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Chapter
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Matter and Minerals |
2
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Matter and Minerals begins by formally defining a mineral, followed by an explanation of the difference between a mineral and a rock. Mineral composition is discussed along with atomic structure, which includes an explanation of elements, atoms, compounds, ions, and atomic bonding. Also investigated are isotopes and radioactivity. Following descriptions of the properties used in mineral identification, the silicate and nonsilicate mineral groups are examined. The chapter concludes with a discussion of mineral resources, reserves, and ores.
Learning Objectives
After reading, studying, and discussing the chapter, students should be able to:
- List the definitive characteristics that qualify certain Earth materials as minerals.
- Explain the difference between a mineral and a rock.
- Discuss the basic concepts of atomic structure as it relates to minerals.
- Compare and contrast the different types of chemical bonding.
- Explain what an isotope is and how it relates to radioactive decay.
- List and discuss in some detail the various physical properties of minerals.
- Explain the structure and importance of silicate minerals.
- List the common rock-forming silicate minerals and briefly discuss their physical properties.
- List other mineral groups and give an example of the important nonsilicate minerals.
- List the economic use of some nonsilicate minerals.
- Distinguish between mineral resources, reserves, and ores.
Chapter Outline___________________________________________________________________
- Minerals: The building blocks of rocks Smallest particles of matter
- Mineral: definition Retains all the characteristics of an
- Naturally occurring element
- Inorganic Atomic structure
- Solid Nucleus, which contains
- Orderly internal structure Protons – positive electrical
- Definite chemical structure charges
- Rock: a solid, natural mass of mineral, Neutrons – neutral electrical or mineral-like, matter charges
- Electrons
- Mineral: definition Retains all the characteristics of an
- Composition of minerals Surround nucleus
A . E ments le b. Negatively charged zones called
- Basic building blocks of minerals energy levels, or shells
- Over 100 are known (92 naturally Atomic number is the number of
occurring) protons in an atom’s nucleus
- Atoms
Copyright © 2012 Pearson Education, Inc.
8
- Bonding
- Forms a compound with two or more elements
- Ionic bonds
- Atoms give up or gain valence electrons to form ions
- Anion – negatively charged due to a gain of an electron(s)
- Cation – positively charged due to a loss of an electron(s)
- Ionic compounds consist of an
- Atoms give up or gain valence electrons to form ions
orderly arrangement of oppositely charged ions
- Covalent bonds
- Atoms share electrons
- g., The gaseous elements
oxygen (O2) and hydrogen (H2)
- Other bonds
- Both ionic and covalent bonds may occur in the same compound
- Metallic bonding – valence electrons are free to migrate
- Isotopes and radioactive decay
- Mass number – the sum of the neutrons plus protons in an atom’s nucleus
- Isotope – variants of the same element with more than one mass number
- Some isotopes have unstable nuclei and emit particles and energy in a process called radioactive decay
- Physical properties of minerals
- Crystal form
- External expression of the orderly internal arrangement of atoms
- Crystal growth is often interrupted because of competition for space
- Luster
- Appearance of reflected light
- Two basic types
- Metallic
- Nonmetallic
- Color
- Often an unreliable diagnostic property
- Varieties of colors
- Exotic coloration
- Inherent coloration
- Streak
- Crystal form
Chapter 2 –
- Color of a mineral in its powdered form
- Helps to distinguish metallic luster
- Hardness
- Resistance of a mineral to abrasion or scratching
- Mohs scale of hardness
- Cleavage
- Tendency to break along planes of weak bonding
- Described by
- Number of planes
- Angles at which the planes meet
- Fracture
- Absence of cleavage when broken
- Types
- Irregular
- Conchoidal
- Specific gravity
- Ratio of the weight of a mineral to the weight of an equal volume of water
- Can be estimated by hefting the mineral
- Other properties
- Taste
- Smell
- Elasticity
- Malleability
- Feel
- Magnetism
- Double refraction
- Reaction to hydrochloric acid
- Mineral groups
- General characteristics
- Nearly 4000 minerals have been named
- Rock-forming minerals
- No more than a few dozen
- Make up most of the rocks of
Earth’s crust
- Composed essentially of the eight
elements that represent over 98 percent (by weight) of the
continental crust
- Oxygen (O) (46.6% by weight)
- Silicon (Si) (27.7% by weight)
- Aluminum (Al)
- Iron (Fe)
- Calcium (Ca)
- Matter and Minerals Sodium (Na)
- Potassium (K)
- Magnesium (Mg)
- Silicates
- Most common mineral group
- Contain silicon-oxygen tetrahedron
- Four oxygen ions surrounding a much smaller silicon ion
- Complex ion with a negative four
(-4) charge
- Other silicate structures
- Tetrahedra join to form
- Single chains
- Double chains 3. Sheets, etc.
- Negative structures are neutralized
- Tetrahedra join to form
by the inclusion of metallic cations that bond them together
- Ions of about the same size are able to substitute freely
- In some cases, ions that interchange do not have the
same electrical charge
- Common silicate minerals
- Ferromagnesian (dark) silicates
- Olivine
- High-temperature silicate
- Forms small rounded crystals
- Individual tetrahedron bonded together by a mixture of iron and magnesium ions
- No cleavage
- Pyroxene group
- Most common member –
- Olivine
- Ferromagnesian (dark) silicates
augite
- Tetrahedra are arranged in
single chains bonded by
iron and magnesium ions
- Cleavage present
- Amphibole group
- Most common member – hornblende
- Tetrahedra are arranged in
double chains
- Cleavage present
- Biotite mica
- Tetrahedra are arranged in sheets
- Excellent cleavage in one direction
- Nonferromagnesian (light)
silicates
- Muscovite mica
- Light color
- Excellent cleavage
- Feldspar
- Most common mineral group
- Two planes of cleavage
- Three-dimensional
framework of tetrahedron d. Two different varieties of feldspar
- Potassium feldspar
- Plagioclase (sodium and
calcium) feldspar
- Quartz
- Composed entirely of
silicon and oxygen b. Three-dimensional framework of tetrahedron
- Clay
- Sheet structure
- Term used to describe a
variety of complex minerals
- Most originate as products
of chemical weathering
- Important nonsilicate minerals Major groups
- Oxides
- Sulfides
- Sulfates
- Native elements
- Carbonates
- Hydroxides
- Phosphates
- Carbonates
- Two most common carbonate
minerals
- Calcite (calcium carbonate)
- Dolomite (calcium/magnesium carbonate)
- Primary constituents in the sedimentary rocks limestone and dolostone
- Halite and gypsum
- Evaporite minerals
- Important nonmetallic resources
- Many other nonsilicate minerals have economic value
- Hematite (iron ore)
- The endowment of useful minerals ultimately available commerciallySphalerite (zinc ore)
- Galena (lead ore)
- Mineral resources
- Mineral resources include
- Reserves – already identified deposits
- Known deposits that are not yet economically or technologically recoverable
- Ore
Answers to “Give It Some Thought”
Chapter 2 –
- A useful metallic mineral that can be mined at a profit
- Must be concentrated above its average crustal abundance
- Profitability may change because of economic changes
- The mechanisms that generate igneous, sedimentary, and metamorphic rocks play a major role in producing concentrated accumulations of useful elements
- a) mineral – gold is an example of a mineral classified as a native element; b) seawater is not a mineral – minerals by definition are solids; c) quartz is a mineral; d) cubic zirconia is not a mineral – it is not naturally occurring; e) obsidian is not a mineral because it lacks an internal arrangement of atoms, however, it is an igneous rock; f) ruby is a mineral – it is a gemstone variety of the mineral corundum; g) glacial ice is a mineral as it meets all of the criteria; g) amber is not a mineral since it has an organic origin.
- a) The element is uranium. b) 92 electrons c) 146 neutrons
- Sodium is more likely to form chemical bonds because of its tendency to lose one electron, resulting in an overall +1 charge.
- Potassium-39 has 19 protons and 20 neutrons; Potassium-40 has 19 protons and 21 neutrons; Potassium-41 has 19 protons and 22 neutrons
- 5 gallons of water = 40 lbs. x 20 (specific gravity of gold) = 800 lbs.
- Feldspar and quartz would be abundant in continental crust due to their relatively lower specific gravities of about 2.7. Olivine and augite would be abundant in oceanic crust since they are both ferromagnesian minerals with relatively higher specific gravities (3.2 to 3.6)
- a) hornblende b) muscovite c) quartz d) olivine e) plagioclase f) kaolinite