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GEOLOGY 12
CHAPTER 2 MINERALS
QUESTIONS FOR REVIEW
1.
ANSWERS
What are isotopes?
• Isotopes are atoms of the same element, having the same number of protons
(atomic number) but differing in the number of neutrons (and therefore, atomic
mass number).
2.
Compare and contrast ionic and covalent bonding.
• In an ionic material, the atoms are ions--they have gained or lost electrons to
become electrically charged--and the bonding occurs by attraction of oppositely
charged ions.
• Atoms in a covalently bonded material share electrons.
3.
How is a mineral defined? What are the two key identifying characteristics of a
mineral ?
• A mineral is a naturally-occurring, inorganic, solid element or compound, with a
definite composition or range in composition, usually having a regular internal
crystal structure.
• The composition and crystal structure are the key identifying properties.
4.
What is the phenomenon of solid solution, and how does it affect the definition of a
mineral?
• Solid solution is the substitution of ions of similar size and charge for other ions in a
crystal structure -- Fe2+ for Mg2+, for example, in the ferromagnesians.
• Solid solution accounts for the qualifier "or range in composition" in the definition.
5.
Explain the limitations of using color as a tool in mineral identification. Cite and
explain any three other physical characteristics that might aid in mineral identification.
• One mineral may occur in many different colors; also, many different minerals may
be of the-same color.
• Other properties that can be used in identification include:
Streak - the color of the powdered mineral
Luster - the surface sheen
Cleavage - the tendency to break along preferred planes
Fracture - the nature of irregular broken surfaces
Hardness - the ability to resist scratching
crystal form - or shape
6.
What is the basic structural unit of all the silicate minerals? Describe the basic
structural arrangements of the following: chain silicates, sheet silicates, and
framework silicates.
• Silicates are built of silica tetrahedra, units of one silicon atom surrounded by four
oxygen atoms.
• In chain silicates, the tetrahedra are linked in one dimension by shared oxygen
atoms.
• In sheet silicates, they are linked in two dimensions, to form sheets.
• In framework silicates, they are linked in three dimensions, with all oxygen atoms
shared.
7.
Give the compositional characteristic common to each of these nonsilicate mineral
groups: carbonates, sulfides, oxides.
• carbonates have CO3 groups, with one carbon to three oxygen atoms
• sulfides contain sulfur but not oxygen
• oxides contain oxygen but lack other constituents (carbon, sulfur, silicon, etc.)
necessary to place them in one of the other compositional groups.
8.
What is a rock?
• A rock is a solid, cohesive aggregate of grains of one or more minerals.
9.
Describe the concept of the rock cycle.
• The earth is continually changing and, likewise, rocks are subject to change
through time. Any kind of rock can be transformed into another type by the action of
appropriate geologic processes, and most rocks have been transformed many
times over the history of the earth.
Geology 12
Chapter 2
Questions For Review
Page 2
ADDITIONAL QUESTIONS (NOTES)
10.
Define and compare the properties of porosity and permeability.
• Porosity is the amount of open or void space (pores, cracks) that can be filled by
fluid; permeability is a measure of the ease with which fluids pass through a rock or
sediment.
• Permeability depends not only of the existence of porosity, but on the extent to
which pores are connected through the rock.
11.
What is the elastic limit of a solid under stress? What happens when a material is
stressed beyond its elastic limit?
• The elastic limit is the stress beyond which the material ceases to behave
elastically.
• A brittle material will rupture if stressed beyond that limit; other materials may
undergo plastic deformation. (Plastic is the behavior of materials in which
deformation is not proportional to applied stress and is permanent. The material
stays deformed when stress is removed.)
12.
The behavior of rocks under stress varies with depth. Explain briefly.
• Temperatures increase with depth. In general, cold materials tend to be more
brittle, while warmer ones may show more plastic behavior.
• Confining pressure also increases with depth, and this also increases the tendency
toward plastic behavior.
Geology 12
Chapter 2
Questions For Review
Page 3