1Essentials of GeologyEssentials of GeologyDavid SalleeDavid SalleeChapter 2Chapter 2Minerals:Minerals:Building Blocks Building Blocks of Rocksof RocksMatterMatter--What is it and What What is it and What Does it Consist of?Does it Consist of?Elements and AtomsElements and Atoms••Elements cannot be Elements cannot be split into split into substances of substances of different different composition. They composition. They are composed of are composed of atoms, the smallest atoms, the smallest particle that still particle that still retains the retains the properties of the properties of the element.element.••Atoms consist of :Atoms consist of :Protons, Neutrons, & Protons, Neutrons, & ElectronsElectronsMatterMatter--What is it and What is it and What Does it Consist of?What Does it Consist of?Protons: have a positive charge and contribute massProtons: have a positive charge and contribute mass••located in the nucleuslocated in the nucleusElectrons: have a negative charge and little massElectrons: have a negative charge and little mass••orbit the nucleus in shellsorbit the nucleus in shellsNeutrons: electrically neutral, found in the nucleusNeutrons: electrically neutral, found in the nucleusIsotopes: atoms with varying numbers of neutronsIsotopes: atoms with varying numbers of neutronsBonding and CompoundsBonding and CompoundsCompounds are formed Compounds are formed by the bonding of two or by the bonding of two or more atoms.more atoms.Ionic BondingIonic BondingThe electron in the The electron in the outermost shell of outermost shell of sodium is transferred to sodium is transferred to the outermost shell of the outermost shell of the chlorine atom. Once the chlorine atom. Once the transfer is made, the the transfer is made, the atoms are positively and atoms are positively and negatively charged ions.negatively charged ions.Bonding and CompoundsBonding and CompoundsCovalent BondingCovalent BondingFormed by adjacent atoms sharing electrons in diamond Formed by adjacent atoms sharing electrons in diamond and graphite. Van and graphite. Van derderWaalsWaalsbonding between sheets of bonding between sheets of covalently bonded carbon atoms are weak, while the covalently bonded carbon atoms are weak, while the sheets themselves are strong. Metallic bonding results sheets themselves are strong. Metallic bonding results from extreme electron sharing.from extreme electron sharing.2What are Minerals?What are Minerals?Naturally Naturally OccurringOccurringInorganicInorganicCrystalline SolidsCrystalline SolidsNarrowly defined Narrowly defined chemical chemical compositioncompositionCharacteristic Characteristic Physical Physical propertiespropertiescalcitecalciteWhat are Minerals?What are Minerals?Mineral Mineral CrystalsCrystals••Can occur in Can occur in a variety of a variety of shapes which shapes which reflect the reflect the orderly orderly internal internal arrangement arrangement of atoms.of atoms.What are Minerals?What are Minerals?••Shown by a Shown by a chemical formula chemical formula such as NaCl or such as NaCl or SiOSiO22(Halite, (Halite, Quartz)Quartz)••A range of A range of compositions may compositions may be indicated as in be indicated as in (Mg,Fe)(Mg,Fe)22SiOSiO44(Olivine), where (Olivine), where either either magnesium, iron, magnesium, iron, or a combination or a combination of both make up of both make up the molecular the molecular structurestructureChemical Composition of MineralsChemical Composition of MineralsHow Many Minerals are How Many Minerals are Known?Known?More than 3,500 More than 3,500 identifiedidentified••Less than 25 are Less than 25 are common as rock common as rock forming mineralsforming minerals••They are They are composed of the composed of the most abundant most abundant elements found elements found in the crustin the crustMost abundant Most abundant elements in the crust elements in the crust (% weight)(% weight)••OxygenOxygen--46.646.6••SiliconSilicon--27.727.7••AluminumAluminum--8.18.1••IronIron--5.05.0••CalciumCalcium--3.63.6••SodiumSodium--2.82.8••PotassiumPotassium--2.62.6••MagnesiumMagnesium--2.12.1••all othersall others--1.51.5Mineral Groups Recognized Mineral Groups Recognized by Geologistsby GeologistsThe Silicate MineralsThe Silicate Minerals••Built from the two most abundant elements in the Built from the two most abundant elements in the earth’s crust, atoms are arranged in a earth’s crust, atoms are arranged in a tetrahedron, with oxygen atoms at the four tetrahedron, with oxygen atoms at the four corners.corners.••The silica tetrahedron is the basic building block The silica tetrahedron is the basic building block for all the silicate minerals.for all the silicate minerals.Mineral Groups Mineral Groups Recognized by GeologistsRecognized by GeologistsSilicatesSilicatesSilica Silica tetrahedratetrahedracombine with combine with positively charged positively charged ions or share ions or share electrons. The electrons. The result of different result of different bonding bonding possibilities possibilities produce the produce the silicate structures silicate structures shown .shown .3Mineral Groups Mineral Groups Recognized by GeologistsRecognized by GeologistsNonferromagnesianNonferromagnesiansilicatessilicatesgenerally light in color,generally light in color,lower densitylower densityFerromagnesian Ferromagnesian silicatessilicatesgenerally dark in generally dark in color, color, higher densityhigher densityMineral Groups Mineral Groups Recognized by GeologistsRecognized by GeologistsCarbonate MineralsCarbonate Minerals••Contain the negatively Contain the negatively charged carbonate ion charged carbonate ion (CO(CO33))--22, which bonds , which bonds with a positively with a positively charged ioncharged ion••Common carbonates Common carbonates are calcite (CaCOare calcite (CaCO33), ), and dolomite and dolomite [CaMg(CO[CaMg(CO33))22], the ], the predominant minerals predominant minerals in the sedimentary in the sedimentary rocks limestone and rocks limestone and dolostonedolostoneMineral Groups Mineral Groups Recognized by GeologistsRecognized by GeologistsOther Mineral Other Mineral GroupsGroups••Oxides Oxides (Fe(Fe22OO33))••Sulfides Sulfides ((PbSPbS))••Sulfates Sulfates (CaSO(CaSO44··2H2H22O)O)••Halides Halides