MINERALS Chemical composition of the Crust Oxygen most abundant- 46.6% Followed by silicon and aluminum Iron, Calcium, Sodium, Potassium, Magnesium The most common minerals will be composed mostly of these elements Silica & silicates MINERAL vs. ROCK ROCK An aggregate of one or more MINERALS (usually- coal, organic) MINERAL Solid Crystalline- orderly arrangement of atoms Naturally occurring Inorganic Definite chemical composition e.g. SiO2 for quartz; KAlSi3O8 for feldspar Atom & Elements Atoms Neutral Nucleus Proton, Electron Ions Electrical neutron Charge Molecule- e.g. water molecule Chemical activity Stable atoms want positive & negative charges balanced electron shells full Ions- positive (Cations) and negative (Anions) Bonding Ionic Covalent Metallic Van der Waal’s Element Atomic number Number of PROTONS Isotope Differing number of NEUTRONS Atomic weight Mass of PROTONS and NEUTRONS Crystallinity 3 dimensional orderliness of atoms Silicon-oxygen tetrahedron Silicate structures Single- e.g. olivine Chain Single chain- pyroxene Double chain- amphibole Sheet- e.g. mica, clay Framework- e.g. quartz, feldspar MINERALS Crystalline solids Natural and Inorganic Substances Definite chemical composition Can be written as a chemical formula Solid solution (within a range) Important Minerals Quartz (most abundant) FELDSPAR Group Potassium Feldspar - Orthoclase Plagioclase Feldspar Sodium (Na) Albite Calcium (Ca) Anorthosite Important Minerals PYROXENE Group- Augite most common AMPHIBOLE Group- Hornblende most common MICA Group- Si + O in sheets Biotite Muscovite CALCITE- CaCO3 Properties of Minerals Color Not always reliable (Olivine, green; Flourite, yellow, purple, green…) Ferromagnesian minerals green or black Streak- powdered form Luster- reflectance of light Metallic Nonmetallic Vitreous Earthy or Glassy Properties of Minerals Hardness- resistance to scratching Moh’s Hardness Scale Fingernail = 2.5 Penny = 3.5 Knife/Glass = 5.5 Streak Plate= 6.5 Cleavage Properties of Minerals Quality (poor, good, perfect) Number of directions One- e.g. Mica Two at right angles- e.g. Feldspar, Pyroxene Two not at right angles- e.g. Amphibole Three at right angles (cubic)- e.g. Halite Three not at right angles (rhombohedral)- e.g. calcite Four (Flourite) or six (Sphalerite)- not common Properties of Minerals Fracture Absence of cleavage Irregular fracture Conchoidal fracture- Quartz Density Specific Gravity Some unusual properties Striations, refraction Magnetism, Taste, Odor, Double Chemical tests Reaction with HCl Calcite effervesces Mineral Groups Silicates Carbonates Oxides Sulfides Sulfates Native Elements Halides Silicates Quartz Feldspar Plagioclase Orthoclase Micas Muscovite Biotite Amphibole (Hornblende) Pyroxene (Augite) Olivine Carbonates Calcite (calcium carbonate) Dolomite (calcium-magnesium carbonate) Both are used as Portland Cement Oxides Hematite (iron oxide) Iron Magnetite Iron ore, pigment ore Corundum (aluminum oxide) Sapphire, Abrasive ruby (gemstone) Sulfides Galena (Lead sulfide) Lead Sphalerite Zinc sulfide) Zinc ore ore Pyrite (Iron sulfide) Sulfuric acid Chalcopyrite (Copper Iron sulfide) Copper ore Sulfates Gypsum Anhydrite Both use in plaster Native Elements Gold- trade, instruments Silver- photography, conductors Copper- electrical Platinum- catalysts Sulfur- chemicals, pharmaceuticals Diamond- carbon Gemstone, abrasive Graphite- carbon Lubricant, pencils ROCK CYCLE Equilibrium Interrelationships between igneous rocks sediment sedimentary rocks metamorphic rocks weathering and erosion Rocks Classification of Igneous, Sedimentary and Metamorphic Rocks IGNEOUS ROCKS EXTRUSIVE Volcanic- Fine-grained INTRUSIVE Plutonic- Coarse-grained MAGMA Molten Rock Usually with dissolved gasses Generated at depth Eruptions if magma (lava) reaches surface If doesn’t reach surface, Solidifies underground Intrudes country or host rock Intrusive contact Xenolith- ‘foreign body’ Igneous Rocks Names based on mineral composition reflects chemical composition of the magma and... Grain size Very coarse-grained Pegmatitic Coarse-grained: Phaneritic > 1 mm. Fine-grained: Aphanitic < 1 mm. Porphyritic- 2 crystal sizes Igneous RocksClassification Coarse-grainedPlutonic (Intrusive) Granite (Sialic) (SIlica and ALuminum rich) Diorite Gabbro (Mafic) (MAgnesium and iron (FE) rich) Dunite & Peridotite (Ultramafic) Fine-Grained Volcanic (Extrusive) Rhyolite (Sialic) Andesite Basalt (Mafic) Igneous Rock Identification Granite (& Rhyolite) High in Si + O Low in Fe + Mg Mostly feldspar & quartz Light-colored Basalt (& Gabbro) “Low” in Si + O High in Fe + Mg no quartz, abundant ferromagnesian minerals Dark colored Andesite (& Diorite- intermediate) COARSE-GRAINED PLUTONIC ROCK GRANITE WEATHERING, EROSION, TRANSPORTATION Weathering- Physical disintegration and chemical decomposition of rocks Erosion- Physical removal Transportation- Movement of eroded particles Chemical vs. Physical Weathering Physical Weathering ROCK CYCLE Relative Percentages of Sedimentary Rocks SEDIMENT Particle size Pebbles, cobbles, boulders Gravel- > 2mm Sand- 2mm - 0.063mm Silt - 0.063mm - 0.004mm Clay- < 0.004 Deposition Clay-sized particle vs. clay mineral TYPES OF SEDIMENTARY ROCKS Clastic or Detrital Chemical- inorganic precipitation or evaporation Biochemical- Organic remains shells, charcoal, plant fragments CLASTIC (Detrital) ROCKS Breccia and Conglomerate (> 2mm) Sedimentary Breccia- angular fragments Conglomerate- rounded fragments Sandstone (2mm - 0.063mm) Quartz sandstone Arkose (feldspar) Graywacke (appreciable amounts of silt/clay) Fine-grained Matrix Quartz Sandstone CHEMICAL SEDIMENTARY ROCKS Carbonate Rocks Limestone Inorganic made of calcite varieties • micrite, oolites, travertine Dolomite Recrystallization Chert- silica Evaporites Rock gypsum Rock salt MICRITE OOLITES Chert BIOCHEMICAL SEDIMENTARY ROCKS Coal Develops plant from peat fragments Lignite Bituminous Coal Carbonate Rocks Limestone organic made of calcite varieties • Coquina • Fossiliferous Limestone • Chalk Metamorphic Rocks Metamorphism Increase in Pressure; increase in Temperature Burial Contact Regional Metamorphic rock Pre-existing rock Parent rock Foliation Classification A- Slate C- Phyllite D- Schist E- Gneiss F- Migmatite Classification