Minerals, rock cycle Page 1 of 4 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 B. Atoms 1.Smallest particles of matter 2.Have all the characteristics of an element III. Structure of atoms A. Nucleus contains 1.Protons—positive electrical charge 2.Neutrons —electrically neutral B. Energy levels, or shells of electrons 1.Surround nucleus 2.negative electrical charge C. Atomic number, the number of protons in an atom's nucleus, identifies element D. Bonding of atoms 1.Compounds are formed from two or more elements 2.Ions are atoms that have gained or lost electrons E. Isotopes 1.Vary in the number of neutrons—same number of protons 2.Have different mass numbers—the sum of the neutrons plus protons 3.Radioactive isotopes a. Unstable b. emit energy and particlesMinerals, rock cycle Page 2 of 4 IV. Minerals A. 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 B. About 25 minerals are 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) C. 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 coolsMinerals, rock cycle Page 3 of 4 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 A. 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→igneousMinerals, rock cycle Page 4 of 4 II. Sedimentary rocks A. Formed of particles transported by, or crystallization from, water 1. two major classification: detrital (or clastic), and chemical 2. detrital sedimentary rocks from particles of pre-existing rocks a. classified by particle size 1) gravel—conglomerate or breccia 2) sand—sandstone 3) mud—shale or siltstone b. range of size of particles implies environment of formation 3. chemical sedimentary rocks a. limestone composed of calcite 1) calcite often precipitated by organisms as shell or ‘test’ 2) some directly from concentrated solution—especially in caves or from hot springs b. silica can form from solution in deep sea, and in hot springs c. evaporation of surface water leads to ‘evaporite’ deposits 1) halite most common—Na, Cl in high in sea water 2) gypsum also from sea-water: Ca, SO4 4. third ‘oddball’ classification is “organic” a. coal is organic sedimentary rock b. some limestones may be classified here too 5. 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 III. Metamorphic rocks A. Change in the solid state by heat and pressure 1. change of grain size or shape 2. rearrangement of atoms into different minerals 3. parent rock, and various amounts of heat and amounts of pressure result in wide variety of metamorphic rocks a. slate, schist, gneiss b. quartzite, marble B. high pressure, temperature allows rock to flow from directed stress IV. Tectonic setting of rocks A. Convergent plate boundaries create directed pressure and intermediate and felsic magma 1. metamorphic rocks grades depend on depth/lateral position 2. andesite volcanic rocks and granite intrusive rocks B. divergent plate boundaries create basalt, gabbro, ultramafic rocks C. where continental-to-oceanic lithosphere is not on an active
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