Mineralogy

Final Exam 2007


1. Draw Bowen’s Reaction series. Consider 5 mineral characteristics. Choose any you wish, they could be chemical, structural, physical, etc. Explain how the mineral characteristics follow Bowen's Reaction Series.


2. Look up the hardness of all the minerals on Bowen's Reaction Series. Is there a correlation between where a mineral plots on the series and its hardness? If so, explain why. If not, explain why not.


3. Consider these mineral groups:

silicate

native element

sulfide

halide

oxide

sulfate

phosphate

carbonate


Is there a correlation between mineral group and hardness? If so, explain why. If not, explain why not.


2. What is your favorite mineral? (If you are uncertain, choose one anyway!) Why is it your favorite? What is its formula? Does it have any economic value? If so, what is it valued for? Where (geological environment) is the mineral found?


3. Give two examples of each of the following:


Sheet Silicate:


Paired Tetrahedral Silicate:


Framework Silicate:


Ring Silicate:


Single Chain Silicate:


What examples did you choose for "Ring Silicate?" Are they really ring silicates? Most of the ones that people consider to be ring silicates don't fit perfectly into that classification. Why? Explain.


4. Remember that pegmatite you were mining from two tests ago? Wow, you have now found a vivid green crystal that is euhedral, displays multiple forms, is prismatic, is translucent and vitreous, and looks like it belongs to the hexagonal crystal system.


Define euhedral mean, forms, prismatic, translucent, vitreous?

How many forms could this crystal have?

How many crystal faces could this crystal have?

Hypothesize:

         What mineral is it?

          What element likely gave it its color?


Name three ways you could test your hypothesis and why these tests would work.


5. Why are there so few common minerals?


6. If you go collect a euhedral mineral sample and find it to be a dodecahedron, you know it has a cubic unit cell. If the specimen is an octahedron, you know it has a cubic unit cell. If the specimen is a gyroid, you know it has a cubic unit cell. Diploid, hexoctahedron . . . I could list more . . . but the question is: why must they all have cubic unit cells?


7. Explain what a polymorph is, and give some examples. Why do some minerals have polymorphs? Why do they exist? And, why do other minerals not have polymorphs?


8. Granites typically contain, at most, only 4 or 5 minerals. Same things for other kinds of igneous, metamorphic, and sedimentary rocks. Why?


9. Titanium can be found as a minor component in biotite, amphibole, and a few other common minerals. Typically, however, most titanium in a rock is found in very Ti-rich minerals such as ilmenite (FeTiO3) or rutile (TiO2). Rocks that contain significant amounts of Ti almost always contain one of these minerals. Why?


10. Why are there only 32 possible crystal classes? Why not more? Or less?


11. How do we know that minerals are composed of unit cells composed of a discrete number of atoms? How do we know that all samples of a given mineral, no matter where they come from, have the same unit cell and distribution of atoms?


12. If a tree falls in a forest and kills a geologist, would anyone make a sound?