1Earth Materials: Minerals• What is a mineral?• Properties/characteristics of different types of minerals1• Mineral structures and bonding• Major categories of minerals• Importance and uses of mineralsWhat is a mineral?Requirements for something to be considered a mineral:2- naturally occurring- inorganic- solid- crystalline- contains specific composition of elementsMineral PropertiesThree general categories:Optical3PhysicalChemicalMineral PropertiesSome optical propertiesColorStreak4StreakLusterDouble refractionFluorescenceTransmission of light (transparent, translucent, or opaque)2Minerals of various colorsUnderstanding Earth5StreakExample: hematiteFig 2.26 Understanding Earth6Metallic luster: gold and pyrite7Non-metallic luster: feldspar, mica, olivine, and quartzDouble refraction in a transparent piece of calcite83Mineral PropertiesSome physical propertiesHardness 9DensityCrystal shapeHow it breaks: cleavage and fracture10Understanding Earth11Crystal of galena (left) (lead sulfide)Crystal of quartz (right) (silicon dioxide)Galena, which contains lead, is much more dense than quartz.The two minerals also have different crystal shapes.Fig 2.10 Understanding EarthMineral PropertiesHow a mineral breaks:Fracture- when a mineral breaks along irregular surfaces- any mineral may exhibit fracture- some particular types of fracture have names: irregular (rough with no particular pattern) conchoidal (with smooth curved surfaces like12with no particular pattern), conchoidal (with smooth, curved surfaces like glass), fibrous or splintery (similar to broken wood), etc.Cleavage- when a mineral breaks along flat, planar surfaces- some minerals have cleavage & others do not- key observations:- numberof different cleavage directions- anglebetween cleavage directions413Conchoidal fracture in obsidianFig 4.3 Understanding Earth14Cleavage of mica into thin sheetsFig 2.23 Understanding EarthCleavage in calciteFig 2.24 Understanding Earth15Cleavage anglesFig 2.25 Understanding Earth165Mineral PropertiesChemical propertiesAcid test Salty taste Many other chemical tests17Acid test for calciteFig 2.22 Understanding EarthMineral PropertiesSome other propertiesHabitMti18Magnetism Absorbs waterSmellSome unusual crystalHabitsGeology2ndedbarite rosettes(barium sulfate)needles of stibnite(antimony sulfide)19Geology2ed.Chernicoffstellate pyrite(iron sulfide)botryoidal malachite (green) with azurite (blue)(hydrous copper carbonates)Fibers of chrysotile(one type of asbestos)Chapter 2 Understanding Earth206In-class exercise21Working in groups, examine and describe the properties of each mineral sample providedMineral PropertiesRelationship to:22atomic compositionatomic structure and bondingMineral PropertiesChemical bonds - how multiple atoms are held togetherionic- attraction between ions of opposite electrical charge- example: Na+ and Cl- ions combine to form halite- the most common type of bonding in mineralscovalent23covalent- sharing of electrons between atoms- the strongest type of chemical bond- metals have a particular type of covalent bond called a metallicbondother types of bondinge.g. van der Waalsbonds, a very weak type of bonding24Graphite and DiamondBoth are composed of carbon but have very different properties. Fig 2.15 Understanding Earth7Carbon atomFig 2.2 Understanding Earth25Structures of26Structures of graphite (left) and diamond (right)Geology 2nded. - ChernicoffStructure of halite (sodium chloride -salt)Fig 2.16 Understanding Earth27Ionic bonds hold together Cl -1and Na +128Regular arrangement of atoms in galena (left)Cube-shaped crystals (below)The structure of galena is essentially the same as in halite. Therefore, both grow and break to form cubes. Their color and luster are different, however, because they have different compositions (and bonding).Fig 2.10 Understanding Earth8Understanding Earth29Some major groups of mineralsSilicates e.g. quartz, feldspar, mica, olivineNon-silicates:Carbonatese.g. calcite30Carbonatese.g. calciteOxides e.g. magnetite, hematiteSulfides e.g. pyrite, galenaSulfates e.g. gypsumNative elements e.g. native gold, copperHalides e.g. halite31Silicon-oxygen tetrahedronFig 2.16 Understanding Earthildoublesheets32Types of silicate mineral structuresFigs 2.17 and 2.18 Understanding Earthindividualtetrahedrasingle chainsdouble chainssheets3-D frameworks9Mica is built from numerous sheets. This explains the single direction of cleavage found in micas.33Geology 2nded. - ChernicoffMuscovite MicaImportance of Minerals• Almost all rocks are made of minerals!• Aesthetic value • Gemstones•museum specimens34•museum specimens• Natural resource value• source of metals needed for electronics manufacture, cars, airplanes, etc.• raw materials for making window glass, plaster/sheetrock, etc.Minerals in GraniteMinerals as Constituents of Rocks35Alkali Feldspar(Orthoclase)Amphibole(Hornblende)QuartzPlagioclase feldspar, Muscovite mica, and Biotite mica also may be found in some granitesNative goldSmithsonianAesthetic valueA large cut diamondSmithsonian361037Iron oresmagnetite, iron+oxygen (left) pyrite iron+sulfur (right)siderite iron+carbon+oxygen (top) hematite iron+oxygen (bottom)Fig 22.10 Understanding EarthA great deal of effort goes into obtaining key mineral resources38Open pit copper mine south of Tucson, ArizonaFig 22.22 Understanding EarthU.S. reliance on imported mineral resourcesFig 22.17 Understanding Earth39U.S. reliance on imported mineral resourcesFig 22.17 Understanding Earth4011Some Online ResourcesMineral resources info. from the USGShttp://minerals.er.usgs.gov/http://minerals.er.usgs.gov/minerals/http://www.usgs.gov/science/science.php?term=745WebMineral Minerals Databasehttp://www.webmineral.com/MinDat Minerals Databasehttp://www mindat org/41http://www.mindat.org/Smithsonian Gem & Mineral Collectionhttp://www.gimizu.de/sgmcol/Smithsonian Department of Mineral Scienceshttp://www.minerals.si.edu/More rock and mineral links (some with lesson plans)http://edtech.kennesaw.edu/web/rocks.htmlhttp://www.dlese.org/dds/browse_su_0k.htm (Digital Library for Earth System