1. Composition of the Earth’s Crust
Our planet’s crust is mostly silica.

2. Silica Tetrahedron

3. Silica Tetrahedral Framework
3-D framework
Each silica tetrahedron is joined to its 4 nearest neighbours by sharing the oxygens at the vertices of the tetrahedra. Each oxygen is bonded to two silicons, and each silicon is bonded to 4 oxygens.
The overall ratio is: SiO2
The molecule extends out in all directions. Each crystal is a single marcomolecule.

4. Tectosilicates: Framework Silicates
Silica SiO2

5. Alpha
Beta
Quartz
(12%)

6. 2D view of the 3D framework in silica glass.
(modern glass has other components in it)

7. Feldspars
Silica framework molecules in which a set ratio of silicon atoms are substituted with aluminum atoms.
Since aluminum has one fewer electrons than silicon, an additional metal atom must be squeezed into the gaps between the tetrahedra to provide the additional electron.
The mineral still forms a macromolecular lattice, just slightly more complex. The distortion in the lattice structure caused by the other metal ions produces the cleavage planes of weakness.

8. Orthoclase Feldspar (12%)
KAlSi3O8
1 aluminum tetrahedron for each 3 silica tetrahedra: So, could be written as: K(AlO2)(SiO2)3

10. Plagioclase Feldspars (39%)
Solid Solution from:
NaAlSi3O8 to CaAl2Si2O8
Also could be: Na(AlO2)(SiO2)3 and
Ca(AlO2)2(SiO2)2

11. Phyllosilicates: Sheet Silicate micas (5%) and clay minerals (5%)
Kaolinite
Muscovite

13. Inosilicates: Single Chain Silicates
Pyroxenes (11%)
There are two tetrahedra in the unit cell. Two oxygens are shared outside of the cell and 1 is shared within. Thus, there are 4 oxygens not shared, so the charge is 4-.

14. Inosilicates: Double Chain Silicates
Amphiboles (5%)
There are 4 tetrahedra in the unit cell. 4 oxygens are shared with other cells and 3 are shared within the cell. This leaves 6 unshared oxygens, thus the 6- charge.

15. Nesosilicates: Island Silicates Isolated Silica Tetrahedra
Olivines (<3%)

16. Garnet
X3Y2(SiO4)3
X = 2+ ions: Ca, Mg, Fe, Mn
Y = 3+ ions: Al, Fe, Cr

17. Non-Silicate Mineral Groups
(<8% of the crust in total)
Carbonates
Sulfates
Halides
Oxides
Phosphates
Sulfides
Hydroxides
Elements

18. Carbonates Flat, rather than tetrahedral.
Forms ionic substances rather than polymerizing to make macromolecules.
Can be produced by both inorganic and organic processes.

19. Calcium Carbonate

20. Calcite

21. Dolomite
MgCa(CO3)2
Distinguished from calcite and aragonite by visibly reacting with 10% HCl only when powdered.

22. Siderite
FeCO3
Rhodochrosite
MnCO3
Azurite
Cu3(CO3)2(OH)2
Malachite
Cu2CO3(OH)2

23. Usually the first mineral to start precipitating when sea water evaporates.

24. Halides
Halite
NaCl
Fluorite
CaF2

25. <-- hematite with powdery surface
Oxides
Hematite Magnetite
Fe2O Fe3O4
(FeO + Fe2O3)
Corundum
Al2O3
Includes sapphire and ruby
<-- hematite with powdery surface

26. Phosphates
Apatite
Ca10(PO4)6(OH,F,Cl)2
Sulfides
Pyrite
FeS2
Galena
PbS

27. Hydroxides
Gibbsite
Al(OH)3