MineralsASTS - Minerals Earth's Building Blocks Why study...

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Unformatted text preview: Minerals Earth's Building Blocks Why study minerals? Rocks are made of Minerals Minerals are resources Mineral hazards Pb History of the Earth (age dating) **How the earth works Composition of the crust crust has a different composition than whole earth Less dense More silica (SiO2) Less iron, nickel elements arranged into molecules called minerals Chemistry Review Everything is made of atoms Atom "individible" Atoms/elements are made of A single unit of an element Protons (Z) Neutrons (N) Electrons Elements are named based on their number of protons All elements exist on Periodic Table Ions, atoms with a charge Cation Positive charge Too few electrons Anion Negative charge Attraction and bonding occurs between cations and anions Common ions in minerals (and rocks): Too many electrons O Oxygen (2) Si Silicon (+4) Ca Calcium, Mg Magnesium (+2) Fe Iron (+2 or +3) Bonding If two or more atoms share electrons, they make a bond Example NaCl Ionic bond Other types of bonds: Metallic Covalent Temperature and bonds Temperature (T) is a measure of heat Heat is a form of energy When molecules collide, they release heat which increases T Because heat is energy, heat creates movement increase T, increase motion Heat from the environment causes molecules to vibrate Increasing temperature breaks bonds Ways to increase temperature Convection Conduction Molecules vibrate Increase kinetic energy & heat up Material moves Heat transferred with it Marshak (2004, Fig. a.17) What is a mineral? Homogenous Naturally occurring Solid Inorganic substance Definable composition Orderly arrangement of atoms in a lattice What is a mineral? Homogenous: Naturally occurring Same throughout Can not be broken into simpler components Form by natural process Not made by humans If produced in a lab, substances are refered to as synthetic minerals Synthetic minerals are not as valuable as true minerals Synthetic gems are "fakes" What is a mineral? Solid Definite shape and volume Gas, liquids adapt shape of container Solids hold shape unless deformed by external force Shape formed by longrange bonds in solid Not liquid Or gas What is a mineral? Orderly arrangement of atoms in lattice Fixed in specific pattern that repeats Framework is called a crystal lattice Minerals are Crystaline Disordered atoms: Random pattern Crystalline atoms: Organized pattern that repeats What is a mineral? Inorganic substance Do not contain organic chemicals Organic chemical Carbon bonded to hydrogen along with oxygen, nitrogen, and other elements Examples: gain alcohol, oil, gasoline Minerals can contain carbon Examples What is a mineral? Definable chemical composition It is possible to write a chemical formula Formula either fixed or varies within limits Constant Composition Quartz SiO2 Hematite Fe2O3 KFeldspar KAl Si3O8 Olivine (Fe,Mg)2SiO4 Plagioclase NaAlSi3O8CaAl2Si2O8 Hornblende (Ca,Na) Variable Composition Mineral Properties Traits or descriptions of minerals Diagnostic Properties properties that tend to be unique to a subclass of minerals Types of properties Used to distinguish one mineral from another Many need several to properly identify a mineral Hardness Cleavage/facture Luster Color Specific gravity Crystal habit What is a mineral? Definable composition Orderly arrangement of atoms in a lattice Homogenous Naturally occurring Solid Inorganic substance Mineral Classes Way of grouping and organizing minerals Based primarily on chemistry Silicates Most common in the crust Contain Silicon (Si) and Oxygen (O) Oxides Consist of metal bonded to oxygen Often mined for metal content Sulfides Metal bonded to sulfide (S2) Often considered ore minerals Sulfates Metal bonded to sulfate (SO 2) 4 Form by precipitation Halides Contain halogen ions (Cl, F) Form by precipitation Carbonates Contain carbonate (CO 2) 3 Native Metals Pure masses of metal not bonded to anion Gold (Au), Silver (Ag), Cooper (Cu) Silicate ion (SiO44) The silicate ion forms tetrahedra. Silicate ion (SiO44) The silicate ion forms tetrahedra. Oxygen ions (O2) Silicon ion (Si4+) Tetrahedra can arrange in other ways. Mineral Chemical formula Cleavage planes and number of cleavage directions 1 plane Silicate structure Isolated tetrahedra Specimen Olivine (Mg, Fe)2SiO4 2 planes at 90 Pyroxene (Mg, Fe)SiO3 Single chains 2 planes at 60 and 120 Amphibole Ca2(Mg, Fe)5Si8O22(OH)2 Double chains 1 plane Micas Muscovite: KAl2(AlSi3O10)(OH)2 Biotite: K(Mg, Fe)3AlSi3O10(OH)2 2 planes at 90 Feldspars Orthoclase feldspar: KAlSi3O8 Plagioclase feldspar: (Ca, Na) AlSi3O8 Sheets Threedimensional framework Minerals & Environmental Geology Mineral Resources "If it can't be grown, it must be mined" Metals, rocks, energy resources Mining Hazards Local environmental damage Acid mine drainage Deforestation Runoff Mineral Hazards Asbestos Silica Something to think about... There are over 3500 different minerals, each with a name, distinctive physical properties, and distinctive structure and/or composition The unique physical properties of a mineral are due to its chemical composition and crystal structure. ...
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This note was uploaded on 04/17/2008 for the course GEO unk taught by Professor J.popo during the Spring '08 term at DePauw.

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