III. Atoms, Elements and Minerals A. Changing scales to looking at the elements of the earth and its crust (8 most common) B. Introduction to minerals that comprise rocks (11 most common) C. The silicate minerals (7) D. Other important rock-forming minerals (4) E. Mineral properties

A. Changing Scale: Zooming in from global view to atomic scaleThe crust is made of rocks > Rocks are made of minerals >

A. Changing Scale: Zooming in from global view to atomic scaleRocks are made of minerals > Minerals are made of atoms

Atoms and ElementsNucleusProtons + Charge Has Mass, Atomic # Neutrons 0 Charge Mass same as One Proton Atomic Mass #ElectronsIn shells (2, 8, 8)- charge (balances each proton +)Very little Mass ElectronShellsSee Fig. 3-3, p. 56

IonsIncomplete electron shells tend to be filledE.g. Chlorine (Cl-)17 protons (at.# 17)17 electrons would make it neutral (no charge) with the last shell one electron short {2, 8, 7} SooooTends to grab an electron to fill the third shellMaking it a negatively charged Ion (anion)

IonsOther Common ExamplesSodium, at.# 11 {2, 8, 1} Na+

Oxygen, at.# 8 {2,6}, O-2

Silicon, at.# 14 {2,8,4} Si+4

(Cation)OxygenSodium

Most Common Elements of Earths Crust Oxygen:O-2 Silicon:Si+4 Aluminum:Al+3 Iron:Fe+2 or +3 Calcium: Ca+2 Sodium: Na+1 Potassium: K+1 Magnesium: Mg+2

Table 3-2, p. 63

Fig. 3-9, p. 62

B. Introduction to MineralsHalite (Rock Salt)Mineral mined for rock salt and table saltNa gives electron to ClOpposites attract, elements bondNaCl (Sodium Chloride)

*See Fig. 3-5, p. 57

Intro to MineralsRepeating 3-D pattern forms a Crystalline Solid (or Crystal)Naturally occurring crystals are MineralsDefinite Chemical composition (usually a range)Crystalline structure and bonding leads to physical properties: hardness, crystal form, cleavage, density (specific gravity )

3 planes of cleavageCrystal Form

Some Familiar Crystal FormsQuartz Crystal (SiO2)

Snow Flake (Ice Crystal) due to crystalline structure of H2OFig. 2.15a Fig. 3-2a, p. 55

Table 3-3, p. 63

Silica TetrahedraThe building block of most common rock forming mineralsFour O2- in a tetrahedral configurationOne Si4+ nested in the center(4 -2) +4 = -4(SiO4)-4See Fig. 3-10, p. 63

Silica TetrahedraThe building block of most common rock forming mineralsFour O2- in a tetrahedral configurationOne Si4+ nested in the center(4 -2) +4 = -4(SiO4)-4

Silica TetrahedraThe building block of most common rock forming mineralsFour O2- in a tetrahedral configurationOne Si4+ nested in the center(4 -2) +4 = -4(SiO4)-4

Silica TetrahedraThe building block of most common rock forming mineralsFour O2- in a tetrahedral configurationOne Si4+ nested in the center(4 -2) +4 = -4(SiO4)-4

Silica TetrahedraThe building block of most common rock forming mineralsFour O2- in a tetrahedral configurationOne Si4+ nested in the center(4 -2) +4 = -4(SiO4)-4

Silica TetrahedraThe building block of most common rock forming mineralsFour O2- in a tetrahedral configurationOne Si4+ nested in the center(4 -2) +4 = -4(SiO4)-4

Silica TetrahedraThe building block of most common rock forming mineralsFour O2- in a tetrahedral configurationOne Si4+ nested in the center(4 -2) +4 = -4(SiO4)-4

Silica TetrahedraThe building block of most common rock forming mineralsFour O2- in a tetrahedral configurationOne Si4+ nested in the center(4 -2) +4 = -4(SiO4)-4-4

C. Silica Tetrahedra and Silicate MineralsSi and O bond in a tetrahedron shapeThe basic building block of most minerals of the crustBond with other tetrahedra and cations to form Silicate Minerals

Fig. 3-11, p. 64

Silicate Minerals: ExamplesE.g., OlivineIsolated silicate structure(SiO4)-4 + 2Fe+2Fe2SiO4 Fe Mg SiO4

Mg2SiO4(Fe,Mg) 2 SiO4 Olivine Mineral GroupDefinite Range

Silicate Minerals: ExamplesE.g., OlivineIsolated silicate structure bonded with iron and magnesiumMakes up much of the mantleFe/Mg rich >50%Silica poor

Silicate Minerals: ExamplesE.g., Pyroxenes (Mineral Group)Single Chain Silicate structure (SiO3)-2 + Fe+2FeSiO3 (Fe,Mg) SiO3

MgSiO3(Fe,Mg) SiO3 Pyroxene Mineral Group Ferromagnesian

Silicate Minerals: ExamplesE.g., Pyroxenes (Group of minerals)Single Chain Silicate structure bonded with Fe, Mg, Ca, and AlFound in Oceanic CrustFe/Mg/Ca rich (20%)Silica poor (

Building SilicatesWhat is the net charge of:a silica tetrahedron?a single chain of single tetrahedra?

*Hint: a shared apex is an Oxygen

Building SilicatesWhat is the net charge of:a silica tetrahedron?a single chain of single tetrahedra?a double chain of tetrahedra?a sheet of tetrahedra?a framework of tetrahedra?a framework of tetrahedra with every fourth silicon replaced with an aluminum ion?a framework with every other Si replaced with an Al?

*Hint: a shared apex is an Oxygen

Building SilicatesWhat common elements would balance the charges of :an isolated silicate?a single chain silicate?a double chain silicate?a sheet silicate?a framework silicate?a framework of tetrahedra with every fourth silicon replaced with an aluminum ion?a framework with every other Si replaced with an Al?

Silicate Minerals: ExamplesE.g., Pyroxenes (Group of minerals)Single Chain Silicate structure bonded with Fe, Mg, Ca, and AlFound in Oceanic CrustFe/Mg/Ca richSilica poor *

Single Chain Silicates E.g., Pyroxenes (SiO3)

Silicate Minerals: ExamplesE.g., Amphiboles (Group of minerals)Double Chain Silicate structure bonded with Fe, Mg, Ca, and AlFound in Continental CrustMore silica and less iron than pyroxenes *

Double Chain SilicatesE.g., Amphiboles (Si8O22)

Silicate Minerals: ExamplesE.g., Micas (Muscovite and Biotite)Sheet Silicate structure bonded with Al, K, (biotite has Fe, Mg) Found in Continental CrustMore silica and less iron than Amphiboles E.g., Clays (Mineral Group)Hydrated, sheet silicates from weathering of other silicates *

Sheet SilicatesE.g., Micas (Biotite and Muscovite) (AlSi3O10)

Fig. 3-12a, p. 65

Silicate MineralsE.g., Feldspars (Orthoclase and Plagioclase) and QuartzFramework Silicatebonded with Al, and K (orthoclase) or Na-Ca (plagioclase)Found in Continental CrustMore silica than micas, no iron GraniteOrthoclaseQuartz*

Framework SilicatesE.g., Quartz (SiO2) and Feldspars (AlSi3O8)

Framework SilicatesE.g., Quartz (SiO2) and Feldspar (AlSi3O10)

Fig. 3-12b, p. 65

Figure 3.9: Electrical charges and relative sizes of ions common in minerals. The numbers inside the ions are the radii shown in angstrom units (1 = 1010 m).Active Figure 3.11: Structures of some of the common silicate minerals shown by various arrangements of silica tetrahedra. (a) Isolated tetrahedra. (b) Continuous chains. (c) Continuous sheets. (d) Networks. The arrows adjacent to single-chain, double-chain, and sheet silicates indicate that these structures continue indefinitely in the directions shown.Figure 3.12a: Examples of the common ferromagnesian silicates olivine, the pyroxene-group mineral augite, the amphibole-group mineral hornblende, and biotite.Figure 3.12b: The nonferromagnesian silicates quartz, the potassium feldspar orthoclase, plagioclase feldspar, and muscovite.