16. Types of Bonding
2) Covalent Bonding
- outer orbital shells overlap
- atoms share valence electrons
Ex: Oxygen gas (O2)
17. Atomic Bonding
3) Metallic bonding
- valence electrons move freely
between ions
- accounts for high electrical
conductivity
18. Structure of Minerals
2) Element – composed entirely of
same kind of atoms
- all atoms have same number of
___________
92 naturally occurring elements
22. Chemical Composition of Crust
98.3% of crust composed of 8
elements (Figure 2.19)
Other 84 elements share 1.7% of
remaining crust
- includes gold, zinc, lead, carbon,
sulfur, silver, …
23. Mineral Groups
1) Silicate Group - 90% of all
minerals
Basic building block is the silica
tetrahedron SiO44-
(Si = silicon; Si+O = silica)
28. Silicate Mineral Structures
Silicate minerals have unique
silica tetrahedra structures (Fig.
2.21)
- each structure is related to its
cleavage patterns (or fracture)
29. Silicate Mineral Structures
Bonds between silica tetrahedra
are strong
Bonds between tetrahedra and
positive ions are weak
Cleavage occurs between
tetrahedra and positive ions
30. Types of Silicate Structures (Fig.
2.23)
Mineral Structure
Olivine Isolated framework
(Mg,Fe)2SiO4 No shared oxygens
Si:O = 1:4
No cleavage b/c (+) ions not in
alignment
31. Types of Silicate Structures
Mineral Structure
Augite Single chain
(Mg,Fe)SiO3 One oxygen is
Si:O = 1:3 shared
32. Types of Silicate Structures
Mineral Structure
Hornblende Double Chain
Two oxygens are
shared
33. Types of Silicate Structures
Mineral Structure
Biotite & Sheet silicates
Muscovite
(+) ions link sheets of tetrahedra
together
Creates one plane of cleavage
34. Types of Silicate Structures
Mineral Structure
Quartz 3-D framework
SiO2 structure
1:2
All oxygen atoms are shared (no
cleavage)
35. “Silica rich” vs. “silica poor”
Based on Si:0 ratio
- as more oxygen atoms are
shared, the percentage of silicon
in structure increases
(compared to oxygen)
