Geology 114 Lecture Notes

 

Introduction

Read Chapter 1 of Nesse

atoms → molecules → crystals → rocks → Earth

 see http://darkwing.uoregon.edu/~cashman/GEO311/311pages/L1-Intro_pic_files/image014.gif

 

Strategic Minerals and Metals

Atoms and Elements

Read Chapter 3 of Nesse

 

Element: A form of matter than cannot be broken down by conventional heating or cooling

 

Common mineral-forming elements

Elemental composition of the whole Earth and the crust (the outermost solid layer):

element

whole Earth

crust

mineral

O

29%

46%

most minerals

Si

15%

28%

silicates

Al

1%

8%

feldspar

Fe

35%

6%

pyroxene, amphibole

Ca

1%

4%

plagioclase

Na

<1%

2%

feldspar

Mg

11%

2%

olivine

K

<1%

2%

K-feldspar

S

<3%

<1%

pyrite

Ni

2%

<1%

olivine

 

composition of Earth’s crust




the arrangement of elements in columns relates to the similarities in their chemical behavior:

noble gases

halogens

metals

alkaline earth metals

alkali metals

 

 

Atoms

 

nucleus

Atom: The smallest particle that retains the chemical properties of an element; composed of (isotopes are atoms, but every isotope is not an element)
proton: electric charge +1, 1.00728 amu

neutron: electric charge 0, 1.00867 amu

electron: electric charge –1, 0.00055 amu (insignificant)

For example, Li has an atomic number of 3, meaning 3 protons (and 3 electrons, if neutral); if it is 7Li, it has a mass of 7 and thus 4 neutrons
electrons fill orbital levels around the nucleus: 2 in the first level, 8 in the second, and so on
the position of an element in the periodic table relates to the number of electrons in the outer orbital

 

 

Structure of Atoms

The four electron shells surrounding the nucleus are named—with increasing distance and energy—K, L, M, and N shells. Each shell is split into subshells, labeled s, p, d, and f. An s subshell consists of one s orbital (with 2 electrons), a p subshell consists of up to 3 p orbitals (6 electrons), and a d subshell consists of up to 5 d orbitals (10 electrons).

 

 

                                                                shell

(±)                 K         L         L         M        M        M        N         N

Z   element  1s        2s        2p       3s        3p       3d       4s        4p

1          H         1                                                                                 

2          He      2          (1 shell is full)                                                                 

 

3          Li         2          1                                                                     

4          Be        2          2                                                         

5          B          2          2          1                                                         

6          C          2          2          2                                                         

7          N         2          2          3                                                         

8          O         2          2          4                                                         

9          F          2          2          5                                                         

10       Ne       2          2          6          (2 shell is full)                                         

 

11        Na       2          2          6          1                                             

12        Mg      2          2          6          2                                             

13        Al        2          2          6          2          1                                 

14        Si         2          2          6          2          2                                 

15        P          2          2          6          2          3                                 

16        S          2          2          6          2          4                                 

17        Cl         2          2          6          2          5                                 

18       Ar       2          2          6          2          6          (3 shell is full)                 

 

19        K         2          2          6          2          6                      1         

20       Ca        2          2          6          2          6                      2

21        Sc        2          2          6          2          6          1          2         

22        Ti        2          2          6          2          6          2          2         

23        V         2          2          6          2          6          3          2         

24        Cr        2          2          6          2          6          4          2         

25        Mn      2          2          6          2          6          5          2         

26        Fe        2          2          6          2          6          6          2         

27        Co        2          2          6          2          6          7          2         

28        Ni        2          2          6          2          6          8          2         

29        Cu       2          2          6          2          6          9          2         

30       Zn       2          2          6          2          6          10        2         

 

31        Ga       2          2          6          2          6          10        2          1

32        Ge       2          2          6          2          6          10        2          2

33        As        2          2          6          2          6          10        2          3

34        Se        2          2          6          2          6          10        2          4

35        Br        2          2          6          2          6          10        2          5

36       Kr       2          2          6          2          6          10       2          6          (4 shell is full)     

 

Ions

elements tend to gain or lose electrons to acquire the configuration of a noble gas

cation: ion w/ excess + charge

anion: ion w/ excess — charge

typical oxidation states: http://www.wsu.edu/~wherland/#Radii or http://en.wikipedia.org/wiki/Ionic_bond

this propensity was termed electronegativity by Linus Pauling; e.g., Li has an electronegativity of 1 and F is 4

 

Cosmochemistry and the production of elements

 (for more see http://en.wikipedia.org/wiki/Stellar_nucleosynthesis)

The birth of matter in the universe began about 13.7 Ga, judged by tracing expanding galaxies (groups of stars) back to a common origin in the Big Bang.
After 1 m.y., the universe had cooled sufficiently (3000K) for H and He to form from subatomic particles.
These elements aggregated to form stars via gravitational attraction after 200 Myr; stars are 75 wt% H, 22 wt% He, and 3% heavier elements.

Carbon burning

12C + 12C –> 20Ne or 23Na or 23Mg or 24Mg or 16O

carbon is consumed and a core of product elements builds up; gravity builds up and the new core collapses sufficiently to burn heavier elements

 

Oxygen burning

16O + 16O –> 28Si or 31P or 31S or 30Si or 30P or 32S or 24Mg

O, Ne, Mg, Si, S burning takes a star 6 months, reaching 3E9 Kelvin

 

The heat of star aggregation caused particles and elements to accelerate and collide, forming elements as heavy as Fe (atomic number 26).

Silicon burning

lasts one day, reaching 5E9 Kelvin. This causes a gravitational collapse, forming either a neutron star or a black hole, with the outer layers being blown off in a supernova whose neutron burst forms elements heavier than Fe

28Si + 4He –> 32S

32S + 4He –> 36Ar

36Ar + 4He –> 40Ca

40Ca + 4He –> 44Ti

44Ti + 4 He –>48Cr

48Cr + 4He –> 52Fe

52Fe + 4He –> 56Ni

 

Elements heavier than Fe are produced by during supernovae explosions, which occur when the gravitational force of the outer layers of a star overcomes the thermal pressure of the fusing inner layers.

 

Further accretion formed solar systems, meteorites, and planets by about 4.5 Ga
Differentiation of the Earth occurred by gravitational separation of the lightest elements into the atmosphere and the densest elements into the core.

 

Chemical Bonds

What is a molecule?
Molecule: group of bonded atoms; e.g., H2O, SiO2, NaCl

What is a mineral?
Mineral: a solid of specific composition with a regular arrangement of atoms

How do atoms bond together to form minerals?
Elements bond by sharing or transferring electrons

Why don't elements prefer to remain alone, unbonded?
Elements like to have their outer electron orbital full of electrons, so elements with full orbitals are very stable (e.g., the noble gases He, Ar, Kr, Xe)
elements near the left side of the periodic table (e.g., K+, Mg2+) like to give up electrons (the next lower orbital becomes full), while those near the right side like to gain electrons to become full (e.g., S2–, Cl–)

ionic bond: electrostatic attraction between cations and anions; charge balanced

 

 

covalent bond: sharing of electrons when orbitals overlap

 

metallic bond: special type of covalent bond in which electrons are freer to migrate around crystals 

 

hydrogen bond: weak electrostatic attraction among individual polar molecules (e.g., H2O)

hydrogen bonding in ice

van der Waals bond: weak electrostatic attraction between molecular sheets

geckos may climb using van der Waals forces

van der Waals forces hold sheets of C together

 

bond length: separation between atoms that are bonded

effective radius of an atom is its size within a crystal lattice

effective radius is affected by oxidation state, with cations smaller than the neutral atom and anions larger:

effective radius is affected by density of packing/coordination:

mineral formula

e.g., Ca2+Mg4+Si4+2O2—6

charge balance

 

Crystal Structure

Read Chapter 4 of Nesse

If Si and O are the most common elements in Earth’s crust, what are common minerals made of?
silicates are the most common minerals because O is the most common anion and Si is the most common cation

How do Si and O bond together to form 3-D structures?
Is SiO4 a stable compound?
SiO4 has a net negative charge of 4–; this must be balanced by cations

What structure can be formed from pure Si and O?
Quartz: SiO2 in a 3-D array of tetrahedra, each of which is joined to other tetrahedra at all 4 corners; quartz is 100% SiO2 and has a density of 2.65 g/cm3

the minimum coordination number for an element that is part of a 3D mineral is IV, thus SiO4, (cannot form 3-D structures from 3-coordinated things like CO3)

 

coordination number: number of atoms surrounding another

3-fold, III, planar only

 

4-fold IV tetrahedral

5-fold, V (L) trigonal bipyramid or (R) pentagonal bipyramid

6-fold VI octahedral

7-fold VII

8-fold VIII (see BCC below)

10-fold X

12-fold XII (see FCC and HCP below)

real example, diopside

VIIICa2+VIMg4+IVSi4+2O2—6

 

close packing

because metals share electrons freely, they can attain close packing

Here’s a helpful animation to see how cannonballs stack to make tetrahedra: http://upload.wikimedia.org/wikipedia/en/3/32/Animated-HCP-Lattice.gif

 

hexagonal closest packing 12 neighboring atoms

cubic closest packing (face-centered cubic packing) 12 neighboring atoms

 

body-centered cubic packing

8 neighboring atoms

based on a square, rather than triangular, plane lattice

 

 

 

Lattices, Symmetry, Point Groups, Space Groups

Read Chapter 2 of Nesse

plane lattice: a 2D pattern of atoms that extends infinitely

(from http://www.emat.ua.ac.be/Images/WebNovCerBulk.jpg)

 

space lattice: a 3D pattern of atoms that extends infinitely

crystal axes: vectors defined by the unit cell

unit cell: minimum portion of space lattice required to describe crystal (may be more than once choice)

 

There are six types of unit cell:

isometric

a = b= c

a = b = g = 90°

hexagonal

a ≠ c

a = 90° g = 60°

tetragonal

a = b ≠ c

a = b = g = 90°

orthorhombic

a ≠ b ≠ c

a = b = g = 90°

monoclinic

a ≠ b ≠ c

a = g = 90° ≠ b

triclinic

a ≠ b ≠ c

a ≠ b ≠ g

You may find the movies here helpful:

http://www.gly.uga.edu/schroeder/geol3010/3010lecture05.html

cubic example: garnet

 

cubic example: fluorite

tetragonal example: rutile

tetragonal example: zircon

 

hexagonal example: quartz

hexagonal example: calcite

 

(from www.mineralminers.com/.../mins/perm111.jpg)

orthorhombic example: olivine

 

(from http://www.telefonica.net/web2/barahonamicros/0100_Diopside_Jumilla_Murci.jpg)

monoclinic example: diopside

(from http://eps.berkeley.edu/~wenk/EPS100A/P5-2-Amazonite.jpg)

triclinic example: albite

 

see http://www.uwsp.edu/geo/projects/geoweb/participants/dutch/symmetry/unitcell.htm for some nice examples of how crystal forms are made up of unit cells

 

The distribution of atoms in the unit cell (P, primitive; F, face centered; I, body centered or Innenzentrierte) gives rise to the 14 Bravais lattices (above)

 

Crystal Faces

crystal faces tend to be close-packed planes of atoms

prism

set of faces parallel to one direction

rhombohedron

6 rhomb-shaped faces like a stretched or squashed cube

tetrahedron

4 triangular faces

 

If you like, for more crystal forms, see http://www.uwsp.edu/geo/projects/geoweb/participants/dutch/symmetry/xlforms.htm

octahedron

 

Point symmetry and Point Groups

Point symmetry operations in 2D are

 

reflection

like a mirror

 

rotation

around an axis

reflection and rotation produce the 10 2D point groups

Adding a 3rd dimension permits a 3rd symmetry operation:

rotoinversion: rotation + inversion

rotoinversion axes have a bar over the top of the number to distinguish them from ordinary rotation axes

note that rotoinversion is a simple center of symmetry like the room drawing below. The  rotoinversion is equivalent to a mirror plane

after Bloss (1971)

and leads to the 32 space groups, with their Hermann–Mauguin symbols (the first symbol of each stereonet below)

(from http://xrayweb.chem.ou.edu/images/ptgroups1.gif)

 

crystal system

1st symbol

2nd symbol

3rd symbol

cubic

4, 4/m, , 2, 2/m

3,

2, 2/m, m

hexagonal

6, 6/m, , 3,

2/m, m

2, 2/m, m

tetragonal

4, 4/m,

2, 2/m, m

2, 2/m, m

orthorhombic

2, 2/m, m

2, 2/m, m

2, 2/m, m

monoclinic

2, 2m, m

 

 

triclinic

1,

 

 

example: 6 2/m 2/m

 

Miller indices

are used to describe crystal faces and directions

Directions

Miller indices for directions are integers that describe the vector representation of the direction;

e.g., [104] is the direction that points 1 unit cell in the a direction and 4 unit cells in the c direction and is parallel to the b axis.

[uvw] describes a specific direction; <uvw> is a family of crystallographically equivalent directions

 

Planes

Miller indices for planes are integers that are the reciprocal of the intersection with each axis;

e.g., (104) is the plane that intersects the a axis at 1 unit-cell spacing and the c axis at 1/4 unit-cell spacing and is parallel to the b axis.

 

 (hkl) describes a specific plane; {hkl} is a family of crystallographically equivalent planes

somewhat more painful in the hexagonal system

[uvtw] describes a specific direction; <uvtw> is a family of crystallographically equivalent directions

t = – (u+v)

(hkil) describes a specific plane; {hkil} is a family of crystallographically equivalent planes

i = – (h+k)

 

Phase Transformations

Read Chapter 4 of Nesse

Isostructural transformation: same structure, different composition (e.g., carbonates, MCO3)

Polymorphism: same composition, different structure (e.g., C, SiO2)

reconstructive polymorphism: bonds must be broken and reformed (e.g., C, graphite, diamond)

 

(from http://www.prettyrock.com/php/mineraldetail.php?f=&n=Diamond)

graphite = hexagonal 6/m 2/m 2/m, H = 1–2, density = 2.1 g/cm3

diamond = cubic 4/m  2/m, H = 10, density = 3.5 g/cm3

 

(from http://www.emporia.edu/earthsci/amber/go336/salley/pics/carbon.gif) (from http://fixedreference.org/2006-Wikipedia-CD-Selection/images/65/6506.png)

 

graphite structure: click for animation

diamond structure: click for animation

 

(from http://www.eos.ubc.ca/research/diamonds/kopylova/pics/Maar_xsect1.gif) (from http://www.min.tu-clausthal.de/www/lager/Exc2005/bilder/klein/sa041_b.htm)

 

displacive polymorphism: bonds rotate, change length (e.g., a quartz, b quartz)

(from http://www.auburn.edu/~hameswe/Quartzpage.html)

See the following nice discussion of silica polymorphs: http://www.uwsp.edu/geo/projects/geoweb/participants/dutch/PETROLGY/Silica%20Poly.HTM

Here’s an animated gif of the a–b transition: http://www.rocksandminerals.org/suppl_nd06.php

 

See the following nice discussion of ice polymorphs: http://www.uwsp.edu/geo/projects/geoweb/participants/dutch/PETROLGY/Ice%20Structure.HTM 

 

Phase Transformation Textures and Rates

http://www.geol.ucsb.edu/faculty/hacker/geo102C/lectures/part10.html

 

Mineral Chemistry

Read Chapter 9 of Nesse

How mineral compositions are measured with an electron microprobe http://www.geol.ucsb.edu/faculty/hacker/geo102C/lectures/part9.html

 

How to calculate a mineral formula

Table 9.3; see p. 173

 

Mineral Growth

Read Chapter 5 of Nesse

solid solutions

mineral

end members

exchange vector

olivine

forsterite Mg2SiO4 <—> fayalite Fe2SiO4

Fe2+ <—> Mg2+

plagioclase

albite NaAlSi3O8 <—> anorthite CaAl2Si2O8

Na+ Si4+ <—> Ca2+ Al3+

amphibole

tremolite Ca2Mg5Si8O22(OH)2 <—> tschermakite Ca2(Mg3Al2)(Al2Si6)O22(OH)2

VIMg2+ IVSi4+ <—>VIAl3+ IVAl3+ (tschermak exchange)

mica

muscovite KAl2(AlSi3)O10(OH)2 <—> phengite KMgAlSi4O10(OH)2

VIAl3+ IVAl3+ <—> VIMg2+ IVSi4+(inverse tschermak exchange)

 

Mineral growth, diffusion, zoning

Diffusion is the transfer of mass via the motion of individual atoms or molecules.
Diffusion within crystals is often discussed in terms of point defects, which are missing atoms (vacancies) or extra atoms in the crystal lattice. Every crystal has an equilibrium number of vacancies that allows the crystal to be in a lower free energy state than if it were perfect crystal-this is important because it means that crystals are always "ready to go" when it comes to diffusion.

(from http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/met_minerals.htm#Al-silicates)

Crystal Structures

Read Chapter 20, Chapters 11–19 of Nesse

 

Oxides

Ice H2O hexagonal

(see phase diagram that we looked at earlier in class)

 

Hydroxides

‘bauxite’

Al hydroxide

Al foil

MnO·OH

Mn hydroxide

pigment

bauxite

 

XO2 group

tetrahedral

rutile

TiO2

source of Ti

uraninite

UO2

source of U

(from http://www.hgs-model.com/gallery/img/photo_Rutile02.gif)

rutile structure

rutile                                                   uraninite

 

X2O3 group

cubic

hematite

Fe3+2O3

 

corundum

Al3+2O3

source of Cr (ruby)

ilmenite

Fe2+Ti4+O3

source of Fe

hematite                                                        corundum                  ilmenite

hematite structure

crystal structure movie: http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/hem.mov

 

Spinel

XY2O4 cubic

spinel

MgAl2O4

 

chromite

FeCr2O4

source of Cr

magnetite

Fe2+Fe3+2O4

source of Fe

 

   

spinel                                                  chromite                                magnetite

(from http://www.tf.uni-kiel.de/matwis/amat/def_en/kap_2/illustr/spinel.gif)

 

Carbonate Minerals

calcite

CaCO3

hexagonal

2.71 g/cm3

aragonite

CaCO3

orthorhombic

2.94 g/cm3

magnesite

MgCO3

 

 

dolomite

CaMg(CO3)2

 

 

calcite structure

      

Sulfate Minerals

gypsum

hydrous CaSO4

evaporites

wallboard

anhydrite

CaSO4

evaporites

 

barite

BaSO4

Ba source

dense additive

 

alabaster                                            anhydrite

 

barite structure

 

Phosphate Minerals

apatite hydrous calcium phosphate

Tungstate Minerals

scheelite CaWO4

(from http://www.wrightsrockshop.com/gallery/wulfenitemimetite/wulfenitemimetitemiscellaimages/scheelite022504.JPG)

source of W

Pine Creek Mine near Bishop

 

Borate Minerals

borax hydrous Na borate

source of B

 

Halide Minerals

halite

NaCl

cubic

fluorite

CaF2

cubic

halite; Na+ (green) coordinated with six Cl– (orange)

fluorite; Ca2+ (grey) coordinated with eight F– (yellow)

 

Sulfide Minerals

sphalerite

ZnS

cubic

galena

PbS

cubic

pyrite

FeS

cubic

molybdenite

MoS2

hexagonal

   

sphalerite                               galena                                     pyrite

pyrite; (Fe2+ yellow, S2– gray)

 

Silicate Minerals

 

 

no of O shared per tetrahedron

orthosilicates

nesosilicates

0

disilicates

sorosilicates

1

ring silicates

cyclosilicates

2

chain silicates

inosilicates

2 or 3

sheet silicates

phyllosilicates

3

framework silicates

tectosilicates

4

nesosilicate (from http://classes.colgate.edu/rapril/geol201/summaries/silicates/neso.htm)

sorosilicate (from http://classes.colgate.edu/rapril/geol201/summaries/silicates/soro.htm)

cyclosilicate (from http://classes.colgate.edu/rapril/geol201/summaries/silicates/cyclo.htm)

single-chain inosilicate (from http://classes.colgate.edu/rapril/geol201/summaries/silicates/ino.htm)

double-chain inosilicate (from http://classes.colgate.edu/rapril/geol201/summaries/silicates/amphib.htm)

phyllosilicate (from http://classes.colgate.edu/rapril/geol201/summaries/silicates/phyllo.htm)

tectosilicate (from http://classes.colgate.edu/rapril/geol201/summaries/silicates/tecto.htm)

 

Framework Silicates (Tectosilicates)

Quartz etc.

SiO2 vs SiO4

 

SiO2 phase diagram: http://darkwing.uoregon.edu/~cashman/GEO311/311pages/L5_crystallization_files/image001.gif

 

ab plane of beta quartz, showing heights of SiO2 tetrahedra arranged in hexagonal array to form framework in which each tetrahedron shares four corners (after Putnis, 1992)

 

a quartz b quartz, showing positions of Si atoms(after Putnis, 1992)

Feldspar

monoclinic and triclinic

   (from http://csmres.jmu.edu/geollab/Fichter/IgnRx/ssblnk.gif)

K-feldspar KAlSi3O8

crystal structure movie:http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/Sanidine.mov (SiO4 and AlO4 tetrahedra blue, K 9-fold sites red)

sanidine     

monoclinic

high T, rapid cooling

complete Al/Si disorder

orthoclase

monoclinic

moderate T, cooling

partial Al/Si order

microcline

triclinic

low T, slow cooling

complete Al/Si order

(from http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/met_minerals.htm#Al-silicates)

(from http://www.geo.auth.gr/212/6_tekto/fds_perthite/perthite_06x.jpg )

perthite: albite exsolution lamellae in K-feldspar host

(from http://www.tulane.edu/~sanelson/images/solv_subsolv.gif )

plagioclase NaAlSi3O8–CaAl2Si2O8

amazonite (albite)

high albite 

triclinic

high T, rapid cooling

complete Al/Si disorder

intermediate albite

triclinic

moderate T, cooling

partial Al/Si order

low albite

triclinic

low T, slow cooling

complete Al/Si order

 

crystal structure movie: http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/Albitem.mov (SiO4 and AlO4 tetrahedra blue, Na 9-fold sites red)

http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/Anorthite.mov  (SiO4 tetrahedra blue, AlO4 tetrahedra grey, Ca 9-fold sites red)

albite–anorthite

albite–An10–oligoclase–An30–andesine–An50–labradorite–An70–bytownite–An90–anorthite

(from http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/met_minerals.htm#Al-silicates)

feldspar twinning

     

(from http://www.geo.auth.gr/212/6_tekto/fds_twin.htm)

Carlsbad [001](010)            Albite ┴(010)(010)   Pericline [010](h0l) Albite and Pericline

 

Zeolites

 ‘(Na, K)(Ca, Mg)(AlSiO)’·mH2O

important filtering agents

crystal structure movie: http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/Analcime.mov (SiO4 tetrahedra blue, AlO4 tetrahedra purple, Na pink, H2O yellow)

analcime NaAlSi2O6•H2O

laumontite CaAl2Si4O12•4H2O

 

Orthosilicates (Nesosilicates)

SiO4 + cations

olivine

(from http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/met_minerals.htm#Al-silicates)

orthorhombic

forsterite Mg2SiO4

in ultramafic rocks

fayalite Fe2SiO4

crystal structure movie: http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/olivine.mov (SiO4 tetrahedra blue, Fe & Mg distorted octahedral sites yellow, Fe & Mg octahedral sites orange)

(from http://www.tulane.edu/~sanelson/images/olivinephasediag.gif )

 

Garnet X3Y2Si3O12

almandine Fe

pyrope Mg

grossular Ca

spesssartine Mn

laser Y3Al2Si3O12

(from http://www.geo.uni-potsdam.de/Mitarbeiter/OBrien/obrien/Atoll/index.html)

crystal structure movie: http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/garnet.mov (SiO4 tetrahedra blue, Al octahedra red, M2+ distorted 8-fold sites cyan)

 

Aluminumsilicates

Al2SiO5

sillimanite VIAlIVAl

orthorhombic

high temperature

andalusite VIAlVAl

orthorhombic

low pressure

kyanite VIAlVIAl

triclinic

high pressure

     

andalusite                        sillimanite                                          kyanite (after Putnis, 1992)

 

crystal structure movies:

http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/andalusite.mov (SiO4 tetrahedra blue, VIAl pale blue, VAl green)

http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/sillimanite.mov (SiO4 tetrahedra blue, VIAl pale blue, IVAl yellow)

kyanite (from http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/met_minerals.htm#Al-silicates)

sillimanite (fibrolite) (from http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/met_minerals.htm#Al-silicates)

 

zircon

ZrSiO4

(from http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/met_minerals.htm#Al-silicates)

crystal structure movie: http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/zircon.mov (SiO4 tetrahedra blue, Zr4+ 8-fold sites green)

 

sphene

CaTiSiO4(OH,Cl,F)4

 

staurolite

(Mg,Fe)2Al9Si4O22(OH)2

 

(from http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/met_minerals.htm#Al-silicates)

 

Disilicates (Sorosilicates)

paired SiO4 tetrahedra, Si2O7

epidote hydrous Ca-Al silicate

Ca2(Al,Fe+3)Al2Si3O12(OH)

monoclinic

has 7 and 11-fold coordinated sites

crystal structure movie: http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/epidote.mov (Ca 7- and 11-fold sites green, Si tetrahedra chains blue, Al M2 octahedral site cyan, Al–Fe M1 octahedral site yellow)

(from http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/met_minerals.htm#Al-silicates)

 

zoisite hydrous Ca-Al silicate

orthorhombic

Ca2Al3Si3O12(OH)

 

lawsonite hydrous Ca-Al silicate

indicates high pressure

 

Ring Silicates (Cyclosilicates)

beryl Be silicate

Be3Al2Si6O18

emerald Cr-beryl

(SiO4 tetrahedra yellow, Al 6-fold sites gray, Be 4-fold sites green)

 crystal structure movie: http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/beryl.mov (SiO4 tetrahedra blue, Al 6-fold sites green, Be 4-fold sites pale green; ignore the yellow and pink)

 

tourmaline Li–B silicate

Na(Mg,Fe,Mn,Li,Al)3Al6Si6O18(BO3)3(OH)4

crystal structure movie: http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/tourmaline.mov (SiO4 tetrahedra cyan, Na+ or OH– yellow, Al cyan, Li & Mg and Al purple, BO3 pale green)

(from http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/met_minerals.htm#Al-silicates)

 

Chain Silicates (Inosilicates)

Pyroxene

 

crystal structure movies:

orthopyroxene, showing tetrahedral chains: http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/diopibeam.mov (SiO4 tetrahedra blue, Mg & Ca octahedra yellow)

http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/opx.mov  (SiO4 tetrahedra blue, Mg & Ca octahedra yellow)

http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/diopside.mov  (SiO4 tetrahedra blue, Mg octahedra yellow, Ca octahedra orange)

 

orthorhombic and monoclinic

VIII or VIXVIYIVZ2O6

VIII or VIM2VIM1IVT2O6

(from http://www.tulane.edu/~sanelson/eens212/olivines&pyroxenes.htm) (from http://www.nature.com/nature/journal/v406/n6791/fig_tab/406059a0_F2.html )

enstatite

MgSiO3

ferrosilite

FeSiO3

wollastonite

CaSiO3 common in skarns

diopside

CaMgSi2O6

hedenbergite

CaFeMgSi2O6

jadeite

NaAlSi2O6 indicates high pressure

(from http://www.tulane.edu/~sanelson/eens212/olivines&pyroxenes.htm)

augite (Na,Ca,Fe,Mg)(Al,Ti,Si)2O6

 

Amphibole

orthorhombic and monoclinic

XW0–1VIII or VIX2VIY5IVZ8O22(OH)2

XA0–1VIII or VIM42VI(M1, M2, M3)5IVT8O22(OH)2

 

 crystal structure movies:

http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/tremolite.mov (SiO4 tetrahedra blue, Mg octahedra yellow, Ca 8- or 6-fold sites pale blue, Na 10-fold site green)

http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/glaucophane.mov  (SiO4 tetrahedra blue, Mg octahedra yellow, Al 8- or 6-fold sites pale blue, Na 10-fold site green)

anthophyllite []Mg2Mg5Si8O22(OH)2

Mg–Fe orthoamphibole

Mg–Fe rich rocks: ultramafic

tremolite–actinolite []Ca2Mg5Si8O22(OH)2

Ca–Mg–Fe clinoamphibole

tremolite is Mg endmember; actinolite is Fe endmember

blackwall rinds

glaucophane []Na2(Mg3Al2)Si8O22(OH)2

Na clinoamphibole

indicates high pressure

(from http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/met_minerals.htm#Al-silicates)

 

hornblende (Na, K)Ca2(Mg, Fe2+, Fe3+, Al, Ti) 5Si8O22(OH)2

K, Na, K, Mg, Fe, Al clinoamphibole

(from http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/met_minerals.htm#Al-silicates)

 

Sheet Silicates (Phyllosilicates)

made of interlayered octahedral (two planes of OH– with interlayer 2+ or 3+ cations) and tetrahedral sheets

(from http://classes.colgate.edu/rapril/geol201/summaries/silicates/phyllo.htm)

brucite: Mg(OH)2 single di-octahedral sheet

di-octahedral sheet contains 3+ cations; the 6– charge of the anions is satisfied by two 3+ cations, so two or every three sites is vacant; each O or OH is bonded to two cations

 (after Nesse, 2000)

gibbsite: Al(OH)3 single tri-octahedral sheet

tri-octahedral sheet contains 2+ cations; the 6– charge of the anions is satisfied by three 2+ cations, so no sites are vacant; each O or OH is bonded to three cations

(after Nesse, 2000)

serpentine: Mg3Si2O5(OH)2

TO structure  (from http://classes.colgate.edu/rapril/geol201/summaries/silicates/phyllo.htm)

lizardite, chrysotile, antigorite

lizardite crystals are small because of mismatch between octahedral and tetrahedral layers

asbestos, including crocidolite amphibole

 (after Nesse, 2000)

talc: Mg3Si4O10(OH)2

(from http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/met_minerals.htm#Al-silicates)

TOT structure  (from http://classes.colgate.edu/rapril/geol201/summaries/silicates/phyllo.htm)

crystal structure movie: http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/talc.mov

 

muscovite: KAl2(AlSi3O10)(OH)2

(from http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/met_minerals.htm#Al-silicates)

TOT + interlayer cation

(after Nesse, 2000)

crystal structure movie: http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/muscovite.mov

 

biotite: K(Mg, Fe)3(AlSi3O10)(OH)2

phlogopite is Mg endmember; found in mantle

TOT + interlayer cation like muscovite

F13.3

crystal structure movie:http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/phlogopite.mov

 

chlorite: (Mg, Fe)3(Al, Si)4O10(OH)2

crystal structure movie: http://ist-socrates.berkeley.edu/~eps2/wisc/geo360/chlorite.mov

TOT + interlayer cation = talc + brucite

(after Nesse, 2000)

(from http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/met_minerals.htm#Al-silicates)

 

clay minerals

kaolinite

smectite

illite

drilling mud, ceramics, cosmetics, absorbents, food

(after Nesse, 2000)