Download How do minerals form?

How do minerals form?
Notes: 3/13/09
How do mineral crystals form?
A. Rivers carrying sediment deposits it
B.
C.
D.
E.
somewhere
Water evaporates leaving behind
minerals that were dissolved
Molten rock cools and crystallizes.
All of the above
B and C only
Crystallization of Melted
Minerals
 The closer to the surface, the faster the
magma cools


Slow cooling (1000s of years)
Fast cooling (The minerals get hard before the
atoms have time to get into crystal shapes)
Crystallization of
Minerals Dissolved in
Water
 Hot water solutions in
the earth cool and
minerals form

Example: metals found
in veins
 Evaporating water can
leave behind crystals

Example: sea water
leaving potassium
crystals
Types of Minerals
 Silicates
 Contain a mixture of
oxygen and silicon
 make up 75-90% of
earth’s crust
 Nonsilicates
 NOT formed from
oxygen and silicon
 Combinations of
oxygen, iron, carbon,
and sulfur
3.2 Igneous Rocks
As molten rock cools, minerals crystallize and form
igneous rocks.
Extrusive igneous
rocks cool quickly
at Earth's surface.
Intrusive igneous
rocks cool slowly
within Earth.
What type of igneous rock has larger
mineral crystals?
A. Intrusive, because it cools more slowly
B. Extrusive, because it cools more quickly
C. Volcanic, because of the gas present
D. Sediment, because there’s more layers
Intrusive
 Cools in the earth more
slowly
 Larger Mineral Crystals
 Examples: granite and
gabbro
 When surface rock wears
away, intrusive rock can
surface; it is harder and
lasts longer
Extrusive
 Cools on earth’s surface
quickly
 Small mineral crystals or none
at all
 Examples: scoria, pumice,
obsidian
 Low silica = flows easy;
volcanoes with gently
sloping sides (Hawaiian
islands)
 High silica = cone shaped
volcanoes with steep sides
The color igneous rocks is determined
by how much silica is in it.
A. Yes
B. No
Composition of Igneous Rocks
 Most are made of silicates
 High in silicates = light color
 Low levels of silicates = dark color
As a rock gets buried deeper in the earth,
which of the following does NOT happen?
A. It can get melted into magma.
B. It can turn into sediment.
C. It can start the process of foliation.
D. More mica can start to form.
Why do rocks change as they get
buried deeper?
 Increased heat
 Increased pressure
3.4
Metamorphic rocks form as existing rocks change.
recrystallization
Metamorphic rocks form as the structure of the parent
rocks change and as their minerals recrystallize.
The process by which bonds
between atoms in minerals
break and re-form in new ways
during metamorphism.
heat and pressure
shale
schist
foliation
The arrangement of minerals
within rocks into flat or wavy
parallel bands; a characteristic
of most metamorphic rocks.
 Main PROCESS that
What is the third type of
rock called?
SEDIMENTARY
makes sedimentary
rock…
 “WETDC”
 Weathering
 Erosion
 Transportation
 Deposition
 Cementation
What is true about limestone?
A. It is made from water evaporating.
B. It is made from shells.
C. It only forms in the desert.
3.3
Sedimentary rocks form from earlier rocks.
Layers of sedimentary rocks form as
sediment
• sediments are pressed or cemented together
• dissolved minerals re-form as water evaporates
Limestone: forms when shells
are cemented together and
some of the minerals dissolve
and reform. (reacts with acid
because of the calcite)
Fossils: are found only in
sedimentary rocks
Where would a conglomorate sedimentary
rock most likely be formed?
A. Where a river is moving rapidly.
B. Where a river is moving slowly.
C. In the ocean.
Different types of sedimentary rocks
form because of the speed of the
water.