Download Lecture 1 Intro to Geology and Minerals

Physical
Geology
Intro to Geology
What is Geology?
 Greek
 Geo
Origin:
– meaning “Earth”
 -logy – meaning “the
study of”
 Like Biology (Study of
life), Psychology
(Study of the Mind)
 Geology is the study of
the Earth
Unifying Themes in Geology
 Plate

Tectonics
Lithosphere is divided into plates, which move
because of convection cells in asthenosphere
Unifying Themes in Geology
 Rock

Cycle
The
transformation
of one type of
rock to another
(recycling of
Earth material)
Unifying Themes in Geology
 Geologic


Time
Earth’s history is
reconstructed
through absolute
and relative dating
Uniformitarianism
“Truths” for the Earth Sciences
 The
Earth is dynamic
 The
Earth is very old
 Life
has evolved on Earth
 Humans
exist in a perilous geologic environment
Physical
Geology
Minerals
What is a Mineral?
A
naturally occurring,
inorganic crystalline
solid, with definite
chemical composition
and physical properties
 Minerals can be used in
construction, for
gemstones and also
sources of chemical
elements
Chemistry of Geology
 Of
the 92 naturally occurring chemical
elements, most of the Earth's crust is made
of only 8 elements



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
O (oxygen)
46.6
Si (silicon)
27.7
Al (aluminum)
8.1
Fe (iron)
5.0
Ca (calcium)
3.6
Na (sodium)
2.8
K (potassium)
2.6
Mg (magnesium) 2.1
all others
1.5
Mineral Groups
Minerals are classified into classes (groups)
based on chemical composition
 Halides
 Sulfides
 Carbonates
 Oxides
 Phosphates
 Sulfates
 Silicates
 Native
Elements
Nature of Minerals
 Crystalline
solids, regular
3D framework

Amorphous -> without
form
 Not
a mineral (Example:
Obsidian)
 Over
3,500 different
minerals, but only a few
are common
Nature of Minerals
 Substitution
 Many
minerals have a
constant chemical
composition
 Ex.
 In
Quartz -> SiO2
other minerals there is a
range of composition
because similar size ions may
substitute
 Ex.
Olivine -> Mg2SiO4 or Fe2SiO4
 Olivine is written (Mg,Fe)2SiO4
because Mg and Fe can be
interchanged/substituted.
Identifying Minerals
 Color
is NOT a reliable property!
Identifying Minerals
 Streak
(color of powdered sample – more
reliable)
 Luster (light reflected)

Metallic or nonmetallic
 Nonmetallic
earthy, etc.
 Crystal

can be glassy, vitreous, greasy,
form (crystals are rare!)
Minerals develop flat faces, sharp corners
and straight edges
Identifying Minerals
 Cleavage
(breaking or splitting along a
smooth plane of weakness)
 Fracture – breaking along irregular
surfaces

Uneven, conchodial (quartz)
Identifying Minerals
 Hardness

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1
2
3
4
(Moh’s Scale)
Talc
Gypsum
Calcite
Fluorite
5 Apatite (teeth are comprised of this mineral)
6 Orthoclase/Plagioclase Feldspar
7 Quartz
8 Topaz
9 Corundum (Ruby & Sapphire)
10 Diamond
Identifying Minerals
 Specific

Gravity
Density of
mineral
compared to
the density of
H2 O
Identifying Minerals
 Special
 Reacts
Properties
with acid
(effervesces)  Calcite
 Taste  Halite
 Feel  Graphite/Talc
 Magnetic  Magnetite
 Double refraction  Calcite
Earth Science Extra Credit
5
pts added to a test for a trilobite fossil for
me to keep
 15 pts added to a test for a starfish fossil
for me to keep
 35 pts added to a test for a eurypterid
fossil for me to keep