59
Chapter Review
C H A P T E R
T W O
Matter and Minerals
in Review
A mineral is any naturally occurring inorganic solid that possesses an orderly crystalline structure and can be represented by
a chemical formula. Most rocks are aggregates composed of two
or more minerals.
All matter, including minerals, is composed of minute, indivisible particles called atoms—the building blocks of minerals.
Each atom has a nucleus, which contains protons (particles with
positive electrical charges) and neutrons (particles with neutral
electrical charges). Surrounding the nucleus of an atom in
regions called principal shells, are electrons, which have negative
electrical charges. The number of protons in an atom’ s nucleus
determines its atomic number and the name of the element. An
element is a large collection of electrically neutral atoms, all
having the same atomic number.
Atoms combine with each other to form more complex
substances called compounds. Atoms bond by gaining, losing, or
sharing electrons with other atoms. In ionic bonding, one or more
electrons are transferred from one atom to another, giving the
atoms a net positive or negative charge. The resulting electrically
charged atoms are called ions. Ionic compounds consist of oppositely charged ions assembled in a regular, crystalline structure
that allows for the maximum attraction of ions, given their sizes.
Another type of bond, the covalent bond, is produced when atoms
share electrons.
Isotopes are variants of the same element that have a different
mass number (the total number of neutrons plus protons found in
an atom’ s nucleus). Some isotopes are unstable and disintegrate
naturally through a process called radioactivity.
The properties of minerals include crystal shape (habit), luster,
color, streak, tenacity, hardness, cleavage, fracture, and density or
specific gravity. In addition, a number of special physical and
chemical properties (taste, smell, elasticity, feel, magnetism, double
refraction, and chemical reaction to hydrochloric acid) are useful in
identifying certain minerals. Each mineral has a unique set of
properties that can be used for identification.
Of the nearly 4000 minerals, no more than a few dozen make
up most of the rocks of Earth’ s crust and, as such, are classified
as rock-forming minerals. Eight elements (oxygen, silicon,
aluminum, iron, calcium, sodium, potassium, and magnesium)
make up the bulk of these minerals and represent over
98 percent (by weight) of Earth’ s continental crust.
The most common mineral group is the silicates. All silicate
minerals have the negatively charged silicon–oxygen tetrahedron as
their fundamental building block. In some silicate minerals the
tetrahedra are joined in chains (the pyroxene and amphibole
groups); in others, the tetrahedra are arranged into sheets (the
micas—biotite and muscovite) or three-dimensional networks
(the feldspars and quartz). The tetrahedra and various silicate
structures are often bonded together by the positive ions of iron,
magnesium, potassium, sodium, aluminum, and calcium. Each
silicate mineral has a structure and a chemical composition that
indicates the conditions under which it formed.
The nonsilicate mineral groups, which contain several economically important minerals, include the oxides (e.g., the mineral
hematite, mined for iron), sulfides (e.g., the mineral sphalerite,
mined for zinc, and the mineral galena, mined for lead), sulfates,
halides, and native elements (e.g., gold and silver). The more
common nonsilicate rock-forming minerals include the carbonate
minerals, calcite and dolomite. Two other nonsilicate minerals
frequently found in sedimentary rocks are halite and gypsum.
Mineral resources are the endowment of useful minerals
ultimately available commercially. Resources include already
identified deposits from which minerals can be extracted
profitably, called reserves, as well as known deposits that are
not yet economically or technologically recoverable. Deposits
inferred to exist, but not yet discovered, are also considered
mineral resources. The term ore is used to denote those useful
metallic minerals that can be mined for a profit, as well as some
nonmetallic minerals, such as fluorite and sulfur, that contain
useful substances.
Chapter Review
C H A P T E R
T W O
Matter and Minerals
in Review
A mineral is any naturally occurring inorganic solid that possesses an orderly crystalline structure and can be represented by
a chemical formula. Most rocks are aggregates composed of two
or more minerals.
All matter, including minerals, is composed of minute, indivisible particles called atoms—the building blocks of minerals.
Each atom has a nucleus, which contains protons (particles with
positive electrical charges) and neutrons (particles with neutral
electrical charges). Surrounding the nucleus of an atom in
regions called principal shells, are electrons, which have negative
electrical charges. The number of protons in an atom’ s nucleus
determines its atomic number and the name of the element. An
element is a large collection of electrically neutral atoms, all
having the same atomic number.
Atoms combine with each other to form more complex
substances called compounds. Atoms bond by gaining, losing, or
sharing electrons with other atoms. In ionic bonding, one or more
electrons are transferred from one atom to another, giving the
atoms a net positive or negative charge. The resulting electrically
charged atoms are called ions. Ionic compounds consist of oppositely charged ions assembled in a regular, crystalline structure
that allows for the maximum attraction of ions, given their sizes.
Another type of bond, the covalent bond, is produced when atoms
share electrons.
Isotopes are variants of the same element that have a different
mass number (the total number of neutrons plus protons found in
an atom’ s nucleus). Some isotopes are unstable and disintegrate
naturally through a process called radioactivity.
The properties of minerals include crystal shape (habit), luster,
color, streak, tenacity, hardness, cleavage, fracture, and density or
specific gravity. In addition, a number of special physical and
chemical properties (taste, smell, elasticity, feel, magnetism, double
refraction, and chemical reaction to hydrochloric acid) are useful in
identifying certain minerals. Each mineral has a unique set of
properties that can be used for identification.
Of the nearly 4000 minerals, no more than a few dozen make
up most of the rocks of Earth’ s crust and, as such, are classified
as rock-forming minerals. Eight elements (oxygen, silicon,
aluminum, iron, calcium, sodium, potassium, and magnesium)
make up the bulk of these minerals and represent over
98 percent (by weight) of Earth’ s continental crust.
The most common mineral group is the silicates. All silicate
minerals have the negatively charged silicon–oxygen tetrahedron as
their fundamental building block. In some silicate minerals the
tetrahedra are joined in chains (the pyroxene and amphibole
groups); in others, the tetrahedra are arranged into sheets (the
micas—biotite and muscovite) or three-dimensional networks
(the feldspars and quartz). The tetrahedra and various silicate
structures are often bonded together by the positive ions of iron,
magnesium, potassium, sodium, aluminum, and calcium. Each
silicate mineral has a structure and a chemical composition that
indicates the conditions under which it formed.
The nonsilicate mineral groups, which contain several economically important minerals, include the oxides (e.g., the mineral
hematite, mined for iron), sulfides (e.g., the mineral sphalerite,
mined for zinc, and the mineral galena, mined for lead), sulfates,
halides, and native elements (e.g., gold and silver). The more
common nonsilicate rock-forming minerals include the carbonate
minerals, calcite and dolomite. Two other nonsilicate minerals
frequently found in sedimentary rocks are halite and gypsum.
Mineral resources are the endowment of useful minerals
ultimately available commercially. Resources include already
identified deposits from which minerals can be extracted
profitably, called reserves, as well as known deposits that are
not yet economically or technologically recoverable. Deposits
inferred to exist, but not yet discovered, are also considered
mineral resources. The term ore is used to denote those useful
metallic minerals that can be mined for a profit, as well as some
nonmetallic minerals, such as fluorite and sulfur, that contain
useful substances.