Transcript Chapter 4: Minerals

Chapter 4: Section1
What Are Minerals?
 Minerals
– a naturally
occurring, inorganic
solid that has a
crystal structure
and a definite
chemical
composition
What 5 Characteristics Does
a Mineral Have to Have?
A mineral must be:

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Naturally Occurring
Inorganic
Solid
Crystal Structure
Definite Chemical
Composition
What Does It Mean to Be
Naturally Occurring?
A
mineral must occur
naturally
 Cement,
brick, steel, and
glass all come from
substances found in
Earth’s crust but they
are manufactured by
people
How Can Something Be Inorganic?
 Inorganic
– the mineral
cannot arise from
materials that were once
part of a living thing
 Ex. Coal is NOT a mineral
because it is made up the
remains of plants and
animals
What kind of pattern must a
mineral have?
 A mineral must have a
crystal structure – a
repeating pattern of a
mineral’s particles that
forms a solid.
 Faces – a crystal’s flat
side that meets at sharp
edges and corners
A
What kind of composition
must a mineral have?
mineral must have a
definite chemical
composition – it
always contains
certain elements in
definite proportions;
most minerals are
compounds
Cinnabar –
composed of the
elements Mercury
and Sulfur
What Is the Difference Between an
Element and a Compound?
 Element
– a substance composed of
a single kind of atom. Ex.
Hydrogen
Two or more
elements combined so that the
 Compound
–
elements no longer have distinct
properties Ex. Water H20
How Do You Identify Minerals?
 Properties:
 Density
 Crystal
Shape
 Cleavage and
Fracture
 Special
Properties
Hardness
Color
(this
can vary)
Streak
Luster
How Do You Determine a
Mineral’s Hardness?
 Friedrich
Mohs invented a
test to describe and
compare the hardness of
minerals
 Mohs Hardness Scale
Ranks ten minerals from
softest to hardest
How Does the Mohs Scale Work?
Gypsum
(2) will
scratch talc (1),
calcite (3) will
scratch gypsum
(2), fluorite (4)
will scratch calcite
(3), etc.
What Is a Streak Test?
 The
streak of a
mineral is the color
of its powder
 The streak color and
the mineral color are
often different
 To test: rub a mineral
against an unglazed
tile (streak plate)
What is the Luster of a
mineral?
 Luster
– used to describe
how a mineral reflects
light from its surface
 Minerals containing metals
are often shiny
 Earthy, waxy, and pearly
What does Density have to do
with Minerals?
 Each
mineral has a characteristic
Density
 Density – or mass per unit volume;
Density = mass/volume
 Displacement – the volume of the
displaced water equals the volume
of the the sample
What Kind of Shape does a
Mineral have?
 Minerals
have a crystal structure
 Cubic
 Hexagonal
 Tetragonal
 Orthorhombic
 Monoclinic
 Triclinic
What is Mineral Cleavage?
 Cleavage – A
mineral’s ability
to split easily
along a flat
surface
 The ability to
break apart
depends on the
arrangement of
the atoms in the
mineral
Cubic Cleavage
Basal Cleavage
What is Mineral Fracture?
 Fracture
– How a mineral
looks when it breaks apart in
an irregular way
What Special Properties does a
Mineral have?
 Fluorescence
–minerals that
glow under ultraviolet light
 Magnetism - ex. Loadstone
 Chemical Reactivity- ex. Calcite
gives off carbon dioxide
 Electrical Properties – ex. quartz
Section2:
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How are Minerals Formed?
Two General Ways:
 Crystallization of melted materials
Minerals
from Magma
 Crystallization
of materials dissolved in
water
Minerals from Hot water
solutions
Minerals
formed by
evaporation
What is Crystallization?
 Crystallization

the process by which atoms
are arranged to form a
material with a crystal
structure
How do Minerals form from
Magma?
 Minerals
form as magma
cools inside the crust, or as
lava hardens on the surface
What Effects Crystal Size?
 Rate
at which magma cools
Slower cooling forms larger
crystals
 The amount of gas the
magma contains
 The chemical composition of
the magma
How do Minerals Form from
Hot Water Solutions?
 Magma
beneath Earth’s surface
has heated the water to a high
temperature beneath Earth’s
surface causing minerals to
dissolve
 When this solution cools the
elements and compounds leave
the solution and crystallize as
minerals
What is a Solution?
 Solution
– A mixture in which
one substance dissolves in
another
What do Pure Metals often
form from Hot Water
Solutions?

Veins – A narrow channel or
mineral
slab
of a
that is much different from the
surrounding rock
How are Minerals Formed by
Evaporation?
 As
water turns to vapor it
leaves behind the mineral
 Example: A salt water solution
leaves behind large crystals of
salt
Where are Minerals Found?
 Earth’s
crust is made up of a
variety of minerals however;
rare and less common
minerals are usually located
near plate boundaries
because of volcanic activity
and mountain building
Section 3: How are Minerals
Used?
 Minerals
are the source of
Metals ex. Aluminum, Iron
Gemstones ex. Rubies and
Sapphires
Other Useful materials ex.
Talc (talcum powder)
Ore What?
 Ore
- A rock that contains a
metal or economically useful
mineral
 Most metals, gemstones, and
useful minerals must be
separated from their ores
What are the 3 Types of Mines?
 Strip
Mines – Giant equipment is
used to scrape away soil
 Open Pit Mines – Miners dig a
tremendous pit
 Shaft Mines – A network of
tunnels that extend deep
underground