Minerals and Rocks Chapter 20 Midterm 2 Distribution of Grades 30 25 20 15 10 A 26 B 18 C 24 D 22 F 21 5 0 90 89 80 79 70 score range 69 60 less Grades to date 2 19 09 40 Distribution of Grades to Date 35 30 25 20 15 10 5 A 29 B 24 C 22 D 16 F 14 0 90 89 80 79 70 score range 69 60 less Emily and Megan Earth System Science Interconnected Rocks and minerals Interior processes Erosion and deposition Water and air Elements of Earth Made of atoms Earth is mostly iron by weight Crust Elements Made of atoms Earth is mostly iron by weight Surface is mostly oxygen by weight Minerals Naturally occurring Not composed of organic molecules Crystalline solid Specific chemical composition Crystals Halite crystals NaCl Crystals Amethyst quartz Pyrite Shape reflects internal arrangement of atoms Rhodochrosite Asbestos Mineral Classification Crust is mostly oxygen and silicon Silicon always bonded to oxygen SILICATES 92 of minerals of crust Silicate Minerals Silica bonded to metals Aluminum sodium potassium calcium Feldspar Most abundant mineral felsic minerals Pale less dense than ferromags Examples of felsic minerals Feldspar Quartz Muscovite mica Silicate Minerals Silica bonded to metals Iron magnesium Ferromagnesian silicates ferromags Dense dark Examples of ferromags Amphibole Pyroxene Biotite mica Olivine Silicate Structure Hardness Resistance to scratching Compare to glass steel penny fingernail Breaking minerals Strength of bonds within crystals Cleavage Some planes with weak bonding Break along these Breaking minerals Strength of bonds within crystals Fracture No planar arrangement of weak bonds Conchoidal or irregular Non silicates Carbonates Calcite CaCO3 Oxides Fe2O3 Fe3O4 tin chromium uranium Sulfides Zinc lead mercury Pyrite FeS2 Native elements Au Cu Minerals crystallize From liquid usually or gas occasionally Magma molten rock Watery solutions Crystallization of Magma Cools atoms attracted to one another Arrange in orderly crystalline structures When very hot low silica forms Cooler greater amounts of silica in them Composition of magma changes as crystallization proceeds Crystallize from watery solutions Change solubility by changing physical or chemical conditions in magmatic water left pH other ion content Temperature pressure Chemical sedimentary rock Carbonates made by organisms mostly Increase concentration by evaporation evaporites Rock Types Igneous Sedimentary Metamorphic Sedimentary rocks Cover 2 3 of Earth s surface Record conditions at time of deposition Include remains of organisms preserved as fossils Sedimentary rocks Sediment is derived from weathering Carried by fluid Formed at Earth s surface Important to reconstruct much of Earth s history Sedimentary rocks Features of sedimentary rocks Strata or beds most characteristic Bedding planes separate strata May have important characteristics Size shape and distribution of grain sizes Fossils Sedimentary rocks Two main types Rocks formed by deposition of sediment Clastic Rocks formed by precipitation from water Chemical includes rocks formed by organisms Clastic Sediment Grains Particle loosened from pre existing rock Transported to place of deposition Shape size and sorting of grains can tell about the environment of deposition Lithification Process of becoming stone Burial and compaction Precipitation of cement Each reduces pore space Cement Brought in by water Mineral material between grains Fills in pore spaces Commonly calcite silica and sometimes iron oxide Bedding and bedding planes http www birdandhike com Hike General Info Glossary Gloss4 htm Types of Clastic Rocks Shale most abundant Sandstone Conglomerate Fossils Traces or remains of prehistoric life Are the most important inclusions Help determine past environments Used as time indicators Used for matching rocks from different places Shale with plant fossils Shale Composed of very fine grained sediment Shows obvious tendency to split along planes fissile Usually gray Most common type of sedimentary outcrop Sandstone Sandstone Composed of sand size particles Between 1 16 mm and 2 mm diameter Particles may be individual mineral grains or rock fragments Quartz most common type of grain Environments include Beach river shallow sea sand dunes Conglomerate Conglomerate Composed of particles larger than 2 mm Usually particles are rock fragments Clastic rocks Shale is the most common one Made from solid particles Classified by particle size Chemical rocks Material was once in solution and precipitates to form sediment Directly precipitated as the result of physical processes or Through life processes biochemical origin Chemical rocks Limestone Composed of the mineral calcite calcium carbonate Much of this calcite was precipitated by organisms Considered an organic chemical sediment if from organisms Most common type of chemical rock second most common type of sedimentary rock Chalk Fossiliferous limestone Coquina Close up of coquina Chemical rocks Direct mineral precipitation from water Evaporites such as rock salt or gypsum Microcrystalline quartz precipitated quartz known as chert flint jasper opal or agate Travertine calcite and sinter silica from hotspring deposits Travertine http njminerals org travertine html http www cis nctu edu tw whtsai World 20Highlig hts New 20Side 20Sho w 20Webpages imagepa ges Turkey 202001 Travertine 20stones 20 and 20water 20in 20P amukale html http www gonomad com destinations 0409 hot springs of the sierras html Evaporites http www bonnevillehealeyclub org http www img uni karlsruhe de 925 php http www pitt edu cejones GeoImages 1Mi nerals 2SedimentaryMineralz Gypsum html http www paintersflat net saltflat html http www flickr com photos snogun 191723596 http www nv blm gov Winnemucca blackrock BRHR Planning htm Rock salt http www mii org Minerals photochert html http geomaps wr usgs gov sfgeo geologic stories marin sedimentary html Chert http homestake sdsmt edu Photos Surface geology photos htm Classification of sedimentary rocks Features of sedimentary rocks Porosity Permeability Sedimentary rocks Economic importance Coal Petroleum and natural gas Precipitation of iron and aluminum Deposition of gold and tin Sand gravel clay Rock cycle diagram
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