Questions and Answers of Earth Materials Introduction To Mineralogy And Petrology

Why does the melting point of hydrous rock decrease with increasing pressure?
Why does the melting point of anhydrous rock increase with increasing pressure?
What is the latent heat of fusion, and why does it limit the amount of melting that takes place in the Earth?
What plate tectonic settings provide the conditions for the three different melting mechanisms of mantle peridotite, and what composition magmas are generated at each?
If the geotherm is normally well below the beginning of melting temperature of anhydrous mantle peridotite, what three mechanisms can cause melting of this peridotite?
How do we know that the upper mantle is composed of peridotite?
What is the evidence that Earth’s crust and mantle are normally solid?
What is an isochron and how does it give you both an age and an initial isotopic content of the daughter isotope on which the age is based?
What mechanisms must be involved in the decay of 232 Th to 90 202Pb ? 82
What four ways can radioactive nuclides decay?
What is the size of that same Mg2+?
What is a coordination polyhedron?
What is meant by coordination number (C.N.)?
Another mineral has H = 10 and perfect octahedral cleavage. Which is this?
A mineral is listed as having H = 1 and excellent planar cleavage. What mineral is this?
What mineral groups tend to have high values of specific gravity?
Specific gravity (or density) is a function (1) of an atomic property as well as (2) a crystal structure arrangement? What are these?
Metallic and nonmetallic minerals respond very differently to a hardness test. What are these differences?
What is the name of the relative hardness scale? What is the range of numbers on that scale?
Members of the mineral group mica have perfect planar cleavage – how does that show it self?
Halite has excellent cubic cleavage – what does that mean?
What is asterism?
What is meant by the term labradorescence?
If in white light a specific mineral specimen exhibits a yellow-green color (e.g., the gem olivine named peridot), which part of the optical spectrum is least absorbed?
What general distinction can you make between the igneous rocks of the ocean floor and those of the continental crust?
What sedimentary rock do we make the greatest use of in the modern world?
What feature characterizes most regionally metamorphosed rocks?
Where does the largest production of new rock take place on Earth?
What is meant by the term chromophore elements?
What is meant by vitreous?
What distinguishes metallic from nonmetallic luster?
What is meant by each of the following adjectives: prismatic, acicular, dendritic, granular, botryoidal, and oolitic?
Trace the role played by water and carbon dioxide in metamorphic rocks in going from their formation near midocean ridges to the production of granite by partial melting of continental crust above
What plate-tectonic processes deflect isotherms up or down in the Earth?
How are shallow epeiric seas that flood continents related to plate tectonics?
From where do mantle plumes derive their heat?
Why are the sedimentary rocks of rift valleys commonly red-colored and still contain a considerable amount of the relatively soft mineral feldspar?
What is the source of sediment in forearc basins and what is a common characteristic of these sedimentary beds?
Why are granite batholiths common above subducting tectonic plates?
What common volcanic rock forms above subducting tectonic plates, and what role does water play in its origin?
Water plays what important roles when circulating through fractures in newly formed oceanic crust?
Give brief definitions of igneous, sedimentary, and metamorphic rocks, and describe how you might distinguish between them.
What single process has been operating continuously since the beginning of the Earth and has been responsible for the formation of most rocks and drives plate tectonics.
From a geological map of the area where you live, determine how many rock-forming periods your home area has experienced and approximately what fraction of geologic time these periods represent.
What is the difference between a rock’s texture and structure?
What is a rock, and how does it differ from a mineral?
What is a crystal, and does the crystalline state require that crystal faces be present?
On what basis are minerals classified into different chemical groups, and of these, which forms the largest group?
Can minerals be synthesized in the laboratory?
Although the cation to anion ratio in garnet is fixed, what allows it to have a wide compositional range, and why are such widely different compositions still classified as the same mineral?
How does the arrangement of silica tetrahedra in the crystal structures of quartz and talc differ?
What are some common uses for the mineral quartz (SiO2)?
What is the composition, shape, and electrical charge on the basic building unit of all silicate minerals?
Why does table salt (NaCl) break into cube like cleavage fragments?
The following questions relate to magma of composition y in Figure 8.15(B). Figure 8.15(B).a) What mineral first crystallizes from this magma? b) When the magma first arrives at the cotectic, what
Discuss the differences between hype solvus and sub solvus granites, and explain why sub solvus granites are less likely to rise to the surface than hype solvus granites.
What evidence indicates that magmas are rarely superheated?
What is a porphyritic rock, and what does it tell you about the composition of the magma from which it formed relative to the eutectic composition?
Why is the eutectic of importance in determining the composition of magmas?
If you were able to lower a thermocouple into a cooling and crystallizing lava to measure its temperature, how might you detect when that lava reached a eutectic temperature?
When ice changes to water, the entropy obviously increases because of the more random structure of water. However, unlike almost all other solid to liquid transitions, water has a smaller volume than
Lava, on crystallizing and cooling to ambient temperature, shrinks and commonly develops polygonal fractures (Fig. 10.14). According to the sign convention used in this book for work (W), does the
Is a steaming cup of hot coffee a closed or open system, where the cup defines the boundary of the system? Explain your answer.
What is the name of the symbolic notation that is printed above the illustrations of the various crystal structures?
What are the names of two sulfides that occur as accessory minerals in igneous rocks?
What are the names of three metallic oxides that may be present in igneous rocks as accessory minerals?
What is a unique aspect of the crystal structure of tourmaline?
The mineral tourmaline is most commonly black (schorl), but several gem varieties have very different colors. Why do tourmalines have so many different colors?
Give the chemical formula for zircon. Many zircons are described as metamict. What is meant by that?
Give the end-member compositions of the olivine series. What is meant by the gem name peridot?
The t-o-t layer in muscovite is described as dioctahedral; that in phlogopite is described as trioctahedral. What is the difference?
What distinguishes the crystal structures of micas from those of the pyroxenes and amphiboles?
What are three common igneous members of the mica group?
What are three common igneous silicates that tend to be dark green in color?
How do the structures of pyroxenes and amphiboles differ?
What are three common igneous pyroxenes?
To what silicate group do nepheline and leucite belong?
How do the crystal structures of nepheline and leucite differ from those of the feldspars?
What are three colored gem varieties of quartz?
Which of these represent high-temperature forms of SiO2, and which represent highpressure forms?
The most common occurrence of SiO2 is as quartz. What are the names of the other four polymorphs?
What is a highly diagnostic physical property of the plagioclase series?
What are the end-member formulas of the plagioclase feldspar series?
How do these three differ in atomic structure, and what is the main factor that controls these structures in the first place?
What are the three polymorphs of K-feldspar?
In what components are the chemical analyses of silicates most commonly expressed?
What are the differences between major, minor, and trace elements?
A centered biaxial optic axis figure has a curved isogyre extending from the northwest to southeast quadrants and is convex toward the northeast quadrant. On inserting a first order red interference
If you have a centered uniaxial optic axis figure (a cross) and you insert a first-orderred interference filter and the northwest and southeast quadrants turn blue and the northeast and southwest
All micas are length slow. What does this mean, and what test could you apply with an interference filter to check that a grain is length slow?
When a mineral is in extinction, what can we say about the orientation of its fast- and slow-vibration directions?
What is a first-order-red interference filter and what is the normal orientation of its fast- and slow-vibration directions?
Why does the order of the interference color increase as the birefringence increases?
Why do birefringent minerals create interference colors under crossed polarizers?
What materials are isotropic?
Why does the Becke line move into the mineral of higher refractive index when the microscope stage is lowered (distance between stage and lens increases)?
What is the refractive index of a mineral?
What was Henry Sorby’s contribution to the development of the microscope?
How many polymorphs are there for Al2SiO5? Give their mineral names.
What happens in the polymorphic transition from high to low quartz?

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