Rocks

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Rocks
Minerals
Elements
Atoms
Protons, Neutrons, Electrons
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electrons
protons
nucleus
neutrons
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Relative sizes of ions of the common crustal
elements
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Compounds are formed by Chemical Bonding between
atoms

• Types of bonding include
• ionic
• covalent
• metallic
• van der Waals

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Covalent bonding - sharing electrons between two
ions
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What is a mineral?

• A chemical compound that is
• naturally occurring
• inorganic
• solid
• has fixed chemical composition
• and regular crystalline structure

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QUARTZ
CONSTANCY OF INTERFACIAL ANGLES
The angles between equivalent faces of crystals
of the same substance, measured at the same
temperature, are constant.
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CALCITE
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Physical Properties of Minerals

• crystal form luster
• color taste
• hardness reaction to acid
• density magnetism
• fracture, cleavage

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Minerals are classified according to their
chemistry.

• silicates (SiO4)
• carbonates (CO3)
• sulfates (SO4)
• sulfides (S)
• oxides (O)
• halides (Cl, F, Br)
• native elements (Au, Ag, Cu)

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Silicate minerals are also classified according
to their crystal structure.

• The commonest minerals of the crust and mantle
  are silicates
• Silicates have the (SiO4)-4 anionic group as the
  fundamental unit of the structure
• (SiO4)-4 groups are combined with other (SiO4)-4
  groups and with cations to form the different
  silicate minerals.

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THE SILICATE TETRAHEDRON -
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Other representations of the silicate tetrahedron
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Covalent bonding holds together the silicate
anionic group.
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A single SiO4 tetrahedron with no shared oxygens.
Single chain of SiO4 tetrahedra.
Double chain of SiO4 tetrahedra.
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Two dimensional sheet of SiO4 tetrahedra form
when each SiO4 unit shares three of its oxygens
with adjacent tetrahedra.
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What governs the kind of minerals that form?

• temperature
• pressure
• chemistry of the environment in which the mineral
  forms

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How are minerals formed in nature?

• From a water solution. The chemicals in the
  solution come from dissolving other minerals.
• From a silicate melt. The melt comes from melting
  minerals.
• By heating and compressing minerals, rearrange
  the ions of the old structure and make a new one.