Download Chapter 4 Minerals

Chapter 4
Minerals
Section 4.1 -- Page 86 - 95
Main Idea
Minerals are naturally occurring, solid, inorganic
compounds or elements.
5 Defining Characteristics of a Mineral
1. Occurs naturally
2. Is a solid
3. Is inorganic
4. Has a definite chemical composition
5. Atoms arranged in an orderly pattern
Solids With Specific
Compositions
Each type of mineral has a
chemical composition
unique to that mineral.
Example: Calcite CaCO3
Definite Crystalline Structure
The atoms of minerals
align themselves into
patterns, called a
crystalline structure.
Rock- Forming Minerals
Eight to ten of the 30 most-common minerals
are referred to as rock-forming minerals because
they make up most of the rocks in Earth’s crust.
(See Table on page 88)
Minerals From Magma
Most minerals form from
the cooling of magma (or
lava).
The longer it has to cool,
the larger the crystals that
form.
Minerals From Solutions
When water evaporates,
the minerals in solution
recrystallize.
Example: Halite (salt)
Identifying Minerals
• Geologists identify minerals using
tests based on a mineral’s physical
and chemical properties, such as:
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Crystal form
Luster
Hardness
Cleavage
Fracture
Streak
Color
Specific gravity
Texture
Density
Special properties
Luster
• The way that a mineral reflects
light from its surface.
• There are two types of luster—
• metallic luster
• nonmetallic luster
Hardness
• Hardness is a measure of how
easily a mineral can be scratched.
• Moh’s Scale of Hardness (1-10)
Mohs Scale of Hardness
Notice the use of common items for comparison:
fingernail (2.5), penny (3.5), glass (5.5), etc.…
Cleavage
The ability of a mineral to split easily and evenly
along one or more planes.
Fracture
When minerals break with rough or jagged edges.
(opposite of cleavage)
Streak
The color of a mineral when it is broken up and powdered.
Color
Most noticeable mineral characteristic…
But one of the least reliable clues of a mineral’s identity.
Texture
• Texture describes how a mineral feels to the touch.
Examples (greasy, chalky, smooth, etc.)
Special Properties
• Magnetism
• Double refraction
• Effervescence with
hydrochloric acid
• Fluorescence
• Taste (halite)
Density
• Because density is not dependent on the size or shape
of a mineral, it is a useful identification tool.
M
• Density is expressed as D 
V
• Where D = density, M = mass, and V = volume.
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