I Minerals the building blocks of rocks A Definition of mineral 1 Naturally occurring 2 Inorganic 3 Solid 4 Possess an orderly internal structure of atoms 5 Have a definite chemical composition B Rocks are aggregates mixtures of minerals or mineral like material coal is a rock II Composition and structure of minerals A Elements 1 Basic building blocks of minerals 2 More than 100 are known 3 eight most common elements in Earth s crust oxygen silicon aluminum iron calcium sodium potassium magnesium III Properties of minerals 1 Crystal form growth surfaces external expression of internal arrangement 2 Luster reflection of light ALL minerals have a luster 3 Color may be created by minor impurities 4 Streak more diagnostic in identifcation 5 Hardness resistance to scratching may be affected by alteration 6 Cleavage parallel planes of breakage determined by strength of internal bonds there may be intersecting sets in some minerals 7 Fracture description of breakage when there is no cleavage 8 Specific gravity comparison to an equal volume of water heft 9 Other properties a Taste b Smell c Elasticity d Malleability e Feel f Magnetism g Double refraction h Reaction to hydrochloric acid IV About 25 minerals are A called the rock forming minerals 1 Feldspars quartz micas pyroxenes amphiboles olivine calcite gypsum dolomite iron oxides pyrite garnet 2 The eight elements that compose most rock forming minerals are oxygen O silicon Si aluminum Al iron Fe calcium Ca sodium Na potassium K and magnesium Mg 3 The most abundant atoms in Earth s crust are a Oxygen 46 6 by weight b Silicon 27 7 by weight B Mineral groups 1 Silicates a Most common mineral group because O Si most common b Contain the silicon oxygen tetrahedron 1 Four oxygens surrounding a much smaller silicon atom 2 The silica tetrahedra join together in a variety of ways a Framework b Sheet c Chains single chains and double chains c Feldspars are the most plentiful group framework silicate d Most silicate minerals crystallize from magma as it cools 2 Non silicate minerals a Major groups 1 Oxides 2 Sulfides 3 Sulfates 4 Halides 5 Carbonates 6 Native elements b Carbonates 1 Major rock forming group 2 Found in limestone and marble c Halite and gypsum found in sedimentary rocks d Many have economic value V The rock cycle Inter relationship of parts of Earth system 1 Three types a Igneous crystallized from magma b Sedimentary deposited by deposition or precipitation c Metamorphic changed in the solid state 2 cycle discussion can start at any position a usually at the molten magma 1 magma mostly Si O 2 minor amounts of Al Fe Ca Na K Mg b crystallizes to form silicate minerals igneous rocks 1 intrusive cooling slowly below surface coarse grained 2 extrusive cooling quickly at or near surface fine grained c exposure at surface results in weathering 1 breaks down minerals chemically and physically a different temperature and pressure than formed b action of water a universal solvent 2 becomes sediment that is deposited d sediment is lithified by compression and cementation e addition of heat and pressure can cause atoms to reform into different minerals or different grain sizes 1 without melting 2 metamorphism metamorphic rock is formed f other paths exist across the cycle 1 igneous or metamorphic rocks can be metamorphosed 2 sedimentary or metamorphic rocks can be weathered 3 if there is melting the only route is magma igneous VI Sedimentary rocks A Rock cycle 1 magma solidifies into igneous rock 2 Surface processes weather rock deposited as sediments any rock type can be weathered 3 sediment is lithified by compaction and cementation 4 heat and pressure of burial change rock mineralogy in solid state to create metamorphic rock any type can be metamorphosed 5 enough heat pressure can cause melting magma B Features of sedimentary rocks 1 sedimentary rocks can preserve Earth surface features a evidence of past life on Earth fossils b on deposition surface showing environment of formation 1 desiccation cracks 2 ripple marks 2 Strata or beds a most characteristic feature of sedimentary rocks b bedding planes separate strata 3 Fossils a Traces or remains of prehistoric life b Are the most important inclusions c Help determine past environments d Used as time indicators e Used for matching rocks from different places 4 Porosity and permeability a Hold fluids such as petroleum or water b Receive ore deposits by precipitation from fluids VII Formation of sedimentary rocks 1 settles out of a fluid a deposition of solid particles b precipitation of minerals from water c formed by organisms in one of the two above processes 2 weathered debris carried by fluid a running water b wind c ice 3 formed at surface so most rocks exposed at surface are sedimentary about 75 of all rock outcrops on the continents 4 Used to reconstruct much of Earth s history a Clues to past environments sediment transport b often contain fossils indicating environment and age 5 Economic importance a Coal Petroleum and natural gas b Chemical precipitation of iron and aluminum c Mechanical deposition of gold tin garnet d Sand gravel clay for construction and industry 6 Classifying sedimentary rocks a Two major divisions 1 Made of particles clastic or detrital 2 Minerals precipitating from water chemical 3 Most rocks are combinations but many are predominantly one or the other VIII Clastic sedimentary rocks 1 from preexisting rock a Transported and rounded to place of deposition b Shape size and sorting of clasts tells a tremendous amount about the environment of deposition 1 Particle size named by fraction of mm a Over 2 mm gravel b 1 16 to 2 mm sand c 1 256 to 1 16 mm silt 1 28 d Less than 1 256 mm clay 2 Sorting refers to the range of sizes present c Deposition of sediment puts in a place to become lithified process of becoming stone 1 Burial and compaction 2 Precipitation of cement a Brought in by water b Mineral material between clasts c Fills in pore spaces d Calcite silica and sometimes iron oxide 3 Each reduces pore space 2 Types of clastic rocks a Shale most abundant 1 Composed of very fine grained sediment 2 Tendency to split along planes fissile 3 Usually gray 4 Most common type of sedimentary outcrop b Sandstone 1 Composed of sand size particles 2 Between 1 16 mm and 2 mm diameter 3 Individual mineral grains or rock fragments 4 Quartz most common type of grain 5 Environments include c Conglomerate 1 Composed of particles larger than 2 mm 2 Usually particles are rock
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