values: force to make small indentation 4 To Help You Remember: The talc Geologist gypsum Can calcite Find fluorite An apatite Ore orthoclase feldspar Quickly quartz Through topaz Correct corundum Data diamond 5 Density: “Specific Gravity” Weight of mineral relative to weight of equal volume of water Silicates: 2.5 - 3.3 Gold: 15! 6 Colour Sulfur Azurite Diagnostic for some minerals, not for others 7 Colour…. Quartz! 8 Streak: colour of powder Non-metallic minerals: white Metallic minerals: varies, but diagnostic Hematite - red Goethite - brown 9 Habit: crystal form Sulfur Galena Quartz GROWTH FACES - slow growth 10 Cleavage: breakage surfaces Planes of weakness in lattice Galena - cubic Amphibole - prismatic 11 Fracture - irregular breakage No planar weakness Quartz 12 Twinning Polysynthetic Growth or Twins Penetration Twins 13 Twins Staurolite Plagioclase (albite twin) 14 Magnetism Magnetite Fe3O4 (also Pyrrhotite FeS) 15 Other Properties: Taste (halite) Soapy feel (talc) Greasy feel (graphite, molybdenite, serpentine) Reaction with acid (calcite) Perthitic texture - exsolution of streaks of one mineral inside another (K-Na feldspar; orthopyroxene) 16 The Non-silicate Minerals Oxides Hematite Fe2O3 Magnetite Fe3O4 17 Carbonates Calcite CaCO3 Dolomite (Mg,Ca)CO3 Form in warm seawater 18 Sulfides Galena PbS Seafloor hydrothermal vents In volcanic systems, hot water leaches metals from rock, deposits metals above heat source Wikipedia 19 Seafloor Black Smokers 20 Sulfates Desert “playa” lakes Gypsum (CaSO4.2H2O) Death Valley Halite (NaCl) 21 Native Elements May 2004 Sulfur: Vulcano, Italy 22 Mineral Occurrences on Earth Earth is chemically zoned - core, mantle, crust Not surprising that the Earth is also mineralogically zoned? 23 The Core Outer Core: molten, no minerals Inner Core: solid, mineral structures unknown “Others”: Nickel, oxygen, sulfur, lead, uranium? 24 Mostly Mg-Fe The silicates Mantle Upper mantle: olivine, pyroxene Lower mantle: pyroxene, garnet, perovskite 25 Upper Mantle Rock “Peridotite” 26 Gemstones Peridot Garnet Birthstones: August, January 27 Diamonds - Carbon Graphite structure Diamond structure 28 Real Diamonds! 29 Diamond Stability Field geotherm: average Max thickness Ocean lithos. increase in temperature with depth. Diamonds stable >160 km depth beneath continents 30 How do diamonds get to the surface? Kimberlite pipe Kimberlite includes fragments of mantle rocks 31 How do you find kimberlites? Kimberlite soft, easily eroded (moved at surface) by glacier ice --> Commonly under lakes! 32 Glacial Dispersal Train 33 Other evidence for the composition of the mantle? Volcanic rocks: melts of the Earth’s mantle 34 The Crust Primarily silicate minerals Oceanic: olivine, pyroxene, Ca-feldspar (plagioclase) Continental: feldspar, amphibole, mica, quartz Continental Oceanic 35 The Feldspars Plagioclase (Ca) Potassium feldspar (K) Albite (Na) 36 Feldspar Associations Plagioclase (Ca) In Mg-Fe- rich, SiO2- poor rocks with olivine, pyroxene 37 Feldspar Associations Albite (Na) In rocks with intermediate SiO2 contents with pyroxene, amphibole or biotite 38 Feldspar Associations Potassium feldspar (K) In rocks with high SiO2 contents with mica, amphibole, quartz 39 How do Minerals Relate to Rocks? The Rock Cycle! Igneous Rocks Chapters 3,4 40
