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Earth Science,
12e
Minerals: Building
Blocks of Rocks
Chapter 2
Minerals: the building
blocks of rocks
Definition of a mineral
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Natural
Inorganic
Solid
Possess an orderly internal structure of atoms
Have a definite chemical composition
Mineraloid – lacks an orderly internal
structure
Composition and
structure of minerals
Elements
• Basic building blocks of minerals
• Over 100 are known
Atoms
• Smallest particles of matter
• Have all the characteristics of an element
Periodic Table of the
Elements
Figure 2.4
How atoms are constructed
Nucleus – central part of an atom that
contains
• Protons – positive electrical charges
• Neutrons – neutral electrical charges
Energy levels, or shells
• Surround nucleus
• Contain electrons – negative electrical
charges
Simplified view of the atom
Figure 2.5
How atoms are constructed
Atomic number is the number of protons in
an atom’s nucleus
Bonding of atoms
• Forms a compound with two or more
elements
• Ions are atoms that gain or lose electrons
Isotopes
• Have varying number of neutrons
How atoms are constructed
Isotopes
• Have different mass numbers – the sum of the
neutrons plus protons
• Many isotopes are radioactive and emit
energy and particles
Minerals
Physical properties of minerals
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Habit
Luster
Color
Streak
Hardness
Cleavage
The mineral quartz often
exhibits good crystal shape
Figure 2.21
Pyrite (fool’s gold) displays
metallic luster
Figure 2.11
Mohs scale
of hardness
Figure 2.13
Three examples of cleavage –
halite, calcite, and fluorite
Figure 2.15 B
Minerals
Physical properties of minerals
• Fracture
• Specific gravity
• Other properties
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Taste
Smell
Elasticity
Malleability
Conchoidal fracture
Figure 2.16
Minerals
Physical properties of minerals
• Other properties
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Feel
Magnetism
Double refraction
Reaction to hydrochloric acid
Minerals
A few dozen minerals are called the rockforming minerals
• The eight elements that compose most rockforming minerals are oxygen (O), silicon (Si),
aluminum (Al), iron (Fe), calcium (Ca), sodium
(Na), potassium (K), and magnesium (Mg)
• Most abundant atoms in Earth’s crust are
oxygen (46.6% by weight) and silicon (27.7%
by weight)
Composition of
continental crust
Figure 2.19
Minerals
Mineral groups
• Rock-forming silicates
• Most common mineral group
• Contain the silicon-oxygen tetrahedron (molecule)
• Four oxygen atoms surrounding a much
smaller silicon atom
• Combines with other atoms to form the various
silicate structures
The silicate (SiO4
molecule
Figure 2.20
4–
)
Minerals
Mineral groups
• Rock-forming silicates
• Groups based on tetrahedral arrangement
• Olivine – independent tetrahedra
• Pyroxene group – tetrahedra are arranged in
chains
• Amphibole group – tetrahedra are arranged in
double chains
Hornblende – a member of
the amphibole group
Figure 2.21
Minerals
Mineral groups
• Rock-forming silicates
• Groups based on tetrahedral arrangement
• Micas – tetrahedra are arranged in sheets
• Two types of mica are biotite (dark) and
muscovite (light)
• Feldspars – Three-dimensional network of
tetrahedra
Minerals
Mineral groups
• Rock-forming silicates
• Groups based on tetrahedral arrangement
• Feldspars
• Two types of feldspar are Orthoclase and
Plagioclase
• Quartz – three-dimensional network of
tetrahedra
Potassium feldspar
Figure 2.21
Minerals
Mineral groups
• Rock-forming silicates
• Feldspars are the most plentiful mineral group
• Crystallize from molten material
• Nonsilicate minerals
• Major groups
• Oxides
• Sulfides
Minerals
Mineral groups
• Nonsilicate minerals
• Major groups
• Sulfates
• Carbonates
• “Native” elements
Common nonsilicate
mineral groups
Table 2.1
Minerals
Mineral groups
• Nonsilicate minerals
• Carbonates
• A major rock-forming group
• Found in the rocks limestone and marble
• Halite and gypsum are found in sedimentary rocks
• Many have economic value
Minerals
Mineral resources
• Reserves are already identified deposits
• Ores are useful metallic minerals that can be
mined at a profit
• Economic factors may change and influence a
resource
An underground
halite (salt) mine
Figure 2.22