Download ch-8 [Rocks and minerals]

Minerals and Rocks
Chapter 8
phsc001, chapter 8, yuc
1
Earth’s Crust Materials
Crust: upper part of earth
• 8 light elements and their
compounds make up 89%
of crust
- silicon and oxygen are
most abundant
• Initially earth was molten
- heavy elements sank
- light elements stay on top
phsc001, chapter 8, yuc
2
Minerals
Minerals
• Naturally found
• Solid element or
compound
• Crystal structure
- ordered repetition of
unit cell (structural
unit)
- unit cell contain one
element or more
• Example: table salt
crystal
phsc001, chapter 8, yuc
3
Crystal Form
• Each mineral has unique
crystal shape
• Minerals can be identified by
their crystal structures
• No two minerals can have
same crystal structure
• Graphite and diamond both
have carbon but different
crystal structures
diamond
graphite
phsc001, chapter 8, yuc
4
Quartz crystal structure
Quartz: SiO2
phsc001, chapter 8, yuc
5
Gold Crystal Structure
phsc001, chapter 8, yuc
6
Topaz Crystal Structure
• Topaz: Al2SiO4(F,OH)2
Aluminum silicate fluoride
hydroxide
phsc001, chapter 8, yuc
7
Mineral Physical Properties
• Crystal form
• Hardness : measure of
resistance to scratching
- Moh’s hardness scale: 1
(weak), 10 (hard)
Example: Talc (1), feldspar
(6), Diamond (10)
• Cleavage: break a long
planes of weakness into
regular shapes
• Fracture: break along
curved surfaces with irregular
shapes. Minerals that fracture
do not have planes of
weakness
phsc001, chapter 8, yuc
Cleaved mineral
Fractured minerals
8
(
Mineral Physical Properties Cont
• Color : not reliable
- minerals found in many
colors
- chemical impurity give
special colors. Corundum (Al 2 O3 )
changes into sapphire, rubies
sapphire
• Density: mass/volume a
measure how massive a
mineral
- silver : 10.5 g/cm3
- gold : 19.3 g/cm3
Ruby
phsc001, chapter 8, yuc
9
Minerals Classification
phsc001, chapter 8, yuc
10
Silicates
• Contain Mostly silicon and
oxygen
• Make up 92% of Earth’s crust
• Two divisions
Ferromagnesian silicates
•
•
•
Ions of iron, magnesium
Darker color, high density,
Example: Biotite, augite, hornblend,
Olivine
Nonferromagnesian silicates
•
•
Lighter color, lower density
Example: muscovite, feldspars,
quartz
phsc001, chapter 8, yuc
11
Nonsilicates
• Contain no silicon-oxygen
in crystalline structure
• Make up remaining 8% of
Earth’s crust
• Eight groups of
nonsilicates
1. Carbonates (most found)
2. Sulfates
3. Oxides
4. Sulfides
5. Halides
6. Phosphates
7. Hydroxides
8. Native elements
sulfide
Halides (CaF2)
phsc001, chapter 8, yuc
12
Rocks
• Physical combination of
one or more minerals
• Most are silicates
• Classification: Based on
how the rock formed
- Igneous
- Sedimentary
- metamorphic
metamorphic
phsc001, chapter 8, yuc
13
Igneous Rocks
• Formed from magma above
or below Earth’s surface.
Three stages
- High temperature to melt rock
- Formation of magma
- Cooling and recrystalization of
magma
Examples
• Granite
- Light colored, less dense
- Made up of quartz, mica, feldspar
• Basalt
- dark colored, high dense
phsc001, chapter 8, yuc
14
Sedimentary Rocks
• Formed from dissolved
materials from previously
existing rocks due to
Weathering and erosion
caused by rain, snow, wind
sandstone
shale
• Sediments
– Accumulations of silt,
sand or other materials
that settled out of water
In lakes, rivers, or oceans
Examples: sandstone,
shale, coal, limestone
Limestone
coal
phsc001, chapter 8, yuc
15
Sedimentary rocks
phsc001, chapter 8, yuc
16
Metamorphic Rocks
• Previously existing rocks
(igneous or sedimentary)
changed by heat, pressure
into different rock
•
•
Sources of heat, pressure
– Movement of the crust
(earthquake)
– Heating from magma
– Temperatures must be
high enough to cause
recrystallization, but not
melting
Example: slate, schist, gneiss
phsc001, chapter 8, yuc
17
Rocks Cycle
• Rocks transformed from
one form to another due
environmental conditions
like rain, wind, snow, which
result in weathering and
erosion of rocks. Also, by
changes in earth’s interior
phsc001, chapter 8, yuc
18