Download What is a mineral?

What is a mineral?
Mineral Characteristics
• A mineral is a naturally occurring, inorganic
solid with a specific chemical composition and a
definite crystalline structure.
Naturally Occurring and Inorganic
– That minerals are naturally occurring means that
they are formed by natural processes.
– All minerals are inorganic, meaning that they
aren’t alive and never were alive during any part of
their existence.
What is a mineral?
Mineral Characteristics
Definite Crystalline Structure
– A crystal is is a solid in which the atoms or molecules
are arranged in a definite pattern that is repeated over
and over again. There are 6 crystal shapes.
What is a mineral?
What is a mineral?
• Earth’s crust is composed of about 3000
minerals.
• Only about 30 minerals are common in Earth’s
crust.
What is a mineral?
Minerals Formation
Minerals form by four major processes:
1. Magma hardening
2. Changes in pressure
3. Changes in temperature
4. Formation of hydrothermal solutions
What is a mineral?
Mineral Groups
What is a mineral?
Mineral Groups
Silicates
– Silicates are minerals that contain silicon and
oxygen, and usually one or more other elements.
– Silicates make up approximately 96 percent of the
minerals found in Earth’s crust.
– The most common minerals, feldspar and quartz,
are silicates.
– Ex: Olivine is Mg2SiO4
What is a mineral?
Mineral Groups
Carbonates
– Carbonates are minerals composed of one or more
metallic elements with the carbonate compound CO3.
– Carbonates are the primary minerals found in rocks
such as limestone, coquina, and marble.
– Ex: Calcite is CaCO3
What is a mineral?
Mineral Groups
Oxides
– Oxides are compounds of oxygen and a metal.
– Hematite (Fe2O3) and magnetite (Fe3O4) are common
iron oxides and good sources of iron.
What is a mineral?
Mineral Groups
Sulfates and Sulfides
• Sulfates such as anhydrite (CaSO4) are composed
of elements with the sulfate compound SO4.
• Sulfides such as pyrite (FeS2) are compounds of
sulfur and one or more elements.
Halides
• Halides such as halite (NaCl) are made up of
chloride or fluoride along with calcium, sodium,
or potassium.
Mineral Groups
Native elements
• A native element such as silver (Ag) or copper (Cu)
is made up of one element only.
What is a mineral?
Mineral Groups
What is a mineral?
Section Assessment
1. Match the following terms with their definitions.
___
B mineral
___
C crystal
___
D magma
___
A silicate
A. minerals that contain silicon and
oxygen, and usually one or more
other elements
B. a naturally occurring, inorganic solid
with a specific chemical composition
and definite crystalline structure
C. a solid in which the atoms are
arranged in repeating patterns
D. molten material found beneath
Earth’s surface
What is a mineral?
Section Assessment
2. What are the two ways that minerals can form
from a supersaturated solution?
Mineral crystals can precipitate, or drop out of
solution if the solution becomes supersaturated.
Minerals can also form when liquid evaporates
from a supersaturated solution leaving behind
the elements which may begin to arrange
into crystals.
What is a mineral?
Section Assessment
3. Identify whether the following statements are
true or false.
_______
true
There are about 30 common minerals in
Earth’s crust.
_______
false Slowly cooling magma produces small crystals.
_______
false Coal is a mineral.
_______
true
Silicates are the most common minerals
on Earth.
_______
true
Well-defined crystal shapes are rare.
Identifying Minerals
Mineral Identification
• Geologists rely on several relatively simple tests
to identify minerals.
• These tests are based upon a mineral’s physical
and chemical properties.
• It is usually best to use a combination of tests
rather than just one to identify minerals.
Mineral Properties
• Minerals have certain physical properties that
can be used to identify them.
-color
-luster
-hardness
-streak
-density
-crystal shape
-breakage
-special properties
Identifying Minerals
Mineral Identification
Color
- Color is easy to see but not always reliable because:
a. Many minerals have same color
b. Color can change.
Identifying Minerals
Mineral Identification
Streak
Streak is the color of
powder scraped off a
mineral when it is rubbed
against a rough hard
surface. You can find
streak by rubbing a mineral
across a piece of unglazed
porcelain tile (a streak
plate).
Identifying Minerals
Mineral Identification
Luster
– Luster is the way that a mineral reflects light from
its surface.
– Metallic is shiny like a metal.
– Nonmetallic luster might be described as dull, pearly,
waxy, or silky.
Crystal Structure
• A mineral may be identified by it’s crystal
structure, one of the six previously mentioned.
Identifying Minerals
Mineral Identification
Hardness
– Hardness is a measure of how easily a mineral can
be scratched.
– We use Moh's hardness scale. We use different tools
to find the hardness- fingernail, penny, nail, glass plate
and streak plate. Diamond, the hardest, is a10. Talc,
the softest, is a 1.
– Any mineral with a greater hardness than another
mineral will scratch that softer mineral.
Identifying Minerals
Mineral Identification
Hardness
Identifying Minerals
Mineral Identification
Cleavage
– Minerals break along planes where atomic bonding
is weak.
– Cleavage is the ability of a mineral to split relatively
easily and evenly along one or more flat planes.
Fracture
– Fracture is the ability of minerals to break with rough, or
jagged edges.
Identifying Minerals
Mineral Identification
Density and Specific Gravity
– Differences in weight are the result of differences in
density, which is defined as mass per unit of volume.
– Density is expressed as a ratio of the mass of a
substance divided by its volume, or D = M/V.
– Density reflects the atomic weight and structure
of a mineral.
– The most common measure of density used by
geologists is specific gravity.
– Specific gravity is the ratio of the weight of a substance
to the weight of an equal volume of water at 4°C.
Identifying Minerals
Special Properties
• Special properties of minerals also can be used
for identification purposes.
– A type of calcite called Iceland spar causes light to be
bent in two directions, a process known as double
refraction, when it passes through the mineral.
– Magnetite, an iron ore, is naturally magnetic.
Special Properties
– Calcite (CaCO3) fizzes when it comes into contact with
hydrochloric acid (HCl).
Identifying Minerals
Mineral Uses
• Minerals are virtually everywhere.
• They are used to make computers, cars,
televisions, desks, roads, buildings, jewelry,
beds, paints, sports equipment, and medicines,
just to name a few uses.
Identifying Minerals
Mineral Uses
Ores
– An ore is a mineral that contains a useful substance
that can be mined at a profit.
– Examples of ores include Hematite, which contains
the element iron and bauxite, which contains the
element aluminum.
Identifying Minerals
Mineral Uses
Mines
– Ores are removed by underground mining or from
large, open-pit mines.
– When a mine is excavated, unwanted rock and dirt,
known as waste material, are dug up along with ore.
– If the cost of separating the waste material becomes
higher than the value of the ore itself, then the mineral
will no longer be classified as an ore because it would
no longer be economical to mine it.
– The classification of a mineral as an ore may also
change if the supply of or demand for that mineral
changes.
Identifying Minerals
Gems
• Gems are valuable minerals that are prized for
their rarity and beauty.
• Gems such as rubies, emeralds, and diamonds
are cut, polished, and used for jewelry.
• In some cases, the presence of trace elements
can make one variety of a mineral more colorful
and thus more prized than other varieties of the
same mineral.
Identifying Minerals
Section Assessment
1. Match the following terms with their definitions.
___
C streak
___
D hardness
___
B cleavage
___
A fracture
A. the ability to break with arc-like,
rough, or jagged edges
B. the ability to split relatively
easily along one or more
flat planes
C. the color of a mineral when it is
broken up and powdered
D. a measure of how easily a
mineral can be scratched
Identifying Minerals
Section Assessment
2. How would an oversupply of ore possibly
change the mineral’s classification as an ore?
If an ore is over supplied, it could drive down
prices for the ore. This may create a situation
in which it would no longer be economical to
mine material, thus the material would no
longer be classified as an ore.
Identifying Minerals
Section Assessment
3. What is specific gravity?
Specific gravity is the ratio of the weight of a
substance to the weight of an equal volume of
water at 4ºC. It is a common measure of
density used by geologists.
Chapter Resources Menu
Study Guide
Section 4.1
Section 4.2
Chapter Assessment
Image Bank
Section 4.1 Study Guide
Section 4.1 Main Ideas
• A mineral is a naturally occurring, inorganic solid with a
specific chemical composition and a definite crystalline
structure. There are at least 3000 known minerals in
Earth’s crust.
• A crystal is a solid in which the atoms are arranged in
repeating patterns. The six main crystal systems are
cubic, tetragonal, hexagonal, orthorhombic, monoclinic,
and triclinic.
• Minerals form from magma or from supersaturated
solution. Most minerals are formed from the eight most
common elements in Earth’s crust.
Section 4.1 Study Guide
Section 4.1 Main Ideas
• Oxygen readily combines with other elements to form a
diverse group of minerals, including silicates, carbonates,
and oxides. A silica tetrahedron is a three-dimensional
shape structured like a pyramid. In a silica tetrahedron
one silicon atom attaches to four oxygen atoms.
• Other major mineral groups include sulfides, sulfates,
halides, and native elements. Native elements such as
silver or copper are made of one element only.
Section 4.2 Study Guide
Section 4.2 Main Ideas
• Minerals can be identified based on their physical and
chemical properties. The most reliable way to identify a
mineral is by using a combination of several tests.
• A mineral’s color is generally the result of trace elements
within the mineral. Texture describes how a mineral
feels, and luster describes how a mineral reflects light.
Cleavage and fracture describe how minerals break.
• A mineral’s streak, hardness, and density are reliable
methods of identification. Special properties of minerals
such as magnetism also can be used for identification
purposes.
Section 4.2 Study Guide
Section 4.2 Main Ideas
• An ore contains a useful substance that can be mined at a
profit. If the cost of mining the ore becomes higher than
the value of the ore, then the mineral is no longer
classified as an ore. The classification of a mineral as an
ore may also change if the supply of or demand for the
mineral changes.
• Gems are valuable minerals that are prized for their
rarity and beauty. Trace elements can make one variety
of a mineral more valuable than other varieties of the
same mineral.
Chapter Assessment
Multiple Choice
1. What special property can be used to help
identify the mineral sphalerite?
a. It fizzles when it comes in contact with HCl.
b. It exhibits double refraction.
c. A rotten-egg odor is produced during a
streak test.
d. It is naturally magnetic.
Calcite reacts with HCl. Iceland spar and zircon exhibit
double refraction when light is passed through them.
Magnetite is naturally magnetic.
Chapter Assessment
Multiple Choice
2. A mineral with a metallic luster could be
described as ___.
a. silky
c. pearly
b. shiny
d. waxy
Silky, pearly, and waxy can all be used to describe
nonmetallic luster.
Chapter Assessment
Multiple Choice
3. Which ore is a source of iron?
a. bauxite
c. zircon
b. rutile
d. hematite
Bauxite is an aluminum ore. The ore rutile is a source
of titanium. Zircon contains no iron.
Chapter Assessment
Multiple Choice
4. A silica tetrahedron contains ___ oxygen atoms.
a. one
c. three
b. two
d. four
A silica tetrahedron is
made up of one silicon
atom bonded to four
oxygen atoms.
Chapter Assessment
Multiple Choice
5. Which of the following is an example of native
element mineral?
a. halite
c. copper
b. pyrite
d. anhydrite
A native element mineral is made up of only one element.
Halite (NaCl), pyrite (FeS2), and anhydrite (CaSO4) all
contain more than one element.
Chapter Assessment
Short Answer
6. Why are crystals that form in well-defined
shaped fairly rare?
Most crystals form in restricted space.
Chapter Assessment
Short Answer
7. What are the characteristics of minerals?
To be a mineral, a material must be a
naturally occurring, inorganic solid with a
specific chemical composition, and a definite
crystalline structure.
Chapter Assessment
True or False
8. Identify whether the following statements are
true or false.
______
true About 90 known elements occur naturally in
Earth’s crust.
______
false Oxides are compounds of oxygen and
another gas.
______
false Pyrite has a hexagonal crystal system.
______
true Ores must be mined at a profit.
______
true Rubies are more valuable than diamonds.
Image Bank
Chapter 4 Images
Tetragonal
Cubic
Orthorhombic
Hexagonal
Monoclinic
Triclinic
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