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Essentials of
Physical Geology
5th Edition
Reed Wicander | James S. Monroe
academic.cengage/com/earthsci
Chapter 3
Minerals
The Building
Blocks of Rocks
Introduction
What is a mineral?
A mineral is
Naturally
Inorganic
Crystalline solid
Characteristic physical properties
Specific chemical composition.
Gemstones – precious or semi-precious minerals or rocks
used for decorative purposes
Fig. 3.1 a, p. 62
Introduction
Are amber and pearls minerals?
 Amber is considered a semiprecious “stone,” but it is not a
mineral because it is organic and not crystalline.
 Pearls, although they grow in mollusks, are minerals
because they are crystalline and meet the other criteria for
minerals.
Fig. 3.1 b-c, p. 62
Matter – What is It?
 Atoms and Elements
All matter is composed of chemical elements,
which are themselves composed of atoms.
Atoms consist of a nucleus, of protons and
neutrons, and electrons that circle the nucleus.
Elements are defined on the basis of the
number of protons in the nucleus of an atom
(i.e., the atomic number).
Another characteristic of an atom is its atomic
mass, the sum of the numbers of protons and
neutrons in the nucleus.
Matter – What is It?
 What are the atomic number and atomic mass of an atom?
 The number of protons in an atom’s nucleus determines its atomic
number, whereas an atom’s atomic mass number is the total
number of protons and neutrons in the nucleus.
 For example, if an atom has 6 protons and 8 neutrons its atomic
number and mass numbers are 6 and 14, respectively.
Fig. 3.4, p. 64
Nucleus
6p
6n
12C
(Carbon 12)
6p
7n
13C
(Carbon 13)
6p
8n
14C
(Carbon 14)
Stepped Art
Fig. 3-4, p. 64
Matter – What is It?
Bonding and Compounds
 Atoms are joined to one another
by forces known as bonding.
 Atoms of different elements
which are bonded to one another
form compounds.
Fig. 3.5a, p. 65
Matter – What is It?
Bonding and Compounds
 Ionic Bonds - Ionic bonds transfer ions, with opposite
electrical charges attracting one another
 Halite is a compound formed by the bonding of
sodium atoms to chlorine atoms.
Fig. 3.5, p. 65
electron transfer
Sodium
atom
11 p+
11 e–
Chlorine
atom
17 p+
17 e–
Sodium
ion
11 p+
10 e–
Chlorine
ion
17 p+
18 e–
+
–
Stepped Art
Fig. 3-5a, p. 65
Matter – What is It?
Bonding and Compounds
 Covalent Bonds - Covalent bonds atoms share electrons.
Fig. 3.6, p. 66
Matter – What is It?
Bonding and Compounds
Metallic Bonds
 Metallic bonds result from extreme electron sharing.
Van der Waals bonds
 Van der Waals bonds are an extremely weak bond without
available electrons to form an attraction.
Explore the World of Minerals
Naturally Occurring Inorganic Substances
We define a mineral as naturally occurring
This excludes all synthetic substances made by man like
synthetic diamonds and rubies.
The term inorganic deserves special consideration
Animal and plant matter are not minerals
Certain organisms, however, do use minerals, like calcite
and quartz, to form their shells
Explore the World of Minerals
Mineral Crystals
 Why is it that not all mineral specimens show welldeveloped crystals but all are crystalline solids?
 As minerals form and grow, they
may merge with one another to
form a mosaic of interlocking
crystalline solids that show no
obvious crystals.
 Nevertheless, individual minerals
within this mosaic have their
atoms arranged in a specific
three-dimensional framework.
Fig. 3.8 a-b, p. 67
Explore the World of Minerals
Chemical Composition of Minerals
By definition native
elements are made up of
only one chemical element,
such as gold (Ag) and
diamond (C).
Most minerals are
composed of two or more
chemical elements, such
as quartz (SiO²).
Geo-inSight 6., p. 73
Mineral Groups Recognized by Geologists
 How Many Minerals Are There? Even though there are 92
naturally occurring elements, only 8 of them are very common in
Earth’s crust.
 Even among these 8, oxygen and silicon are by far the most
common.
 Most common minerals are made up of oxygen, silicon, and
one or more other elements.
Fig. 3.10, p. 69
Mineral Groups Recognized by Geologists
 Most of the more than 3,500 known minerals are silicates
(compounds of silicon and oxygen, and other elements).
 Additional common mineral groups include carbonates,
oxides, sulfides, sulfates, and halides.
Table 3.1, p. 69
Mineral Groups Recognized by Geologists
Silicate Minerals
composed of the silica tetrahedra
Fig. 3.12, p. 70
Mineral Groups Recognized by Geologists
Silicate Minerals
 Ferromagnesian silicates - made up of iron, magnesium, or
both combined with other elements.
dark in color and dense
Fig. 3.12 a, p. 70
Fig. 3.13 a, p. 74
Mineral Groups Recognized by Geologists
Silicate Minerals
 Nonferromagnesian silicates - lack iron and magnesium
light colored
Fig. 3.11, p. 70
Fig. 3.13 b, p. 74
Mineral Groups Recognized by Geologists
Carbonate Minerals
 All carbonate minerals have the carbonate radical (CO³)-²
as in calcite (CaCO³) and dolomite [CaMg(CO³)²].
 Carbonate minerals are found mostly in the sedimentary
rocks limestone and dolostone.
 Carbonates are derived from the shells and hard parts of
marine organisms or are precipitated from seawater as
evaporites.
Fig. 3.11, p. 70
Fig. 3.14, p. 75
Mineral Groups Recognized
by Geologists
Other Mineral Groups
Native Elements
All native elements are
composed of a single
element.
Gold, copper and
diamonds commonly
occur as native
elements.
Geo-inSight 6., p. 73
Mineral Groups Recognized by Geologists
Other Mineral Groups
Sulfides
All sulfide minerals contain sulfur plus a metallic
element as in galena (PbS) and pyrite (FeS²).
Sulfide minerals are found in all types of rocks.
They commonly form along mid-oceanic ridges
Fig. 3.14b, p. 75
Fig. 3.15a, p. 78
Mineral Groups Recognized by Geologists
Other Mineral Groups
Sulfates
All sulfate minerals have the
sulfate radical (SO4 -² ) as in
gypsum (CaSO4 2H2O)
Sulfate minerals are common in
deserts, forming from evaporation
of water
Fig. 3.11, p. 70
Physical Properties of Minerals
 Mineral composition and structure produce unique
physical properties.
Color
Hardness
Cleavage
Crystal form
Specific gravity
p. 60
Physical Properties of Minerals
Luster and Color
Luster is the quality and intensity of light reflected from
a mineral and is characterized as metallic or
nonmetallic.
Color, in contrast, is a visual quality of minerals that
results from the way they absorb or transmit light.
Fig. 3.15a, c, p. 78
Physical Properties of Minerals
Crystal Form
Crystal form is useful for the identification of
minerals that typically show well-developed crystals.
For many other minerals, however, the crystals grow
in proximity to form a crystalline mass, in which case
other mineral properties such as luster, hardness,
and cleavage must be used for identification.
Fig. 3.7, p. 67
Physical Properties
of Minerals
Cleavage and Fracture
Mineral cleavage refers to the
breakage or splitting of mineral
crystals along one or more
smooth planes determined by
atomic structure.
When used with other mineral
properties, cleavage can
distinguish between minerals that
otherwise look much the same.
Fracture refers to the irregular
breakage of a mineral
Fig. 3.16, p. 79
Cleavage
in one direction
Cleavage plane
Micas—biotite
and muscovite
Cleavage in
two directions
at right angles
Potassium
feldspars,
plagioclase
feldspars
Cleavage in
three directions
at right angles
Halite,
galena
Cleavage in
three directions,
not at right angles
Calcite,
dolomite
Cleavage in
four directions
Fluorite,
diamond
Cleavage in
six directions
Sphalerite
Stepped Art
Fig. 3-16, p. 79
Physical Properties of Minerals
Hardness
 Mohs hardness scale
Ten minerals are used to
compare the hardness
between all the rest.
Table 3.2, p. 79
Physical Properties of Minerals
Specific Gravity (Density) - The specific gravity
is a way to describe how heavy a mineral is.
Specific gravity is the ratio of the weight of a
mineral to an equal volume of water.
 For example, galena has a specific gravity of 7.58 gm/cm3.
It is 7.38 times as heavy as an equal volume of water.
Fig. 3.14b-c, p. 75
Physical Properties of Minerals
Other Useful Mineral Properties
Feel - talc
Taste - halite
Magnetism - magnetite
Double refraction - calcite
React to dilute hydrochloric acid – calcite, dolomite
Rock-Forming Minerals
 How do rock-forming minerals differ from
accessory minerals?
A few minerals are
common enough to be
known as rock-forming
minerals. Most of these
are silicates.
Accessory minerals can
be ignored in this
endeavor because they
are present in minor
quantities.
Table 3.3, p. 80
Rock-Forming Minerals
Common rock forming minerals
Fig. 3.19, p.80
How Do Minerals Form?
 As molten rock material known as magma (lava at the
surface) cools, minerals begin to crystallize and grow
 This determines the composition of various igneous rocks.
Fig. 3.19, p. 80
Natural Resources and Reserves
How does a resource differ from a reserve?
A resource is any solid, liquid, or gaseous
substance in rocks whose profitable extraction is
potentially feasible. Many resources are
concentrations of economically important
minerals.
A reserve is only that part of the resource base
that can be extracted economically.
Natural Resources and Reserves
While the United States is dependent on imports for
many mineral resources, Canada is more self-reliant.
Fig. 3.20, p. 81
Natural Resources and Reserves
What factors affect the status or a resource?
Market price is the most obvious determinate of
whether a commodity is classified as a resource
or reserve
Other factors include geographic location, labor
costs, and developments in science and
technology.
End of
Chapter 3