Download Chapter 4.1

Minerals
A mineral:
 Is a naturally occurring inorganic solid
 Has a specific chemical makeup
 A mineral has a specific crystalline structure
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Minerals are formed by natural processes
Minerals are inorganic (not alive EVER!!!)
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The atoms in a mineral are arranged in
particular patterns
A crystal is a solid in that has it’s atoms in a
specific repeating pattern
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Remember that solids have definite shapes
and volumes
They are primarily rigid
They also have specific unique chemical
compositions
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There are about 3000 minerals in Earth’s
crust
But only about 30 are common
About 8 to 10 are called rock forming
minerals because they make up most of the
rocks in Earths crust
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The most common elements are:
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Oxygen
Silicon
Aluminum
Iron
Calcium
Sulfur
Potassium
Magnesium
46.6%
27.1%
8.1%
5%
3.6%
2.8%
2.6%
2.1%
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Magma is less dense than the surrounding
solid rock so it can rise upward to cool.
How it cools decides what type of rock is
formed
Slowly cooled magma becomes rock with
large crystals
Quickly cooled magma has small crystals
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When a liquid gets full of a dissolved
substance, it is supersaturated
This allows minerals to form
Individual atoms bond and mineral crystals
precipitate (form into solids in the solution)
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Minerals are identified
by their chemical and
physical properties
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Crystal form
Luster
Hardness
Cleavage
Fracture
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Streak
Color
Texture
Density
Specific gravity
Special properties
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Crystal form
◦ Some minerals form distinct crystal shapes that are
immediately recognized
◦ Halite (table salt) forms perfect cubes
◦ Quartz crystals have double pointed ends and six
sided crystals
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Luster
◦ Is the way a mineral reflects light
◦ Two types of luster
 Metallic luster and nonmetallilc luster
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Hardness
◦ Is a measure of how easily a mineral can be
scratched
◦ Friedrich Mohs developed a scale to compare the
hardness of minerals
◦ Talc is the softest and Diamonds are the hardest.
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Cleavage and fracture
◦ The atomic arrangement of a mineral determines
how it will break
◦ They break along their weakest planes
◦ A mineral that splits easily and evenly along one or
more planes is said to have cleavage
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Streak
◦ A mineral rubbed across an unglazed porcelain
plate can leave a colored powdered streak on the
plate
◦ Streak is the color of a mineral when it is broken up
and powered
◦ Non-metallic minerals usually leave just a white
streak
◦ Metallic minerals leave colors although the color
may not match the solid mineral color
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Color
◦ Is caused by the presence of trace elements or
compounds within a mineral
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Define a mineral
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Describe how minerals form
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Classify minerals according to their physical
and chemical properties