Review for 2nd Lecture Test
Optical Mineralogy (Chapter 7)
1) What is an optic axis?† Compare and contrast uniaxial and biaxial minerals by describing differences in crystal structure and symmetry.† List the systems that belong in each group.†
2) Define and describe birefringence and the resulting interference colors.† What are the factors that control birefringence?† How is birefringence measured in minerals?† What is difference between pleochroism and birefringence?†
3) What is extinction? When and why does it occur in anisotropic minerals when viewed under cross-polarized light?† Name and describe the three types of extinction.† What are extinction angles and how are they measured?
4) Describe how the orientation of a mineral controls its birefringence.† Be able to describe which crystallographic positions produce the highest and lowest birefringence.† Describe two other important factors that control the birefringence of a mineral.
5) What are interference figures and how do they form?† Which components of the petrographic microscope are used to obtain these figures?† Define the following components of interference figures: isochromes, melatope, and isogyres.
6) List and describe the important optical properties used in identifying uniaxial minerals.† Why is refractometry more useful in identifying isotropic minerals?† Why do uniaxial minerals commonly show parallel extinction when they display elongation?† Which types of cleavage and crystal forms are not commonly seen in uniaxial minerals?
7) Compare and contrast the following uniaxial interference figures: centered optic axis, off-center optic axis, and optic normal or flash figure.† Be able to describe the visible components of each figure and crystal orientation that produces it.
8) Compare and contrast the following biaxial interference figures: acute bisectrix, centered optic axis, obtuse bisectrix and optic normal or flash figure.† Be able to describe the visible components of each figure and crystal orientation that produces it.
9) Describe how the optic sign, birefringence and indices of refraction are measured for uniaxial minerals.† Describe how the optic angle (2V), optic sign, birefringence and indices of refraction are measured for biaxial minerals.
Atomic Structure and Crystal Chemistry (Chapter 3)
1) What are the major components of the atom?† Which components account of most of the volume of the atom?† Which components account for most of the mass of the atom?† Which force holds the protons and neutrons in the nucleus?† Which force holds the electrons in orbit around the nucleus?
2) What are isotopes?† Why do isotopes display similar behavior?† How are isotopes of the same element distinguished?
3) What is the basis for the theory of Quantum Mechanics?† List and describe the four basic quantum numbers.† Explain why no two electrons will have the same quantum number.† Why are some outer subshells often filled before inner ones?† Give examples of both kinetic and potential electron energy.
4) What are valence electrons?† Define electronegativity and describe how it relates to the formation of ions and the ionization potential.
5) Define and give examples alkali metals, alkali earth metals, transitional metals, nonmetals and noble gases.† What is the difference between metals and nonmetals?
6) What are the three most important controls on the size of an atom?† What is effective size?
7) List and describe the four major types of bonds that hold minerals together.† Describe the physical properties, occurrence, and atomic radii that characterize each bond type.† What are the Coordination Principle and Coordination Number?†† For which bond type are these important?
8) Compare and contrast isodesmic and anisodesmic bonding.†† How is each bond type commonly reflected in mineral properties?
9) What are the 8 elements that are most abundant in the crust?† Describe the oxygen-based structures that form using these elements.
10) Define the following: Pauliís Exclusion Rule, coinage metals, conductance bands, and hydrogen bonds.†
Crystal Structure (Chapter 4)
1) What is the most important control on crystal structure?† Explain.
2) Describe the typical crystal structures and symmetries formed by ionic bonding.† Explain how electrostatic valency determines the nature and three- dimensional strength of the bond. Compare and contrast isodesmic, anisodesmic and mesodesmic bonding.
3) Compare and contrast the crystal structures and properties of minerals formed by covalent bonding with those formed by metallic bonding.
4) What are isostructural minerals?† Give examples.† How do they differ from polymorphs?
5) Compare and contrast the following types of polymorphs: reconstructive, displacive, and order-disorder.† Give an example of each.
6) Define solid solution.† What is the difference between simple and coupled solid solution?† Compare and contrast the following types of solid solutions: substitutional, omission, and interstitial.† Give mineral examples of each.†
7) What is exsolution and why does it occur?† Give an example of a mineral that commonly displays exsolution.
8) Describe the different ways in which mineral compositional data are shown on graphs.† What type of minerals are commonly shown on compositional plots?† Be able to determine the composition of a mineral plotted on either a linear or triangular plot.
9) Describe the procedure for writing mineral formulas relative to the order of cations and anions.