B.Formation of Minerals:
By the process of crystallization, which could be initiated by three different pathways:
b.Reducing the amount of solvent in a solution
c.Diffusion of ion/atom in solid (usually at temperature > 250 C)
D. Physical Properties of Minerals
a.Crystal Form: external expression of internal structure
Left: pyrite- cubic crystal
right: Quartz- hexagonal crystal
b.Luster: the way the surface of a mineral reflects lights:
non-metallic: vitreous (glassy), pearly, earthy.
c.Color & streak
Colors of a mineral are variable
Streak: color of the fine mineral dust left on an abrasive surface
d.Hardness: Resistance to abrasion
Mohr scale of hardness (Figure 2.13)
Sheet silicates: 1-3
most other silicates:5-7
Carbonate & sulfate: <5
Physical Properties of Minerals – Cont.
e.Cleavage: the tendency of a crystal to break along flat planar surface, i.e. plane of weakness
Described by the number and orientation (angles between adjacent planes)
Related to crystal structure
Fig. 2.14: mica
fluorite, halite, calcite
f.Specific gravity & density
g.Fracture: the feature of a broken surface of a mineral without cleavage.
Fig. 2.16. Conchoidal fracture
h.Other properties: magnetism, taste, smell, reaction to acid, etc.
Over 4000 minerals; ~30 make up the bulk of crustal rocks.
Fig. 2.19: Relative abundance of elements in the continental crust
8 elements make up over 80% of the continental crust
Fig. 2.22: Relative size and charges of ions
D.Classification of Minerals
Silicate Minerals: comprise most of the rock-forming minerals
Fig. 2.20. The basic unit SiO4-4, a tetrahedron
Figure 2.23: Common silicate minerals
Non-silicate Mineral Groups: Table 2.1
E.What is Asbestos?
a.Not a single mineral
b.Silicate minerals readily separate into strong fibers
c.Flexible, heat resistance, inert
d.Three major asbestos:
Chrysotile: a serpentine (white asbestos)
Crocidolite (blue asbestos)
Amosite: an amphibole (brown asbestos)