Minerals and rocks

Minerals and Rocks Lecture Outline  What are minerals?  Common rock-forming minerals  Physical properties of minerals  Basic rock types  The rock cycle Minerals A mineral is a naturally occurring, solid crystalline substance, generally inorganic, with a specific chemical composition Natural Solid Atoms arranged in orderly repeating 3D array: crystalline Not part of the tissue of an organism Composition fixed or varies within defined limits Minerals are the “building blocks” of rock Click to edit Master text styles Second level Third level Fourth level Fifth level Large individual crystals (rare) Mass of small grains: each is a crystal, but grown up against each other Atomic Structure of Minerals NaCl - sodium chloride Halite Chemical Bonds: Ionic  Electrical attraction between ions of opposite charge  Bond strength increases with the electrical charges of the ions  Bond strength decreases as the distance between the ions increases  Most minerals are this kind of compound Ionic Bonding example: halite Cation Na+ Anion Cl- Covalent Bonds: Electron sharing Generally stronger than ionic bonds (e.g., diamond) Crystallization of Minerals  Need starting material with atoms that can come together in the proper proportions  Growth from a liquid or a gas  Time and space for crystallization  Appropriate temperature and pressure  Examples  Magma that has cooled below its melting point  Supersaturated solution > precipitation Crystallization of Minerals  Crystals begin as an initial “seed” - a microscopic crystal  Atoms keep being added in a 3D array, repeating the basic arrangement  Crystal faces are based on the array structure granite Click to edit Master text styles Second level Third level Fourth level Fifth level gneiss Click to edit Master text styles Second level Third level Fourth level Fifth level Click to edit Master text styles Second level Third level Fourth level Fifth level Click to edit Master text styles Second level Third level Fourth level Fifth level Click to edit Master text styles Second level Third level Fourth level Fifth level The Rock Cycle The Rock Cycle Click to edit Master text styles Second level Third level Fourth level Fifth level Click to edit Master text styles Second level Third level Fourth level Fifth level Click to edit Master text styles Second level Third level Fourth level Fifth level [...]... those large anions  Various cations can substitute for each other in many minerals  Same crystal structure  Different chemical composition Click to edit Master text styles Second level Third level Fourth level Fifth level Polymorphs Minerals with the same composition, but different crystal structure Common Rock-Forming Minerals Minerals fall into a small number of related “families” based mainly on... Sulfates  Minerals with sulfate ion (SO42-)  Gypsum (CaSO4.H2O), anhydrite (CaSO4) Click to edit Master text styles Second level Third level Fourth level Fifth level Gypsum Gypsum Cave of the Crystals • 1,000 feet depth in the silver and lead Naica Mine • 150 degrees, with 100 % humidity • 4-ft diameter columns 50 ft length Identification of Minerals  Chemical composition (microprobes and wet chemical... tetrahedra can combine in several ways to form many common minerals  Typical cations: K+, Ca+, Na+, Mg2+, Al3+, Fe2+ Different numbers of oxygen ions are shared among tetrahedra Carbonates  Cations with carbonate ion (CO32-)  Calcite (CaCO3), dolomite (CaMg(CO3)2), siderite (FeCO3), smithsonite (ZnCO3)  Make up many common rocks including limestone and marble  Very important for CCS! Calcite (CaCO3)...Cations and Anions  Anions are typically large  Cations are relatively small  Crystal structure is determined largely by the arrangement of the anions Common cations and anions Click to edit Master text styles Second level Third level Fourth level Fifth level Radii given in angstroms; 10-8 cm Ions can be compound  So far, we’ve talked about individual atomic ions  Many common minerals are... level Fourth level Fifth level Silicates Most abundant minerals in the Earth's crust Silicate ion (tetrahedron), SiO44-  Quartz (SiO2), K-feldspar (KAlSi3O8), olivine ((Mg, Fe)2SiO4), kaolinite (Al2Si2O5(OH)4) Quartz (SiO2) Click to edit Master text styles Second level Third level Fourth level Fifth level Silicate structure  Most of the most common rocks in the crust are silicates  Silicate tetrahedra... level Fourth level Fifth level CaCO3 + 2H+ = Ca2+ + CO2 + H2O Click to edit Master text styles Second level Third level Fourth level Fifth level Smithsonite (ZnCO3) Oxides  Compounds of metallic cations and oxygen  Important for many metal ores needed to make things (e.g., iron, chromium, titanium)  Ores are economically useful (i.e., possible to mine) mineral deposits Click to edit Master text styles