Historical Geology 102
Minerals and Rocks


What is a Mineral?

Mineral Physical Properties
Physical aspects of a mineral, based on chemical composition and crystalline structure.

Physical Properties

Crystal Form
Other - Specific Gravity, Magnetism, Taste, Hydrochloric acid - HCl, Radioactivity, Fluorescence

Important Crustal Minerals

Feldspar Group (Plagioclase and Orthoclase)
Calcite and Dolomite
Pyroxene Group (Augite)
Amphibole Group (Hornblende)
Mica Group (Biotite and Muscovite)
Halite - "Salt"

Additional information and images on Igneous Rocks can be found at: Minerals

The Rock Cycle

Rock Cycle

Igneous Rocks

Rocks that formed from the cooling and crystallization of magma
Igni- =
-ous =
Origin of Magma
Magma - liquid rock or molten rock
Things needed to make magma:
Material to be melted - any pre-existing rock (crustal material) - mantle material


Increased temperature will cause melting
Sources of heat in the Earth's interior
Other magma
Thermal gradient - temperature increase with depth - ~30°C per kilometer

Partial Melting

Different materials melt a different temperatures
Partial melting is the melting of some of the material in a rock but not the entire rock.
The composition of a magma will be different from the composition of the rock if the rock is not completely melted


Reversal of melting resulting from:
Decrease in temperature (cooling)
Partial melting says that different material melt at different temperatures
Different materials solidify or crystallize at different temperatures

Additional information and images on Igneous Rocks can be found at: Igneous Rocks
Additional information and images on Volcanic Rocks can be found at: Volcanic Rocks
Additional information and images on Volcanoes can be found at: Volcanoes

Sedimentary Rocks

Rocks formed from:
Sediment - fragments of pre-existing rocks or minerals, biologic organisms or chemical precipitates

Additional information and images can be found at: Sedimentary Rocks

The Sedimentary Cycle

Sedimentary Cycle

Metamorphic Rocks

Meta- =
Morph =
Metamorphic rocks are rocks which have undergone a change of form.
Parent Rock is the original, unaltered, unchanged rock.
Parent rocks can be igneous, sedimentary or metamorphic rocks.
Metamorphism occurs due to changes in temperature, pressure or chemistry.

Temperature and Metamorphism

Changes in temperature will result in changes to the minerals or structure of the rock.
The temperature of metamorphism has two limits:
Lower limit of metamorphism - 200°C
Upper limit varies between 700-1200°C
What is the ultimate temperature of metamorphism?

Pressure and Metamorphism

Changes in pressure will change the crystalline structure of minerals and the structure of the rock.

Chemical Metamorphism

Hydrothermal fluid is hot water, plus other chemicals and gases.
1) remove chemicals from the rock
2) add chemicals to a rock
A change in chemistry will result in new minerals.
Change the minerals and the rock also changes.

Types of Metamorphism

Contact Metamorphism
Regional Metamorphism
Cataclastic Metamorphism
Burial Metamorphism
Shock Metamorphism

Additional information and images about Metamorphic Rocks can be found at: Metamorphic Rocks